Adaptation of multisensory integration for visuo-manual coordination during 60 days of bedrest

Adaptation of multisensory integration for visuo-manual coordination during 60 days of bedrest | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Adaptation of multisensory integration for visuo-manual coordination during 60 days of bedrest Tagliabue Michele, McIntyre Joseph, Beraneck Mathieu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7935209/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Human eye-hand coordination relies on the integration of visual and proprioceptive cues, a process influenced by gravitational inputs1. This study investigates whether the human preference for an upright head posture during visuomotor tasks results from evolutionary constraints (phylogeny) or individual adaptation (ontogeny). Volunteers completed 60 days of bedrest, performing virtual reality tests assessing their performance in cross-modal visuo-proprioceptive, unimodal visual, and unimodal proprioceptive tasks. Compared with controls, bedrest participants initially exhibited impaired cross-modal transformations, followed by partial adaptation. However, after resuming an upright posture, their responses variability and visual dependency remained greater than in controls, indicating lasting effects of prolonged head-gravity misalignment. These findings support an ontogenetic basis for the preference for a gravitationally-aligned head posture, with implications for spaceflight adaptation and vestibular rehabilitation. Biological sciences/Neuroscience Biological sciences/Psychology Social science/Psychology Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction When performing goal-oriented hand movement, like reaching to seize an object, the brain has to convert visual information about the object position and orientation into an arm and hand configuration to correctly grasp it. Because the visually-acquired target information is intrinsically encoded in a retinal reference frame and the arm configuration is mainly sensed through joint-referenced proprioceptive signals, cross-reference, visuo-proprioceptive, transformations are required 2 – 4 . The sensory processing underlying reaching tasks and the references frames in which the information is encoded has been thoroughly investigated in humans 3 , 5 , 6 . The distribution and pattern of reaching errors have been used to investigate how sensory information is encoded and transformed across multiple reference frames 7 – 9 . Studies suggest that errors in cross-reference transformations significantly influence the relative weighting of concurrent internal movement representations 6 , 10 , 11 . It was also shown that the noisiness of the cross-reference transformations, and thus their impact, can be modulated by factors such as horizontal eye and head movements 12 , 13 and by lateral head tilts 6 , 11 , 14 – 16 . In a recent study, where we investigated the short-term effects of a supine posture on visuo-manual tasks in terms of motor performances and sensory strategy, we showed a clear increase of movement errors and visual dependency, but only for tasks requiring visuo-proprioceptive transformations 1 . This result indicates that the head-vertical misalignment, and hence the alteration of gravitational, probably utricular, sensory inputs, interferes with cross-reference re-encoding. The significance of gravity in cross-modal transformations was first theorized by Paillard (1991), who proposed that the reference frames involved in visually guided movements are 'organized around the invariant vertical orientation of gravity'. Given that gravity has been one of the most consistent environmental factors throughout the evolution of our species on Earth 18 , it raises the question of whether the crucial role of utricular signals on eye-hand coordination stems from intrinsic properties of the human neural system shaped through evolution (phylogenetic origin), making them difficult to modify, or if it is a result of the brain’s lifelong adaptation to performing complex visuo-motor tasks with the head upright (ontogenetic origin). In the latter case, the observed preference for the vertical head posture may be more adaptable, although orbital visuo-manual coordination experiments showed that the gravitational ‘prior’ keep affecting astronauts’ performances for weeks 19 . To examine whether the preference for the head-gravity alignment is driven by phylogenetic or ontogenetic factors, we conducted a 60-day bedrest study with participant placed in a 6° head-down-tilt (HDT). They completed visuo-manual tasks requiring cross-modal visuo-proprioceptive (V-P) transformations, as well as unimodal visual (V-V) and proprioceptive (P-P) tasks. Their performance was compared to a control group that did not undergo bedrest. If the previously observed effects of short-term head-gravity misalignment on the V-P task 1 are ontogenetic rather than phylogenetic, we would expect that, after an initial disruption, bedrest participants would adapt to the HDT posture, gradually approaching the performance level of the control group. Results All participants successfully performed all experimental sessions, except for one control subject, who had to withdraw from the protocol for non-study-related reasons. The results from the baseline data collection (BDC), which occurred seven days before the onset of the HDT bedrest, were consistent with the observations of previous studies using a similar experimental paradigm 1 , 11 , 20 . Despite considerable inter-individual variability, parameters such as accuracy, precision, and visuo-dependency were consistently modulated by the sensory condition (see Figure S1 ). Furthermore, correlations across subsequent experimental sessions (see Table S1 ) indicate that inter-individual differences tended to persist over time, supporting both the robustness of the present experimental paradigm and the reliability of the data analyses. To account for this initial variability and isolate the effect of HDT exposure, all individual parameters measured during HDT and recovery (R) were normalized by subtracting each subject’s BDC value. In the following sections, we present the normalized results for accuracy, reflecting participants’ ability to correctly perform the task; for precision, indicating the reproducibility and robustness of their performance; and for visual-weight, describing the sensory strategy they used to achieve the task. For each of these parameters we present the results for the cross-modal (V-P) task and then for the two unimodal tasks (V-V and P-P). Accuracy Figure 1A shows the normalized total deviation ( ΔTDev ) of responses for both the Control and Bedrest groups across all experimental sessions: BDC-7 (7 days before the start of bedrest); HDT + 2, HDT + 30 and HDT + 59 (2, 30, and 59 days after the start of bedrest); and R + 2 and R + 13 (2 and 13 days after the beginning of recovery). In the cross-modal V-P task (top plot), Control participants (shaded grey) who repeated the task in an upright position, exhibited a gradual reduction in total deviation across all sessions, suggesting a learning effect. In contrast, the Bedrest group showed a different pattern: at the first session following the onset of head-down tilt (HDT + 2), their total deviation increased markedly, reflecting an initial perturbation caused by the new head/body orientation. This was followed by a progressive improvement in accuracy over subsequent sessions. As a result, a significant group difference emerged at HDT + 2, but this difference was no longer significant at later sessions (see statistics in Table 1 ), suggesting that bedrest participants partially adapted to the HDT. However, although ΔTDev values of the two groups at HDT + 30 and HDT + 59 were no longer statistically different, the Bedrest group’s accuracy did not fully reach the Control level, suggesting that their adaptation was incomplete. Even during the 13-day recovery (R) period, the accuracy of the two groups did not completely converge, suggesting a lasting after-effect of the 60-day HDT, which was not fully compensated even after two weeks in an upright posture. Changes in accuracy (TDev) can be ascribed to two main factors: the Aubert-Muller effect ( AMe ; Fig. 1B), a global shift of the responses toward/away from the direction of the lateral head-tilt; and orientation distortion ( Dist ; Fig. 1C), defined as the over/under estimation of the angular distance between targets. Figure 1B-C and Table 1 suggest that the ΔTDev differences between Bedrest and Control groups at HDT + 2 in the V-P task were more related to ΔAMe than to ΔDist . Indeed, significant differences between the two groups were observed for ΔAMe at HDT + 2 and HDT + 30, but not for the response contraction (negative ΔDist ). The between group difference in ΔAMe indicates that, while the Control group quickly learned to reduce to zero the initial (BDC-7) deviation of the responses toward the direction of the head tilt, in the Bedrest group the HDT posture initially amplified this deviation. Over the following two months, however, ΔAMe gradually decreased, reaching levels comparable to those of the Control group in the last 3 sessions. This observation provides the clearest evidence for gradual adaptation to HDT. Dist , however, followed similar patterns in both bedrest participants and controls, with both groups showing an initial contraction of responses with respect to the target spacing, followed by a similar reduction of this distortion toward zero for later sessions, though with slightly different dynamics. The combination of these two effects can explain the inter-group differences in ΔTDev shown in Fig. 1A. Both HDT and Control participants reduced the contraction effect with practice, resulting in a gradual decrease in ΔTDev for both groups, but the bedrest participants had a higher ΔTDev due to the ΔAMe induced by the HDT. The fact that bedrest participants gradually decreased both ΔAMe and ΔDist means that their ΔTDev diminishes more quickly than for controls, resulting in a gradual reduction in the inter-group difference for ΔTDev. Unlike in the cross-modal task, in the two unimodal conditions (V-V and P-P; middle and bottom plots), ΔTDev showed neither clear fluctuations over time nor significant differences between groups, even at HDT + 2. Similarly, HDT does not significantly modulate ΔAMe and ΔDist in the unimodal tasks (V-V and P-P). The acute effect of HDT on the V-P task, but not on the V-V and P-P tasks, suggests that HDT specifically interfered with participants’ ability to perform cross-modal transformations rather than with their general ability to use visual and proprioceptive information, and it supports the notion that the utilization of gravity-related signals to stabilize motor performance is a mechanism mainly engaged in cross-modal tasks. Moreover, the lack of correlation between individual modulations of accuracy parameters ( ΔTDev, ΔAMe and ΔDist ) at HDT + 2 in the cross-modal task and in the two unimodal tasks (Table 2 ) rejects the hypothesis of a link between the acute decrease in response accuracy in the V-P condition and the smaller decreases of visual and proprioceptive accuracy per se. Similarly, the gradual reduction of the between-group difference during the two-month HDT period for the V-P task, but not for the unimodal tasks, together with the lack of correlation between the session-to-session changes in the V-P and both V-V and P-P unimodal tasks (Table 2 ), suggests that HDT adaptation and the post-effect during recovery specifically involved the ability to perform cross-modal transformations. Figure 1. A) Normalized total deviation of the responses, ΔTDev , quantified as absolute distance between the average responses and the targets. B) Normalized Aubert-Muller effect, ΔAMe , corresponds to responses deviation in the same (positive values) or opposite (negative values) direction than the head tilt. C) Normalized response distortion, ΔDist , representing the over- or under- estimations (positive and negative values, respectively) of between-target distances. All three parameters are reported over the six experimental sessions for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. Given the importance of the sign for Dist and AMe interpretation, the grand mean of the BDC session has been added to the normalized values. For the Bedrest group the mean, and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively; for the Control group, by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p < 0.05 and p < 0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction. Table 1 Comparing Bedrest and Control groups for each experimental session (HDT + 2, + 30, +59 and R + 2, R + 13) and for each sensory condition (V-P, V-V and P-P). Bolded values correspond to significant Bedrest-Control differences after Benjamini-Hochberg corrections of the t-test results. HDT + 2 HDT + 30 HDT + 59 R + 2 R + 13 t (32) p t (32) p t (32) p t (32) p t (32) p V-P ΔTDev 2.96 0.0029 1.33 0.0971 1.70 0.0493 1.27 0.1062 0.96 0.1720 ΔDist 2.20 0.0177 0.92 0.1814 0.56 0.2881 -1.14 0.8686 -0.49 0.6871 ΔAMe 3.27 0.0013 2.33 0.0132 1.24 0.1129 0.57 0.2876 0.60 0.2766 ΔMSD 3.24 0.0014 2.62 0.0067 2.32 0.0135 2.34 0.0129 2.17 0.0186 Δω V 3.25 0.0013 3.74 0.0004 3.09 0.0021 2.02 0.0259 1.39 0.0875 V-V ΔTDev 0.20 0.4203 -0.79 0.7820 -0.74 0.7681 0.63 0.2671 1.18 0.1241 ΔDist 0.04 0.4843 -0.68 0.7496 -1.35 0.9062 -0.62 0.7308 1.14 0.1311 ΔAMe -1.02 0.8418 -0.57 0.7128 -0.42 0.6610 -1.61 0.9418 -1.56 0.9353 ΔMSD 0.31 0.3776 1.30 0.1019 0.76 0.2259 1.45 0.0778 2.34 0.0127 Δω V -0.64 0.7368 -1.99 0.9726 -1.99 0.9723 -1.65 0.9461 -2.19 0.9820 P-P ΔTDev 0.83 0.2056 0.82 0.2086 1.20 0.1197 0.99 0.1644 1.15 0.1295 ΔDist 0.56 0.2890 1.03 0.1563 0.67 0.2533 0.32 0.3753 -0.03 0.5104 ΔAMe 1.10 0.1396 -0.12 0.5488 0.65 0.2605 -1.24 0.8880 -0.50 0.6905 ΔMSD 1.09 0.1414 2.04 0.0246 2.03 0.0255 1.83 0.0380 1.29 0.1030 Δω V 0.18 0.4284 -1.12 0.8642 -0.92 0.8171 -1.94 0.9693 -1.80 0.9591 Table 2 For each pair of consecutive sessions, the table reports correlations between session-to-session changes in the visuo-proprioceptive (V–P) and unimodal (V–V, P–P) conditions for total deviation (TDev), Aubert–Muller effects (AMe), and response distortion (Dist). Bolded values correspond to significant correlations after Benjamini-Hochberg corrections (performed for each variable separately): none of the correlation is statistically significant. ΔTDev ΔAMe ΔDist V-P V-P V-P Bedrest Control Bedrest Control Bedrest Control R p R p R p R p R p R p HDT + 2 - BDC-7 V-V -0.03 0.89 0.21 0.66 0.57 0.01 -0.40 0.15 0.08 0.72 -0.35 0.22 P-P 0.40 0.08 0.19 0.50 0.43 0.06 0.32 0.25 -0.46 0.04 -0.11 0.71 HDT + 30 -HDT + 2 V-V 0.13 0.56 0.24 0.39 -0.09 0.69 -0.04 0.87 0.14 0.55 0.03 0.91 P-P 0.05 0.83 -0.16 0.57 0.23 0.33 0.06 0.84 -0.30 0.19 0.38 0.18 HDT + 59 - HDT + 30 V-V 0.05 0.83 0.08 0.79 0.22 0.33 0.06 0.83 -0.16 0.48 0.54 0.05 P-P -0.39 0.09 0.59 0.03 -0.11 0.62 0.08 0.79 0.26 0.27 0.07 0.79 R + 2 - HDT + 59 V-V 0.06 0.80 0.14 0.61 0.08 0.72 -0.24 0.41 -0.34 0.13 -0.16 0.58 P-P 0.24 0.31 0.35 0.21 0.24 0.30 -0.42 0.13 0.12 0.60 0.13 0.65 R + 13 - HDT + 2 V-V 0.02 0.93 -0.02 0.94 0.23 0.33 -0.12 0.67 -0.24 0.30 0.20 0.49 P-P 0.12 0.62 -0.28 0.33 -0.20 0.39 -0.26 0.37 0.15 0.52 0.09 0.77 Precision The normalized individual response variability ( ΔMSD ) showed very different time courses for the Bedrest and Control groups in the cross-modal V-P task. Figure 2A shows a clear MSD decrease between BDC-7 and HDT + 2 for Control participants. This decrease aligns with the results of our previous studies, where participants were consecutively tested in two different experimental conditions 16 , 21 , 20 , 1 : in those studies, once the main effect of the experimental manipulation was subtracted, the condition performed second was consistently associated with lower response variability than the first one, independent of the specific condition. This clear reduction in variability between the first two experimental sessions was unlikely to result from an improved ability to perform cross-modal transformations: statistical theories of multisensory integration, such as the Maximum Likelihood Principle (MLP) 6 , 11 , 22 – 26 , would predict that a reduction of the noise associated to cross-modal sensory transformations should directly result in an increase of the visual sensory weighting. However, the present increase in precision in Controls is not accompanied by a clear change in sensory strategy (see visual weight, Δω V , in Fig. 2B), nor is there a significant correlation between the individual modulations of precision and changes in visual weighting (R = 0.43, p = 0.12). Instead, as in our previous studies, this reduction in response variability among Controls is more likely explained by increased familiarity with the task/procedure and by motor learning, driven by the occasional feedback provided to sustain participants' motivation. After this initial MSD decrease, the Control group’s response variability remains quite stable, with only an additional small decrease when two experimental sessions are conducted in close succession (3 days apart between HDT + 59 and R + 2). In contrast to the Control group, the Bedrest group showed no decrease in variability between BDC-7 and HDT + 2; instead, they exhibited a slight increase. This pattern suggests that the HDT condition either masked or interfered with the early learning effect observed in Controls. Moreover, the significant correlation between individual ΔMSD and Δω V at HDT + 2 (R = -0.48, p = 0.03) supports the idea that misalignment of the head with gravity affects cross-modal processing precision: as mentioned above, statistical theories based on the Maximum Likelihood Principle (MLP) predict that changes in cross-modal transformation noise should directly influence sensory weighting. The implications of this between-group difference will be addressed in more detail in the discussion, in light of previous findings. During the two months of HDT the Bedrest group showed a fairly stable response variability. Even at the transition from the HDT to recovery (R) phase, only a small decrease in variability, similar to that of the Control group, was observed. This − 10.5° 2 drop appears considerably smaller than the − 44° 2 decrease observed in our previous short-term experiment for the participants who performed the task first in the supine and then in the seated condition 1 . The smaller amplitude here may be a consequence of the longer duration of body-gravity misalignment, which could lead to lasting interference in the participants’ ability to perform cross-modal transformations, that persisted after returning to the seated position during recovery. Although the ΔMSD of the Bedrest group considered alone did not appear to undergo large modulations, comparing it to the Controls showed strong between-group differences: the difference in the MSD modulations between BDC-7 and HDT + 2 for Bedrest and Control participants resulted in a significant group difference at HDT + 2 (see Fig. 2A and Table 1 ). This significant difference persisted, though to a lesser extent, at HDT + 30 and at HDT + 59, and even during the recovery period (R + 2 and R + 13). The persistence of the significant Bedrest-Control difference during the Recovery phase reinforces the idea that the 60-day HDT resulted in a significant after-effect on participants’ precision. Consistent with our previous study showing no acute effect of the supine posture on the unimodal tasks precision 1 , no significant difference between Bedrest and Control participants was observed at HDT + 2 in Δ MSD for either unimodal tasks (V-V and P-P). This lack of difference persisted for the whole duration of the experiment. Because in Fig. 2A the pattern of the average ΔMSD in the unimodal task appears qualitatively similar to that in the cross-modal task (especially for the Control group), we tested for possible correlations between individual session-to-session changes in MSD in the cross-modal and unimodal tasks, to further examine the hypothesis that the modulations of response variability in the V-P condition could be due to smaller, non-detectable, variations of visual and proprioceptive precision. The lack of significant correlations (see Table 3 ) does not support this hypothesis. Sensory strategy (visual weighting) The difference between the Bedrest and Control groups in the cross-modal V-P task is even more striking in terms of sensory weighting (Fig. 2B). Consistent with our previous short-term study 1 , which demonstrated a greater visual dependency in the supine than in the seated position, at HDT + 2 the visual weight (ω V ) increased substantially for the Bedrest but not for the Control participants, resulting in a significant difference between the two groups. Surprisingly, the difference between the two groups did not decrease during the two months of HDT, and even after resuming the seated posture (R + 2), the difference remained significant with only a slight reduction. After thirteen days of recovery, the difference between the two groups was still visible but no longer significant. As for the response precision and, to a lesser extent, accuracy, the persistence of a difference in visual dependency between the two groups during the Recovery period appears to be a post-effect of the two-month bedrest, suggesting that, despite the lack of change of the visual dependency during the HDT phase, the participants have adapted to the tilted posture and were unable to quickly switch back to their baseline (BDC) sensory strategy. As with all previously reported parameters, the results were very different for the unimodal tasks: for both V-V and P-P tasks, the visual weight measured for the Bedrest group showed only small variations over time and is never significantly larger than that of Controls (Fig. 2B, middle and lower panels). It is interesting to notice however, that in both unimodal conditions the visual weight of the Control group showed a qualitative tendency to increase over time. This could be due to de fact that in all sensory conditions the feedback about their responses seldomly provided to the participants to keep them motivated was visual. This might have gradually biased them toward a visual strategy. To determine whether the visual dependency changes in the V-P condition relate to the sensory strategy in the unimodal tasks, correlations between cross-modal and unimodal results are reported in the right part of Table 3 . The increase in visual weight for the Bedrest group between BDC-7 and HDT + 2 in the V-P condition appears unrelated to the Δω V in the unimodal tasks. These results suggest that the strong increase in visual dependency in the cross-modal condition is not due to some combination of the smaller, non-significant, ω V increases in the V-V and P-P unimodal conditions. This interpretation is supported by the fact that, for Control participant as well, the individual Δω V values in the V-P task are not correlated with those in the P-P condition, and are even negatively correlated with those in the V-V condition. Figure 2. A ) Normalized responses’ variability, ΔMSD , and B ) Normalized weight associated to visual information, Δω V , are reported for all six experimental sessions, for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. For the Bedrest group the mean and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively. For Controls, the same parameters are represented by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p < 0.05 and p < 0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction. Table 3 For each pair of consecutive sessions, the table reports correlations between session-to-session changes in the visuo-proprioceptive (V–P) and unimodal (V–V, P–P) conditions for response variability (MSD) and for the visual weight (ω V ). Bolded values correspond to significant correlations after Benjamini-Hochberg corrections (performed for each variable separately): none of the correlation is statistically significant. ΔMSD Δω V V-P V-P Bedrest Control Bedrest Control R p R p R p R p HDT + 2 - BDC-7 V-V -0.11 0.64 -0.20 0.50 0.06 0.78 -0.59 0.03 P-P 0.52 0.02 -0.07 0.81 -0.16 0.49 -0.24 0.40 HDT + 30 - HDT + 2 V-V 0.20 0.39 -0.20 0.49 0.05 0.82 -0.23 0.42 P-P 0.15 0.51 0.05 0.86 -0.33 0.15 -0.43 0.12 HDT + 59 - HDT + 30 V-V -0.07 0.76 -0.04 0.89 -0.14 0.54 -0.30 0.29 P-P 0.14 0.54 -0.41 0.14 0.02 0.94 -0.26 0.38 R + 2 - HDT + 59 V-V 0.52 0.02 0.40 0.15 0.11 0.65 0.05 0.86 P-P -0.11 0.62 -0.10 0.72 0.22 0.34 -0.04 0.88 R + 13 - HDT + 2 V-V 0.14 0.56 -0.45 0.10 -0.18 0.45 -0.45 0.10 P-P -0.17 0.48 -0.20 0.47 -0.04 0.85 -0.05 0.85 Discussion The present study investigated the effects on eye-hand coordination of 60 days of head-down tilt (HDT) bedrest, a space-analog, and focused on the brain’s ability to adapt to altered gravitational inputs. Our results can be interpreted across three main phases: the acute effect of HDT at its onset, participants’ adaptation during the two-month bedrest period, and the post-effects observed during recovery. Comparing the cross-modal visuo-proprioceptive (V-P) task with the unimodal tasks (V-V and P-P) allowed us to better discriminate changes in cross-modal sensory transformations from those affecting visual or proprioceptive processing alone. Acute effect of HDT : at the beginning of HDT (HDT + 2), participants showed a deterioration in performance on the V-P task, primarily as an increase in response error (accuracy loss), whereas control participants tested in the seated position did not lose accuracy and improved their precision. This acute effect replicates and extends our earlier finding that supine posture perturbs cross-modal transformations 1 . Interestingly, the increase in variability of the responses for bedrest participants’ ( ΔMSD = 2.4° 2 ) was however much smaller than the 26° 2 increase previously observed when considering only the subjects tested seated and then supine in the same day 1 . We interpret this difference as the result of two competing processes: a reduction in response variability due to task familiarization (clearly visible in the Control group), and a perturbation of cross-modal sensory transformations due to altered otolithic signals when supine. Consistent with this interpretation, in our previous short-term experiment the variability modulation was even larger (43° 2 ) for the participants tested supine and then seated and for which familiarization and posture effects sum up. Compared to our previous short-term study, participants in the present study had more time to familiarize themselves with the task completing all three experimental conditions (V-P, V-V and P-P) before the start of bedrest, which may have favored the reduction in procedural variability, and thus the almost full compensation of the posture effect. An alternative explanation for the attenuated posture effect on response precision is that HDT could have suppressed session-to-session learning, as a previous bedrest study suggested 27 . However, this interpretation is not supported by the concurrent accuracy deterioration observed here and the fact that participants in our previous short-term study 1 still displayed robust posture effects even when tested in the seated and then supine conditions. In the light of these results and considerations, the acute worsening of the Bedrest group’s performance with respect to the Control group in the V-P task likely arises from a postural effect rather than a general inhibition of motor learning. This interpretation is also consistent with findings from other visuo-manual coordination tasks, such as the Purdue Pegboard Test (PTT) during bedrest 28 , where posture selectively affected PPT execution time but not mental rotation performance, suggesting a specific impact on visuo-manual control rather than spatial representation more generally, in line with the lack of effect of the supine posture on the perception of visual and haptic objects’ dimensions 29 . The acute degradation in V-P performance of the Bedrest group with respect to the Control group, was also accompanied by a significant increase in visual dependency (ω V ), indicating a clear change in multisensory strategy. This shift aligns with our previous findings 1 and supports broader evidence for sensory reweighting as a mechanism of adaptation to altered gravitational contexts 30 . Unlike the cross-modal task, the unimodal tasks (V-V and P-P) were largely unaffected by posture both in terms of response errors and sensory strategy, highlighting that the observed deficits were specific to the ability to perform visuo-proprioceptive transformations. The absence of acute effect of posture in the V-V task is in line with results from a comparable orientation reproduction test study 31 . We note however that supine posture was reported to affect other visual tasks, such as letters identification and face recognition 32 , 33 . On the other hand, the results from the P-P task appear in contradiction with the underestimation of somatosensory stimulations reported in the only previous attempts, to our knowledge, to investigate upper-limb proprioception during HDT 34 . A possible explanation for this apparent contradiction could reside in the fact that in this previous study proprioception was assessed via electrical stimulation on passive subjects, whereas our paradigm required active movements of the arm, which may be less sensitive to postural changes due to increased muscle tone enhancing proprioceptive input. Adaptation during 60 days bedrest The longitudinal measurements obtained in this study provide a unique view of behavioral adaptation during prolonged HDT. Over the two-month bedrest, participants’ performance gradually improved, reducing the accuracy gap with controls. This recovery was primarily driven by a gradual reduction of the Aubert effect 35 - the systematic deviation of responses toward the direction of lateral head tilt - which was most pronounced during the first HDT session. This pattern suggests that the initial performance decline resulted from the inability to use gravity as an external reference for motor stabilization and that participants gradually learned to compensate for this loss. Similar roll-tilt-induced response deviations have been reported for subjective visual and tactile vertical tasks, as well as in visuo-manual reproduction tasks 36 – 38 , but to our knowledge, this is the first study to track their progressive reduction over a long-duration bedrest. In contrast to accuracy, participants’ precision did not show significant improvement during HDT. This dissociation between the time courses of constant (accuracy) and variable (precision) error components resembles the gradual visuo-motor learning process described in the literature, where accuracy improves faster than precision 39 – 41 . The fact that accuracy improvements were observed for the cross-modal V-P task, but not for unimodal tasks, indicates that, similarly to the acute effect, this learning specifically involved the re-encoding of sensory information across modalities, rather than general visual or proprioceptive performance. Despite the observed adaptation, participants never fully matched the accuracy or precision of controls, even after two months of HDT. This may indicate that a longer period of exposure would be needed to achieve complete compensation, or that certain aspects of visuo-proprioceptive transformations cannot fully recover in the absence of gravitational reference frames. This interpretation is consistent with theoretical work suggesting that referencing sensory information to gravity provides an optimal solution for cross-modal integration 6 and that its absence would lead to an unavoidable degradation in performance. Interestingly, visual dependency did not decrease during the HDT period despite the observed improvement in accuracy, and remained elevated until after the recovery period. This observation is in line with the results of classical ‘rod and frame’ test showing no significant evolutions during bedrest 28 , 42 and with the predictions from our concurrent model of multisensory integration, based on maximum likelihood principles 1 , 6 , 11 , 16 , which forecasts no change in visual weighting even if cross-modal transformation noise improves (see Supplementary Information). Thus, the persistent visual dependency should not be interpreted as a failure to adapt, but it rather represents an optimal sensory strategy. The performance of bedrest participants in the unimodal tasks (V-V and P-P) showed only small, non-significant changes throughout the HDT phase and did not differ from controls. Our observations for the V-V condition appear in line with a previous study showing no clear effects of bedrest on visual perceptual tasks other than a decrease in reliance on external visual cues 43 . This latter finding recalls the slight (non-significant) visual weight increase and decrease observed here for control and bedrest subjects, respectively. The lack of degradation of either precision or accuracy in the V-V tasks also suggests that, although the Spaceflight Associated Neuro-Ocular Syndrome (SANS) is a known potential side effect of bedrest 44 (two of the 20 participants developed SANS during the protocol), performance in the present orientation reproduction tasks were apparently not affected by possible degradations of the visual system. Our results from the P-P task, suggesting that upper-body proprioception is preserved during the two months bedrest, represent a novel dataset and it can hardly be compared to any previous results in the literature, which focused on the lower-limbs and showed a significant degradation of proprioception 45 – 48 . This difference likely relates to the fact that even during HDT, the arms continue to be used in a normal manner. Indeed, during bedrest only lower-limbs muscles face significant atrophy 49 . Interestingly, this arm-leg difference is also reflected in the semantic processing of verbs referring to lower- and upper-limb actions, with a specific effect on the semantic representation of lower-limbs actions following HDT 50 . Recovery Participants continued to display reduced precision and slightly lower accuracy relative to controls, even after returning to an upright posture. Visual dependency also remained higher than in controls for several days. These findings indicate that the adaptation to HDT persisted into recovery, consistent with prior observations using the rod-and-frame test 42 . One interpretation is that participants not only learned to down-weight gravity cues during HDT but also partially “unlearned” how to exploit them once they became available again, leading to suboptimal behavior relative to controls who never experienced prolonged tilt. This result suggests that the human preference for an upright posture during visuo-motor tasks is highly flexible and can be temporarily overwritten by experience. This apparent interference between the ability to perform transformations with and without gravitational cues aligns with the hypothesis that visuo-proprioceptive transformations are supported by recurrent neural networks in the intraparietal sulcus (IPS), which receive convergent visual, somatosensory, and vestibular inputs 1 , 29 , 51 . Prolonged HDT may induce gradual modification of the IPS synaptic connections to adapt to the altered otolithic input, similar to the functional neural connectivity changes reported in cosmonauts post-flight 52 . Consequently, during recovery the cross-modal transformations must rely on newly modified neural networks that are no longer optimized to the upright posture. In conclusion, the adaptation observed during the two-month bedrest and its subsequent effects on participants' precision and multisensory integration during the recovery period strongly support the notion that the human preference for head postures aligned with gravity during visuo-motor tasks 16 , 1 is primarily ontogenetic rather than phylogenetic, in line with animal model data showing that multisensory integration skills are not innate, but they emerge from cross-modal experiences in a specific environment 53 . In other words, this preference does not appear to be a 'hard-wired' evolutionary trait but rather the result of individual adaptation to Earth's gravitational environment, where gravity-related signals are used to enhance visuo-motor coordination. This finding has significant implications for space and planetary exploration, as well as clinical applications. It suggests that astronauts’ brains may adapt to weightlessness in ways that could hinder their visuo-manual coordination upon re-exposure to gravity, and it offers hope for rehabilitation of patients with vestibular dysfunction by highlighting the brain’s capacity to recalibrate sensory integration strategies. However, the observed persistence of differences with control subjects toward the end of bedrest indicates that full compensation may not be possible when gravity-related signals are absent, raising the question of whether alternative cues, natural or artificially provided (e.g., via augmented reality), could fully substitute for gravity signals in supporting optimal visuo-manual coordination. Methods Ethics Statement The experimental protocol was approved by the Université Paris Cité ethical committee (N° CER 2014-34/2018 − 115) and by the French ‘Comité de Protection des Personnes’ (CPP Sud-Ouest et Outre-Mer I, France, number ID RCB: 2016-A00401-50) and all participants gave written informed consent in line with the Declaration of Helsinki. Experimental Setup The participants wore Oculus Rift1 virtual reality (VR) goggles (field of view: 90◦, frame rate: 90 Hz, resolution: 1080 × 1200 pixels, adjustable inter-pupillary distance). A motion-analysis system (CODAmotion; Charnwood Dynamics, sub-millimeter accuracy, 200-Hz sampling frequency) was used for real-time recording of the position of 24 infrared active-markers. These LEDs were placed on the light-weight 3D-printed structures which were fixed to the VR headset (8 LEDs), to the subjects’ right hand (8 LEDs) and to their chest (8 LEDs) as shown in Fig. 3 A. Custom C + + code was developed by the research team to combine the information about the three-dimensional position of the infrared markers and the angular velocity of the VR headset (Oculus Rift sensors) to estimate in real-time the position and the orientation of the subject viewpoint and to update accordingly the stereoscopic images shown in the VR goggles. For tracking the hand and chest movements, only infrared markers were used. The 3D virtual scene shown to the subjects consisted of a cylindrical rocky tunnel (Fig. 3 B-C). To help the subject spatial orientation, metal tubular structures parallel to the tunnel axis were added on the walls: the tubes went from clear on the “ceiling” to dark on the “floor” facilitating the identification of the visual vertical. Experimental Paradigm The task The task performed by the subjects was similar to the one of our previous studies 1 . It can be split in three main phases: 1) acquisition of the target orientation, 2) memorization delay and 3) alignment of the hand to the memorized target. 1) In the acquisition phase the subjects had 2.5 seconds to memorize the target orientation that could be laterally tilted of − 45°, − 30°, − 15°, 0°, + 15°, + 30° or + 45° with respect to the virtual vertical. This phase was always performed with the head aligned with the trunk. 2) During the delay phase, after the target disappeared, the subjects waited 5 seconds for a visual cue prompting the response. In the first 21 trials of each sensory condition, during this phase, the subjects had to keep the head aligned with the trunk. In the following 56 trials the subjects were guided to tilt the head 15° to the right or to the left. The direction and the amplitude of the head roll to be performed was indicated by a circular arrow and semi-transparent halo spaced around the subject eyes (Fig. 3 C). The halo changed color depending on lateral tilt of the subjects’ head, going progressively from red to green when approaching the desired head orientation. If at the end of the 5 seconds delay the subjects were unable to maintain the halo green, the trial was interrupted and repeated later on, otherwise a visual ‘go signal’ appeared, indicating the transition to the following phase. 3) During the response phase the subjects had to align the hand to the memorized target, while keeping the head orientation reached after the delay phase. To validate their response the subjects had to press a button on a remote hold in the left hand. In order to quantify the sensory weighting a sensory conflict was artificially introduced in half of the trials with lateral neck flexion 11 : a gradual, imperceptible conflict was generated such that, when the subjects laterally flexed the neck, they received visual information corresponding to a larger head tilt. The amplitude of the angle between the visual vertical and subject body axis varied proportionally (by a factor of 0.6) with the actual head tilt, so that for a 15° lateral head roll a 9° conflict was generated. When, at the end of the experiment, the subjects were interviewed about the conflict perception, none of them reported to have noticed the tilt of the visual scene. Sensory Conditions The same task was performed in three distinct sensory conditions represented in Fig. 3 B. The main condition is the Cross-Modal condition aimed at investigating the brain ability to encode visual information in the proprioceptive space and vice-versa. Two unimodal conditions were performed to quantify possible effects of prolonged bedrest on Vision and Proprioception respectively. Cross-Modal (V-P) condition . The target was presented visually and during the response the hand orientation could be controlled through arm proprioception only. The target consisted of parallel blue beams placed at the end of the tunnel (three meters in front of the subject), as shown in the upper-left panel of Fig. 3 B. During the response phase, the hand of the subjects was represented as a capsule with the main axis aligned with the prono-supination axis of the hand. In this way only the arm proprioception could be used to control the prono-supination alignment task, whilst all remaining degrees of freedom of the hand, which are task irrelevant, could be also visually controlled. Uni-Modal Visual (V-V) condition. Only vision could be used for both target acquisition and response control. The target orientation was presented as blue beams as in the Cross-Modal task. During the response phase the subject kept the hand next to the body and a virtual representation of the hand (central-right part of Fig. 3 B) appeared in front of the subject eyes with a random orientation. They used the oculus remote right-left buttons to change the virtual hand roll to reproduce the memorized target orientation. Only visual information could be used to estimate the necessary response adjustments. Uni-Modal Proprioceptive (P-P) condition. Both target and response orientation could be sensed through proprioception only. The target orientation was not presented as blue beams (bottom-left panel of Fig. 3 B). To acquire the target lateral tilt, the subjects raised the hand, which was represented as a capsule, as in the response phase of the V-P task, but the color of the capsule changed from red to green when the absolute angular distance between the hand and target roll decreased. The only information available to memorize the target orientation was hence the proprioceptive feedback related to forearm pronation-supination corresponding to the capsule becoming green. After 2.5 sec with the correct hand orientation, that is with a green capsule, the subjects were instructed to lower the arm. The response was controlled using proprioception only, as in Cross-Modal (V-P) task. For each sensory condition the subject performed 21 (= 7 targets x 3 repetitions) trials without head rotations and 56 (= 7 targets x 2 head rotations x 2 conflicts x 2 repetitions) trials with lateral neck flexions. Therefore, one experimental session consisted of 231 trials and lasted up to two hours including rests between sensory conditions and breaks every 7 trials. In order to keep the subject motivated, after the response validation of 102 randomly selected trials (among those without conflict) a hand shaped projectile was casted toward the reappeared blue beams so that the subjects could estimate the accuracy of their response. Bedrest and Control protocol A group of 20 healthy male subjects (34+/-8 years hold) participated to the present experiment in the frame of a long-term bedrest campaign (LTBR) sponsored by the European Space Agency (ESA) and performed at the French Institute for Space Medicine and Physiology (MEDES), in Toulouse, France. As shown in Fig. 3 D, the LTBR protocol consisted of 15 days of baseline data collection (BDC), 60 days of -6° head down tilt (HDT) bedrest and 15 days of recovery (R). The subjects participated to a training session 14 day before the HDT phase to get used to the different tasks. They performed an experimental session in the Seated posture (upper part of Fig. 3 A) 7 days before the HDT (BDC-7). They were tested three times in the Supine posture (bottom part of Fig. 3 C) during the HDT phase: after 2, 30 and 59 days (HDT + 2, HDT + 30, HDT + 59). To perform the task in this condition the special head support described by Bernard-Espina et al. (2022) was used. Finally, they were tested in the Seated posture at day 2 and 13 of the recovery period (R + 2 and R + 13). A group of 15 control subjects (30+/-9 years hold) performed the same tasks at the team laboratory, following the same schedule than the bedrest group. This group was not constrained, however, to the HDT posture for two months and the participants continued their daily life activities for the duration of the experiment. All experimental sessions for this group were performed in the Seated posture, in order to specifically quantify possible learning effects due to the multiple repetitions of the experiment, which is known to occurs especially when feedback about the response errors is provided. Data Analyses The lateral inclination (roll) of the hand when the subject validated the response was analyzed using Matlab (MathWorks, RRID: SCR_001622). To exhaustively describe the performance of each subject several parameters have been computed from their responses. In order to maximize the robustness of the parameters despite the few responses available per each combination of target and head orientation, the procedure described below, and based on linear interpolations, has been used. First, for the trials with the head straight ( HS ) all responses ( r i ) and the corresponding targets ( t i ) are linearly interpolated (Fig. 4 A) obtaining the regression line r = m HS ·t + q HS . For the trials with lateral head tilt ( HT ) without conflict, as shown in Fig. 4 B-C, the response obtained after the rotation of the head to the right ( HR ) and to the left ( HL ) are interpolated separately but imposing their parallelism obtaining two regression line r = m HT ·t + q HR r = m HT ·t + q HL The parallelism between the regression line for the trial HS and HT is not imposed, because previous results suggest that tilting the head could affect the slope of the regression line 1 . Once computed, the coefficients of the regression lines are used to estimate all parameters describing the individual performances. For each experimental session and sensory condition, the subject precision is quantified by computing the variability of the N responses, as Mean Squared Deviation ( MSD ) from the corresponding regression lines. $$\:MSD=\frac{\sum\:_{i\in\:HS}{\left({m}_{HS}·{t}_{i}+{q}_{HS}-{r}_{i}\right)}^{2}+\sum\:_{i\in\:HR}{\left({m}_{HT}·{t}_{i}+{q}_{HR}-{r}_{i}\right)}^{2}+\sum\:_{i\in\:HL}{\left({m}_{HT}·{t}_{i}+{q}_{HL}-{r}_{i}\right)}^{2}}{N}$$ Although taking the square root of MSD would have yielded a more intuitive variability parameter expressed in degrees, this transformation would not have allowed a correct computation of between-sessions differences. As it will be shown, these differences are essential for data normalization and thus to an effective analysis of the HDT effect. The accuracy was represented by the responses’ Total Deviation ( TDev ) and computed as the average absolute distance between the responses regression lines and the line passing through the targets’ positions, represented in the following equations by the terms 15°nt , where nt identifies the target number from − 3 to + 3: $$\:TDev=\sum\:_{nt=-3}^{3}\left(\left|{m}_{HS}\left(15^\circ\:nt\right)+{q}_{HS}-15^\circ\:nt\right|+\left|{m}_{HT}\left(15^\circ\:nt\right)+{q}_{HR}-15^\circ\:nt\right|+\left|{m}_{HT}\left(15^\circ\:nt\right)+{q}_{HL}-15^\circ\:nt\right|\right)/21$$ The distortion ( Dist ) , representing possible over/under-estimation of the distance between the targets’ orientation 54 , is represented by the average angle between the regression lines and the line passing through the targets’ orientations: $$\:Dist=\frac{\left(\sum\:_{c=HS,HT}\text{atan}\left({m}_{c}\right)-45^\circ\:\right)}{2}$$ Positive and negative values of Dist correspond to a global over- and under- estimation of the angular distances, respectively. The Aubert-Müller effect ( AMe ) , corresponding to the global response bias due to the lateral neck flexion 35 , was quantified as half of the algebraic distance between the intersection point of the two HT regression lines with the vertical axis: $$\:AMe=({q}_{HL}-{q}_{HR})/2$$ Positive and negative values of AMe correspond to a global deviation of the responses in the same and opposite direction than the head tilt, respectively. Given the importance of the sign for the interpretation of the two later parameters, Dist and AMe , in the result representation the grand average of the BDC-7 session has been added to the normalized values (see statistical analyses). Sensory weighting estimation In order to quantify the relative weight associated to the visual encoding of the sensory information, the deviation of the responses due to the imperceptible tilt of the visual scene has been computed. To quantify the specific effect of the sensory conflict in each condition we linearly interpolated the responses of the trials with conflicts with right and left neck flexion constraining the lines to be parallel to regression lines of the no-conflict-trials (see Fig. 4 B-C). This procedure provides the response-axis intercepts for the conflict trials. Subtracting to these parameters the corresponding values in the no-conflict-trials we obtain the average deviations of the response due to the tilt of the visual scene: Δq r,Hi . In order to convert the response deviation into the percentage weight given to visual information, we computed, for each conflict trial, the virtual displacement of the target expected if only visual information was used to code its orientation, which corresponds to -head_angle × 0.6 . We linearly interpolated these theoretical responses for right and left neck flexion separately, constraining the lines to be parallel to the one joining the targets ( m = 1) and we obtained the vertical axis intercepts. Subtracting from these parameters the intercept of the line joining the target in the no-conflict trials ( q = 0), we obtain the average target deviation expected in case of fully visual encoding of their orientation: Δq t,Hi . The percentage weight given to the visual information, ω V , can be then computed as it follows: $$\:{\omega\:}_{V}=\frac{1}{2}\sum\:_{d=L,R}\frac{\varDelta\:{q}_{r,hi}}{\varDelta\:{q}_{t,hi}}\bullet\:100\%$$ Statistical analyses In order to compensate for initial between-subjects’ differences, as for instance subject sensory acuity or motor precision, all results are expressed as a difference (Δ) with respect to BDC-7 session, which results in a normalization of the results. Then, in order to specifically quantify the effect of the bedrest, for each following session we compared the distribution of the results of the Bedrest subjects with respect to the corresponding Controls’ session. As the parameters resulted normally distributed (Anderson-Darling test) the comparison between the Bedrest and Control groups were performed by using parametric independent t-tests. The one-tailed version of this test was employed, since our previous experimental study on the acute effects of the supine posture 1 and our optimal sensory integration theory 6 , 11 , 21 provide very clear hypotheses on the expected effects of the bedrest: increase of all the computed parameters (response variability, MSD ; response total deviation, TDev ; visual weight, ω V ; Distortion, Dist ; and Aubert-Muller effect, AMe ). In order to compensate for a possible increase of type I errors due to performing five comparisons (for HDT + 2, HDT + 30, HDT + 59, R + 2, R + 13) the Benjamini-Hochberg correction was applied to the results of the Wilcoxon tests. Declarations Authors Contributions MT, JM conceptualized the experiment; MT, JM, MB acquired the funding; MT, JM designed the experiment; JM, MT programmed the stimulus; MT collected the data; MT, JM, MB discussed and interpreted the data; MT performed the statistical analysis and wrote the first draft; MT, JM, MB revised the paper. Competing Interest The authors have no competing interests as defined by Nature Portfolio, or other interests that might be perceived to influence the results and/or discussion reported in this paper. Acknowledgements The authors thank M. Patrice Jegouzo for his technical help in designing the experimental setup. This work was supported by the Centre National des Etudes Spatiales (CNES) and the European Space Agency (ESA). This study contributes to the IdEx Université de Paris ANR-18-IDEX-0001. Funding This research was founded by the Centre National des Etudes Spatiales (CNES), the Centre National de la Recherche Scientifique (CNRS) and Université Paris Cité. Data availability Data will be made available on reasonable request to Mr. Michele Tagliabue ( [email protected] ). References Bernard-Espina, J., Dal Canto, D., Beraneck, M., McIntyre, J. & Tagliabue, M. How Tilting the Head Interferes With Eye-Hand Coordination: The Role of Gravity in Visuo-Proprioceptive, Cross-Modal Sensory Transformations. Front. Integr. Neurosci. 16, (2022). Andersen, R. A., Snyder, L. H., Li, C. S. & Stricanne, B. Coordinate transformations in the representation of spatial information. Curr Opin Neurobiol 3, 171–176 (1993). Cohen, Y. E. & Andersen, R. A. A common reference frame for movement plans in the posterior parietal cortex. Nat Rev Neurosci 3, 553–562 (2002). Soechting, J. F. & Flanders, M. Errors in pointing are due to approximations in sensorimotor transformations. J Neurophysiol 62, 595–608 (1989). Sabes, P. N. Sensory integration for reaching: models of optimality in the context of behavior and the underlying neural circuits. Prog Brain Res 191, 195–209 (2011). Tagliabue, M. & McIntyre, J. A modular theory of multisensory integration for motor control. Front Comput Neurosci 8, 1 (2014). Henriques, D. Y., Klier, E. M., Smith, M. A., Lowy, D. & Crawford, J. D. Gaze-centered remapping of remembered visual space in an open-loop pointing task. J Neurosci 18, 1583–1594 (1998). McIntyre, J., Stratta, F. & Lacquaniti, F. Viewer-centered frame of reference for pointing to memorized targets in three-dimensional space. J Neurophysiol 78, 1601–1618 (1997). McIntyre, J., Stratta, F. & Lacquaniti, F. Short-term memory for reaching to visual targets: psychophysical evidence for body-centered reference frames. J Neurosci 18, 8423–8435 (1998). McGuire, L. M. M. & Sabes, P. N. Sensory transformations and the use of multiple reference frames for reach planning. Nat Neurosci 12, 1056–1061 (2009). Tagliabue, M. & McIntyre, J. Necessity is the Mother of Invention: Reconstructing Missing Sensory Information in Multiple, Concurrent Reference Frames for Eye-Hand Coordination. J Neurosci 31, 1397–1409 (2011). Henriques, D. Y. P., Medendorp, W. P., Gielen, C. C. A. M. & Crawford, J. D. Geometric computations underlying eye-hand coordination: orientations of the two eyes and the head. Exp Brain Res 152, 70–78 (2003). Schlicht, E. J. & Schrater, P. R. Impact of coordinate transformation uncertainty on human sensorimotor control. J Neurophysiol 97, 4203–4214 (2007). Abedi Khoozani, P. & Blohm, G. Neck muscle spindle noise biases reaches in a multisensory integration task. J. Neurophysiol. 120, 893–909 (2018). Burns, J. K. & Blohm, G. Multi-sensory weights depend on contextual noise in reference frame transformations. Front Hum Neurosci 4, 221 (2010). Tagliabue, M., Arnoux, L. & McIntyre, J. Keep your head on straight: Facilitating sensori-motor transformations for eye-hand coordination. Neuroscience 248, 88–94 (2013). Paillard, J. Brain and Space. in (ed. J.Paillard) 461–481 (Oxford University Press, 1991). Adamopoulos, K., Koutsouris, D., Zaravinos, A. & Lambrou, G. I. Gravitational Influence on Human Living Systems and the Evolution of Species on Earth. Mol. Basel Switz . 26, (2021). McIntyre, J., Zago, M., Berthoz, A. & Lacquaniti, F. Does the brain model Newton’s laws? Nat Neurosci 4, 693–694 (2001). Arnoux, L. et al. The visual encoding of purely proprioceptive intermanual tasks is due to the need of transforming joint signals, not to their interhemispheric transfer. J. Neurophysiol. 118, 1598–1608 (2017). Tagliabue, M. & McIntyre, J. When Kinesthesia Becomes Visual: A Theoretical Justification for Executing Motor Tasks in Visual Space. PLoS ONE 8, e68438 (2013). Ernst, M. O. & Banks, M. S. Humans integrate visual and haptic information in a statistically optimal fashion. Nature 415, 429–433 (2002). Sober, S. J. & Sabes, P. N. Flexible strategies for sensory integration during motor planning. Nat Neurosci 8, 490–497 (2005). Ma, W. J., Beck, J. M., Latham, P. E. & Pouget, A. Bayesian inference with probabilistic population codes. Nat Neurosci 9, 1432–1438 (2006). Fetsch, C. R., Pouget, A., DeAngelis, G. C. & Angelaki, D. E. Neural correlates of reliability-based cue weighting during multisensory integration. Nat Neurosci 15, 146–154 (2012). Fetsch, C. R., DeAngelis, G. C. & Angelaki, D. E. Bridging the gap between theories of sensory cue integration and the physiology of multisensory neurons. Nat. Rev. Neurosci. 14, 429–442 (2013). Banker, L. A. et al. The effects of a spaceflight analog with elevated CO2 on sensorimotor adaptation. J. Neurophysiol. 125, 426–436 (2021). Koppelmans, V. et al. Exercise as potential countermeasure for the effects of 70 days of bed rest on cognitive and sensorimotor performance. Front. Syst. Neurosci. 9, (2015). Morfoisse, T. et al. Modality-independent effect of gravity in shaping the internal representation of 3D space for visual and haptic object perception. J. Neurosci. Off. J. Soc. Neurosci. 44, e2457202023 (2024). Carriot, J., Mackrous, I. & Cullen, K. E. Challenges to the Vestibular System in Space: How the Brain Responds and Adapts to Microgravity. Front. Neural Circuits 15, 760313 (2021). Mikellidou, K., Cicchini, G. M., Thompson, P. G. & Burr, D. C. The oblique effect is both allocentric and egocentric. J. Vis. 15, 24 (2015). Barnett-Cowan, M., Snow, J. C. & Culham, J. C. Contribution of Bodily and Gravitational Orientation Cues to Face and Letter Recognition. Multisensory Res. 28, 427–442 (2015). Marendaz, C., Stivalet, P., Barraclough, L. & Walkowiac, P. Effect of gravitational cues on visual search for orientation. J. Exp. Psychol. Hum. Percept. Perform. 19, 1266–1277 (1993). Gammeri, R. et al. Modulation of vestibular input by short-term head-down bed rest affects somatosensory perception: implications for space missions. Front. Neural Circuits 17, (2023). Guerraz, M., Poquin, D. & Ohlmann, T. The role of head-centric spatial reference with a static and kinetic visual disturbance. Percept Psychophys 60, 287–295 (1998). Guerraz, M., Luyat, M., Poquin, D. & Ohlmann, T. The role of neck afferents in subjective orientation in the visual and tactile sensory modalities. Acta Otolaryngol 120, 735–738 (2000). Guerraz, M., Caudron, S., Thomassin, N. & Blouin, J. Influence of head orientation on visually and memory-guided arm movements. Acta Psychol Amst 136, 390–398 (2011). Templeton, W. B. The role of gravitational cues in the judgement of visual orientation. Percept. Psychophys. 14, 451–457 (1973). Cheng, S. & Sabes, P. N. Calibration of Visually Guided Reaching Is Driven by Error-Corrective Learning and Internal Dynamics. J. Neurophysiol. 97, 3057–3069 (2007). Eggert, T., Henriques, D. Y. P., Hart, B. M. ’t & Straube, A. Modeling inter-trial variability of pointing movements during visuomotor adaptation. Biol. Cybern. 115, 59–86 (2021). Smith, M. A., Ghazizadeh, A. & Shadmehr, R. Interacting adaptive processes with different timescales underlie short-term motor learning. PLoS Biol 4, e179 (2006). Lee, J. K. et al. Head Down Tilt Bed Rest Plus Elevated CO2 as a Spaceflight Analog: Effects on Cognitive and Sensorimotor Performance. Front. Hum. Neurosci. 13, (2019). Harris, L. R., Jenkin, M. & Herpers, R. Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright. J. Vestib. Res. 32, 325–340 (2022). Ong, J., Lee, A. G. & Moss, H. E. Head-Down Tilt Bed Rest Studies as a Terrestrial Analog for Spaceflight Associated Neuro-Ocular Syndrome. Front. Neurol . 12, (2021). Bernauer, E. et al. Knee-joint proprioception during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. Aviat. Space Environ. Med. 65, 1110?1115 (1994). Kouzaki, M. et al. Effects of 20-day bed rest with and without strength training on postural sway during quiet standing. Acta Physiol. Oxf. Engl. 189, 279–292 (2007). Reschke, M. F. et al. Postural Reflexes, Balance Control, and Functional Mobility with Long-Duration Head-Down Bed Rest. Aviat. Space Environ. Med. 80, A45–A54 (2009). Yamanaka, K. et al. The effects of long-term bed rest on H-reflex and motor evoked potential in the human soleus muscle during standing. Neurosci. Lett. 266, 101–104 (1999). Belavý, D. L. et al. Differential atrophy of the lower-limb musculature during prolonged bed-rest. Eur. J. Appl. Physiol. 107, 489–499 (2009). Xiong, Z., Tian, Y., Wang, X., Wei, K. & Bi, Y. Gravity matters for the neural representations of action semantics. Cereb. Cortex 33, 6862–6871 (2023). Bernard-Espina, J., Beraneck, M., Maier, M. A. & Tagliabue, M. Multisensory Integration in Stroke Patients: A Theoretical Approach to Reinterpret Upper-Limb Proprioceptive Deficits and Visual Compensation. Front. Neurosci. 15, 319 (2021). Schoenmaekers, C. et al. Neural correlates of vestibular adaptation in cosmonauts after long duration spaceflight. NPJ Microgravity 11, 71 (2025). Stein, B. E., Stanford, T. R. & Rowland, B. A. Development of multisensory integration from the perspective of the individual neuron. Nat. Rev. Neurosci. 15, 520–535 (2014). McIntyre, J. & Lipshits, M. Central processes amplify and transform anisotropies of the visual system in a test of visual-haptic coordination. J Neurosci 28, 1246–1261 (2008). Additional Declarations No competing interests reported. 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Michele","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABK0lEQVRIie2Rv0oDQRCHRwb2mpG0F/yTJxBGhKQR8yq7CElzxYGNRYqAkGsk117wJfIGLizEJqClYpBLc9UVqUJAiS4XokHurC32Y1l2l/1mfjAADsd/BEEAhMVxT0vQAF6/uJF9SKsVLn7ARiG9VZAr+uwoxfLld7lS5STCLF3wObS9hyed9mYqrueMYe/tsNFHsShRmka0ThPuAFEQajnJ1OguYEwmV8QaMSlVSBwQGxsskFoKo8avQeudhCSGmikLVigf/AlUy62yNur+ZcpIa0k2GFYqwBrI72qtBraLT4z7A0mgqxTRrN/yJdFzDloNs7Nk2glxNLTBTIXyaDJ/dX1x7MXd+Xy1nB3FkRljuJTtRnRTqmyxY6GfKeDO/hde+ktxOBwOx4YvS3tgT9uOAUQAAAAASUVORK5CYII=","orcid":"","institution":"Université Paris Cité, CNRS UMR 8002","correspondingAuthor":true,"prefix":"","firstName":"Tagliabue","middleName":"","lastName":"Michele","suffix":""},{"id":545787873,"identity":"b3e08c40-2e5a-4510-a7de-9b04856be187","order_by":1,"name":"McIntyre Joseph","email":"","orcid":"","institution":"Université Paris Cité, CNRS UMR 8002","correspondingAuthor":false,"prefix":"","firstName":"McIntyre","middleName":"","lastName":"Joseph","suffix":""},{"id":545787874,"identity":"cfe7f3ca-c136-46e6-bc6b-7a8c8aca2762","order_by":2,"name":"Beraneck Mathieu","email":"","orcid":"","institution":"Université Paris Cité, CNRS UMR 8002","correspondingAuthor":false,"prefix":"","firstName":"Beraneck","middleName":"","lastName":"Mathieu","suffix":""}],"badges":[],"createdAt":"2025-10-23 21:08:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7935209/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7935209/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":96206249,"identity":"41d064dd-ed71-45b1-9b9d-927ada8013f2","added_by":"auto","created_at":"2025-11-18 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17:22:23","extension":"xml","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":185926,"visible":true,"origin":"","legend":"","description":"","filename":"afa35992b2cf440aa8470d70394c0b9f1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/1057711fe5eddeef12a6686a.xml"},{"id":96253228,"identity":"bb110629-7dce-4440-b2d5-96c849e081c0","added_by":"auto","created_at":"2025-11-19 07:42:11","extension":"html","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":202883,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/3c0b443180753a995f6bb9f7.html"},{"id":96206246,"identity":"a9b03180-6ebb-4d48-9863-187e727a2e84","added_by":"auto","created_at":"2025-11-18 17:22:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":253784,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA)\u003c/strong\u003eNormalized total deviation of the responses, ΔTDev, quantified as absolute distance between the average responses and the targets. \u003cstrong\u003eB) \u003c/strong\u003eNormalized Aubert-Muller effect, ΔAMe, corresponds to responses deviation in the same (positive values) or opposite (negative values) direction than the head tilt. \u003cstrong\u003eC)\u003c/strong\u003eNormalized response distortion, ΔDist, representing the over- or under- estimations (positive and negative values, respectively) of between-target distances. All three parameters are reported over the six experimental sessions for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. Given the importance of the sign for Dist and AMe interpretation, the grand mean of the BDC session has been added to the normalized values. For the Bedrest group the mean, and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively; for the Control group, by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p\u0026lt;0.05 and p\u0026lt;0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/e9bce58f264515472bf9766c.png"},{"id":96252873,"identity":"8d9de847-77ed-4295-9fed-4d7615de5fd7","added_by":"auto","created_at":"2025-11-19 07:41:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":241539,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA\u003c/strong\u003e) Normalized responses’ variability, ΔMSD, and \u003cstrong\u003eB\u003c/strong\u003e) Normalized weight associated to visual information, Δω\u003csub\u003eV\u003c/sub\u003e, are reported for all six experimental sessions, for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. For the Bedrest group the mean and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively. For Controls, the same parameters are represented by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p\u0026lt;0.05 and p\u0026lt;0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/bbf2e441037885265d0d5854.png"},{"id":96252461,"identity":"4a25f29b-947b-4a40-b475-d173f2639e51","added_by":"auto","created_at":"2025-11-19 07:40:58","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":757310,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA)\u003c/strong\u003e In both Seated (top) and Supine (bottom) postures, infrared markers’ supports (yellow structures) are used for real-time tracking of the subject movements. A virtual reality headset is used to control visual information provided to the subjects. A remote control held in the not moving hand allows the subject to validate responses. \u003cstrong\u003eB)\u003c/strong\u003e Tested sensory conditions: V-P, in the cross-modal Visuo-Proprioceptive task the subjects memorize the orientation of blue bars and reproduce it by correctly prono-supinating the hand without having visual cues about the hand roll; V-V, in the uni-modal Visual task the blue bars are reproduced by controlling with the buttons of the remote control the orientation of a virtual representation of the hand (the actual hand is kept next to the body); P-P, in the unimodal Proprioceptive task, the subjects acquire the target orientation by sensing the wrist prono-supination level that turns green the capsule representing the hand. No visual cues about the hand orientation are available during the response phase either. \u003cstrong\u003eC) \u003c/strong\u003eIn some of the trials of each sensory condition the subjects are requested to laterally tilt the head between the target acquisition and the response phase. To control the direction and the amplitude of the neck flection the halo placed around the subjects’ eyes turns from red to green when approaching the desired orientation. \u003cstrong\u003eD)\u003c/strong\u003e Temporal organization of the experimental sessions for the Bedrest and Control groups. The green area represents the 60 days during which the Bedrest group remained in the Head Down Tilt (HDT) position. This period was preceded by a Baseline Data Collection (BDC) phase and followed by a Recovery (R) period.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/7c27a4b4b410a88d87bb23fe.jpeg"},{"id":96206254,"identity":"3da3958b-b816-41f7-bbc6-46d0e4bc5d25","added_by":"auto","created_at":"2025-11-18 17:22:23","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":481896,"visible":true,"origin":"","legend":"\u003cp\u003eExample of individual responses and associated analyses. \u003cstrong\u003eA)\u003c/strong\u003e The responses with head-straight (HS) are interpolated with the straight (blue) line, which represents the subject average behavior. The subject precision is associated to the responses’ variability which is quantified as their dispersion around the regression line. The subject responses’ total deviation is quantified by computing the mean absolute distance (green area) between the targets line (black) and the responses' regression line. The angle between the two lines is used to quantify the response distortions. Subject responses in the trials with left and right neck flexions are represented in panels \u003cstrong\u003eB)\u003c/strong\u003e and \u003cstrong\u003eC)\u003c/strong\u003e. Lighter and darker colors correspond to the responses in trials with and without sensory conflict respectively. These examples show how the imperceptible rotation of the visual scene can result in a shift of responses and hence of the line interpolating them. The ratio between the responses’ shift (\u003cem\u003eΔq\u003c/em\u003e\u003csub\u003e\u003cem\u003er,Hi\u003c/em\u003e\u003c/sub\u003e) and the amplitude of the scene rotation (\u003cem\u003eΔq\u003c/em\u003e\u003csub\u003e\u003cem\u003et,Hi\u003c/em\u003e\u003c/sub\u003e) is used to quantify the importance given to visual cues.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/d8252dd44c01be97b796c9ec.jpeg"},{"id":104808602,"identity":"8f090d12-edfc-47f7-88f3-97e6f6ce9dd7","added_by":"auto","created_at":"2026-03-17 12:38:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2655600,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/4d28b935-7203-4ed6-b364-ec9e0a19239f.pdf"},{"id":96250565,"identity":"8dd009de-2530-4db7-a007-1a1cca2db32e","added_by":"auto","created_at":"2025-11-19 07:38:39","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":447000,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7935209/v1/9a9e032a4ec8ff36c6506511.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Adaptation of multisensory integration for visuo-manual coordination during 60 days of bedrest","fulltext":[{"header":"Introduction","content":"\u003cp\u003eWhen performing goal-oriented hand movement, like reaching to seize an object, the brain has to convert visual information about the object position and orientation into an arm and hand configuration to correctly grasp it. Because the visually-acquired target information is intrinsically encoded in a retinal reference frame and the arm configuration is mainly sensed through joint-referenced proprioceptive signals, cross-reference, visuo-proprioceptive, transformations are required \u003csup\u003e\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. The sensory processing underlying reaching tasks and the references frames in which the information is encoded has been thoroughly investigated in humans\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe distribution and pattern of reaching errors have been used to investigate how sensory information is encoded and transformed across multiple reference frames \u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Studies suggest that errors in cross-reference transformations significantly influence the relative weighting of concurrent internal movement representations \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. It was also shown that the noisiness of the cross-reference transformations, and thus their impact, can be modulated by factors such as horizontal eye and head movements \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e and by lateral head tilts \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn a recent study, where we investigated the short-term effects of a supine posture on visuo-manual tasks in terms of motor performances and sensory strategy, we showed a clear increase of movement errors and visual dependency, but only for tasks requiring visuo-proprioceptive transformations\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. This result indicates that the head-vertical misalignment, and hence the alteration of gravitational, probably utricular, sensory inputs, interferes with cross-reference re-encoding.\u003c/p\u003e\u003cp\u003eThe significance of gravity in cross-modal transformations was first theorized by Paillard (1991), who proposed that the reference frames involved in visually guided movements are 'organized around the invariant vertical orientation of gravity'. Given that gravity has been one of the most consistent environmental factors throughout the evolution of our species on Earth \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, it raises the question of whether the crucial role of utricular signals on eye-hand coordination stems from intrinsic properties of the human neural system shaped through evolution (phylogenetic origin), making them difficult to modify, or if it is a result of the brain\u0026rsquo;s lifelong adaptation to performing complex visuo-motor tasks with the head upright (ontogenetic origin). In the latter case, the observed preference for the vertical head posture may be more adaptable, although orbital visuo-manual coordination experiments showed that the gravitational \u0026lsquo;prior\u0026rsquo; keep affecting astronauts\u0026rsquo; performances for weeks\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTo examine whether the preference for the head-gravity alignment is driven by phylogenetic or ontogenetic factors, we conducted a 60-day bedrest study with participant placed in a 6\u0026deg; head-down-tilt (HDT). They completed visuo-manual tasks requiring cross-modal visuo-proprioceptive (V-P) transformations, as well as unimodal visual (V-V) and proprioceptive (P-P) tasks. Their performance was compared to a control group that did not undergo bedrest. If the previously observed effects of short-term head-gravity misalignment on the V-P task \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e are ontogenetic rather than phylogenetic, we would expect that, after an initial disruption, bedrest participants would adapt to the HDT posture, gradually approaching the performance level of the control group.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eAll participants successfully performed all experimental sessions, except for one control subject, who had to withdraw from the protocol for non-study-related reasons.\u003c/p\u003e\u003cp\u003eThe results from the baseline data collection (BDC), which occurred seven days before the onset of the HDT bedrest, were consistent with the observations of previous studies using a similar experimental paradigm\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Despite considerable inter-individual variability, parameters such as accuracy, precision, and visuo-dependency were consistently modulated by the sensory condition (see Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Furthermore, correlations across subsequent experimental sessions (see Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e) indicate that inter-individual differences tended to persist over time, supporting both the robustness of the present experimental paradigm and the reliability of the data analyses. To account for this initial variability and isolate the effect of HDT exposure, all individual parameters measured during HDT and recovery (R) were normalized by subtracting each subject\u0026rsquo;s BDC value. In the following sections, we present the normalized results for accuracy, reflecting participants\u0026rsquo; ability to correctly perform the task; for precision, indicating the reproducibility and robustness of their performance; and for visual-weight, describing the sensory strategy they used to achieve the task. For each of these parameters we present the results for the cross-modal (V-P) task and then for the two unimodal tasks (V-V and P-P).\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAccuracy\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eFigure 1A shows the normalized total deviation (\u003cem\u003eΔTDev\u003c/em\u003e) of responses for both the \u003cem\u003eControl\u003c/em\u003e and \u003cem\u003eBedrest\u003c/em\u003e groups across all experimental sessions: BDC-7 (7 days before the start of bedrest); HDT\u0026thinsp;+\u0026thinsp;2, HDT\u0026thinsp;+\u0026thinsp;30 and HDT\u0026thinsp;+\u0026thinsp;59 (2, 30, and 59 days after the start of bedrest); and R\u0026thinsp;+\u0026thinsp;2 and R\u0026thinsp;+\u0026thinsp;13 (2 and 13 days after the beginning of recovery).\u003c/p\u003e\u003cp\u003eIn the cross-modal V-P task (top plot), \u003cem\u003eControl\u003c/em\u003e participants (shaded grey) who repeated the task in an upright position, exhibited a gradual reduction in total deviation across all sessions, suggesting a learning effect. In contrast, the \u003cem\u003eBedrest\u003c/em\u003e group showed a different pattern: at the first session following the onset of head-down tilt (HDT\u0026thinsp;+\u0026thinsp;2), their total deviation increased markedly, reflecting an initial perturbation caused by the new head/body orientation. This was followed by a progressive improvement in accuracy over subsequent sessions. As a result, a significant group difference emerged at HDT\u0026thinsp;+\u0026thinsp;2, but this difference was no longer significant at later sessions (see statistics in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), suggesting that bedrest participants partially adapted to the HDT. However, although \u003cem\u003eΔTDev\u003c/em\u003e values of the two groups at HDT\u0026thinsp;+\u0026thinsp;30 and HDT\u0026thinsp;+\u0026thinsp;59 were no longer statistically different, the \u003cem\u003eBedrest\u003c/em\u003e group\u0026rsquo;s accuracy did not fully reach the \u003cem\u003eControl\u003c/em\u003e level, suggesting that their adaptation was incomplete. Even during the 13-day recovery (R) period, the accuracy of the two groups did not completely converge, suggesting a lasting after-effect of the 60-day HDT, which was not fully compensated even after two weeks in an upright posture.\u003c/p\u003e\u003cp\u003eChanges in accuracy (TDev) can be ascribed to two main factors: the Aubert-Muller effect (\u003cem\u003eAMe\u003c/em\u003e; Fig.\u0026nbsp;1B), a global shift of the responses toward/away from the direction of the lateral head-tilt; and orientation distortion (\u003cem\u003eDist\u003c/em\u003e; Fig.\u0026nbsp;1C), defined as the over/under estimation of the angular distance between targets. Figure\u0026nbsp;1B-C and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e suggest that the \u003cem\u003eΔTDev\u003c/em\u003e differences between Bedrest and Control groups at HDT\u0026thinsp;+\u0026thinsp;2 in the V-P task were more related to \u003cem\u003eΔAMe\u003c/em\u003e than to \u003cem\u003eΔDist\u003c/em\u003e. Indeed, significant differences between the two groups were observed for \u003cem\u003eΔAMe\u003c/em\u003e at HDT\u0026thinsp;+\u0026thinsp;2 and HDT\u0026thinsp;+\u0026thinsp;30, but not for the response contraction (negative \u003cem\u003eΔDist\u003c/em\u003e). The between group difference in \u003cem\u003eΔAMe\u003c/em\u003e indicates that, while the Control group quickly learned to reduce to zero the initial (BDC-7) deviation of the responses toward the direction of the head tilt, in the \u003cem\u003eBedrest\u003c/em\u003e group the HDT posture initially amplified this deviation. Over the following two months, however, \u003cem\u003eΔAMe\u003c/em\u003e gradually decreased, reaching levels comparable to those of the \u003cem\u003eControl\u003c/em\u003e group in the last 3 sessions. This observation provides the clearest evidence for gradual adaptation to HDT. \u003cem\u003eDist\u003c/em\u003e, however, followed similar patterns in both bedrest participants and controls, with both groups showing an initial contraction of responses with respect to the target spacing, followed by a similar reduction of this distortion toward zero for later sessions, though with slightly different dynamics. The combination of these two effects can explain the inter-group differences in \u003cem\u003eΔTDev\u003c/em\u003e shown in Fig.\u0026nbsp;1A. Both HDT and Control participants reduced the contraction effect with practice, resulting in a gradual decrease in \u003cem\u003eΔTDev\u003c/em\u003e for both groups, but the bedrest participants had a higher \u003cem\u003eΔTDev\u003c/em\u003e due to the \u003cem\u003eΔAMe\u003c/em\u003e induced by the HDT. The fact that bedrest participants gradually decreased both \u003cem\u003eΔAMe\u003c/em\u003e and \u003cem\u003eΔDist\u003c/em\u003e means that their \u003cem\u003eΔTDev\u003c/em\u003e diminishes more quickly than for controls, resulting in a gradual reduction in the inter-group difference for \u003cem\u003eΔTDev.\u003c/em\u003e\u003c/p\u003e\u003cp\u003eUnlike in the cross-modal task, in the two unimodal conditions (V-V and P-P; middle and bottom plots), \u003cem\u003eΔTDev\u003c/em\u003e showed neither clear fluctuations over time nor significant differences between groups, even at HDT\u0026thinsp;+\u0026thinsp;2. Similarly, HDT does not significantly modulate \u003cem\u003eΔAMe\u003c/em\u003e and \u003cem\u003eΔDist\u003c/em\u003e in the unimodal tasks (V-V and P-P). The acute effect of HDT on the V-P task, but not on the V-V and P-P tasks, suggests that HDT specifically interfered with participants\u0026rsquo; ability to perform cross-modal transformations rather than with their general ability to use visual and proprioceptive information, and it supports the notion that the utilization of gravity-related signals to stabilize motor performance is a mechanism mainly engaged in cross-modal tasks. Moreover, the lack of correlation between individual modulations of accuracy parameters (\u003cem\u003eΔTDev, ΔAMe and ΔDist\u003c/em\u003e) at HDT\u0026thinsp;+\u0026thinsp;2 in the cross-modal task and in the two unimodal tasks (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) rejects the hypothesis of a link between the acute decrease in response accuracy in the V-P condition and the smaller decreases of visual and proprioceptive accuracy per se. Similarly, the gradual reduction of the between-group difference during the two-month HDT period for the V-P task, but not for the unimodal tasks, together with the lack of correlation between the session-to-session changes in the V-P and both V-V and P-P unimodal tasks (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), suggests that HDT adaptation and the post-effect during recovery specifically involved the ability to perform cross-modal transformations.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFigure 1. \u003cb\u003eA)\u003c/b\u003e Normalized total deviation of the responses, \u003cem\u003eΔTDev\u003c/em\u003e, quantified as absolute distance between the average responses and the targets. \u003cb\u003eB)\u003c/b\u003e Normalized Aubert-Muller effect, \u003cem\u003eΔAMe\u003c/em\u003e, corresponds to responses deviation in the same (positive values) or opposite (negative values) direction than the head tilt. \u003cb\u003eC)\u003c/b\u003e Normalized response distortion, \u003cem\u003eΔDist\u003c/em\u003e, representing the over- or under- estimations (positive and negative values, respectively) of between-target distances. All three parameters are reported over the six experimental sessions for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. Given the importance of the sign for \u003cem\u003eDist\u003c/em\u003e and \u003cem\u003eAMe\u003c/em\u003e interpretation, the grand mean of the BDC session has been added to the normalized values. For the Bedrest group the mean, and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively; for the Control group, by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 and p\u0026thinsp;\u0026lt;\u0026thinsp;0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eComparing Bedrest and Control groups for each experimental session (HDT\u0026thinsp;+\u0026thinsp;2, +\u0026thinsp;30, +59 and R\u0026thinsp;+\u0026thinsp;2, R\u0026thinsp;+\u0026thinsp;13) and for each sensory condition (V-P, V-V and P-P). Bolded values correspond to significant Bedrest-Control differences after Benjamini-Hochberg corrections of the t-test results.\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"12\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;30\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;59\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c12\" namest=\"c11\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;13\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003et\u003c/em\u003e(32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003et\u003c/em\u003e(32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003et\u003c/em\u003e(32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003et\u003c/em\u003e(32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003et\u003c/em\u003e(32)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\u003cp\u003e\u003cem\u003eV-P\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔTDev\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.0029\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.0971\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.0493\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.1062\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e0.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.1720\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔDist\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.0177\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.1814\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.2881\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-1.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.8686\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.6871\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔAMe\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.0013\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.0132\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.1129\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.2876\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e0.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.2766\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔMSD\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.0014\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.0067\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e\u003cb\u003e0.0135\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e\u003cb\u003e0.0129\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e2.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e\u003cb\u003e0.0186\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003e0.0013\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u003cb\u003e0.0004\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e\u003cb\u003e0.0021\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e\u003cb\u003e0.0259\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.0875\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\u003cp\u003e\u003cem\u003eV-V\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔTDev\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.4203\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.7820\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-0.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.7681\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.2671\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.1241\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔDist\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.4843\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.7496\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.9062\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.7308\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.1311\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔAMe\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-1.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.8418\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.7128\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.6610\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-1.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.9418\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-1.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.9353\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔMSD\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.3776\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.1019\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.2259\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.0778\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e2.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.0127\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-0.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.7368\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-1.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.9726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-1.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.9723\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-1.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.9461\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-2.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.9820\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\u003cp\u003e\u003cem\u003eP-P\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔTDev\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.2056\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.2086\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.1197\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.1644\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.1295\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔDist\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.2890\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.1563\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.2533\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.3753\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.5104\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔAMe\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.1396\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.5488\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.2605\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-1.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.8880\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-0.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.6905\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔMSD\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.1414\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.0246\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.0255\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.0380\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.1030\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.4284\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-1.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.8642\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.8171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-1.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.9693\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-1.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.9591\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eFor each pair of consecutive sessions, the table reports correlations between session-to-session changes in the visuo-proprioceptive (V\u0026ndash;P) and unimodal (V\u0026ndash;V, P\u0026ndash;P) conditions for total deviation (TDev), Aubert\u0026ndash;Muller effects (AMe), and response distortion (Dist). Bolded values correspond to significant correlations after Benjamini-Hochberg corrections (performed for each variable separately): none of the correlation is statistically significant.\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"14\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003e\u003cem\u003eΔTDev\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c10\" namest=\"c7\"\u003e\u003cp\u003e\u003cem\u003eΔAMe\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c14\" namest=\"c11\"\u003e\u003cp\u003e\u003cem\u003eΔDist\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003eV-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c10\" namest=\"c7\"\u003e\u003cp\u003eV-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c14\" namest=\"c11\"\u003e\u003cp\u003eV-P\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eBedrest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eBedrest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c12\" namest=\"c11\"\u003e\u003cp\u003eBedrest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c14\" namest=\"c13\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;2 - BDC-7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.03\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.21\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.57\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.40\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e0.08\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e-0.35\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.22\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.40\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.19\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.43\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e0.32\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e-0.46\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e-0.11\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;30 -HDT\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.13\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.09\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.04\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e0.14\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.03\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.91\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.16\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.23\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e0.06\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e-0.30\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.38\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;59 - HDT\u0026thinsp;+\u0026thinsp;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.08\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.22\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e0.06\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e-0.16\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.54\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.39\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.59\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.11\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e0.08\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e0.26\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.07\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.79\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;2 - HDT\u0026thinsp;+\u0026thinsp;59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.06\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.14\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.08\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e-0.34\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e-0.16\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.58\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.35\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.42\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e0.12\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.13\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;13 - HDT\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.02\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.02\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.23\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.12\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e-0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.12\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.28\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.26\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e\u003cem\u003e0.15\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e\u003cem\u003e0.09\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003ePrecision\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe normalized individual response variability (\u003cem\u003eΔMSD\u003c/em\u003e) showed very different time courses for the \u003cem\u003eBedrest\u003c/em\u003e and \u003cem\u003eControl\u003c/em\u003e groups in the cross-modal V-P task. Figure\u0026nbsp;2A shows a clear MSD decrease between BDC-7 and HDT\u0026thinsp;+\u0026thinsp;2 for \u003cem\u003eControl\u003c/em\u003e participants. This decrease aligns with the results of our previous studies, where participants were consecutively tested in two different experimental conditions\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e: in those studies, once the main effect of the experimental manipulation was subtracted, the condition performed second was consistently associated with lower response variability than the first one, independent of the specific condition. This clear reduction in variability between the first two experimental sessions was unlikely to result from an improved ability to perform cross-modal transformations: statistical theories of multisensory integration, such as the Maximum Likelihood Principle (MLP)\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, would predict that a reduction of the noise associated to cross-modal sensory transformations should directly result in an increase of the visual sensory weighting. However, the present increase in precision in Controls is not accompanied by a clear change in sensory strategy (see visual weight, \u003cem\u003eΔω\u003c/em\u003e\u003csub\u003eV\u003c/sub\u003e, in Fig.\u0026nbsp;2B), nor is there a significant correlation between the individual modulations of precision and changes in visual weighting (R\u0026thinsp;=\u0026thinsp;0.43, p\u0026thinsp;=\u0026thinsp;0.12). Instead, as in our previous studies, this reduction in response variability among Controls is more likely explained by increased familiarity with the task/procedure and by motor learning, driven by the occasional feedback provided to sustain participants' motivation. After this initial MSD decrease, the \u003cem\u003eControl\u003c/em\u003e group\u0026rsquo;s response variability remains quite stable, with only an additional small decrease when two experimental sessions are conducted in close succession (3 days apart between HDT\u0026thinsp;+\u0026thinsp;59 and R\u0026thinsp;+\u0026thinsp;2).\u003c/p\u003e\u003cp\u003eIn contrast to the \u003cem\u003eControl\u003c/em\u003e group, the \u003cem\u003eBedrest\u003c/em\u003e group showed no decrease in variability between BDC-7 and HDT\u0026thinsp;+\u0026thinsp;2; instead, they exhibited a slight increase. This pattern suggests that the HDT condition either masked or interfered with the early learning effect observed in Controls. Moreover, the significant correlation between individual \u003cem\u003eΔMSD\u003c/em\u003e and \u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e at HDT\u0026thinsp;+\u0026thinsp;2 (R = -0.48, p\u0026thinsp;=\u0026thinsp;0.03) supports the idea that misalignment of the head with gravity affects cross-modal processing precision: as mentioned above, statistical theories based on the Maximum Likelihood Principle (MLP) predict that changes in cross-modal transformation noise should directly influence sensory weighting. The implications of this between-group difference will be addressed in more detail in the discussion, in light of previous findings.\u003c/p\u003e\u003cp\u003eDuring the two months of HDT the \u003cem\u003eBedrest\u003c/em\u003e group showed a fairly stable response variability. Even at the transition from the HDT to recovery (R) phase, only a small decrease in variability, similar to that of the Control group, was observed. This \u0026minus;\u0026thinsp;10.5\u0026deg;\u003csup\u003e2\u003c/sup\u003e drop appears considerably smaller than the \u0026minus;\u0026thinsp;44\u0026deg;\u003csup\u003e2\u003c/sup\u003e decrease observed in our previous short-term experiment for the participants who performed the task first in the supine and then in the seated condition\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. The smaller amplitude here may be a consequence of the longer duration of body-gravity misalignment, which could lead to lasting interference in the participants\u0026rsquo; ability to perform cross-modal transformations, that persisted after returning to the seated position during recovery.\u003c/p\u003e\u003cp\u003eAlthough the \u003cem\u003eΔMSD\u003c/em\u003e of the \u003cem\u003eBedrest\u003c/em\u003e group considered alone did not appear to undergo large modulations, comparing it to the \u003cem\u003eControls\u003c/em\u003e showed strong between-group differences: the difference in the MSD modulations between BDC-7 and HDT\u0026thinsp;+\u0026thinsp;2 for Bedrest and Control participants resulted in a significant group difference at HDT\u0026thinsp;+\u0026thinsp;2 (see Fig.\u0026nbsp;2A and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This significant difference persisted, though to a lesser extent, at HDT\u0026thinsp;+\u0026thinsp;30 and at HDT\u0026thinsp;+\u0026thinsp;59, and even during the recovery period (R\u0026thinsp;+\u0026thinsp;2 and R\u0026thinsp;+\u0026thinsp;13). The persistence of the significant Bedrest-Control difference during the Recovery phase reinforces the idea that the 60-day HDT resulted in a significant after-effect on participants\u0026rsquo; precision.\u003c/p\u003e\u003cp\u003eConsistent with our previous study showing no acute effect of the supine posture on the unimodal tasks precision\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, no significant difference between \u003cem\u003eBedrest\u003c/em\u003e and \u003cem\u003eControl\u003c/em\u003e participants was observed at HDT\u0026thinsp;+\u0026thinsp;2 in \u003cem\u003eΔ\u003c/em\u003eMSD for either unimodal tasks (V-V and P-P). This lack of difference persisted for the whole duration of the experiment. Because in \u003cb\u003eFig.\u0026nbsp;2A\u003c/b\u003e the pattern of the average \u003cem\u003eΔMSD\u003c/em\u003e in the unimodal task appears qualitatively similar to that in the cross-modal task (especially for the \u003cem\u003eControl\u003c/em\u003e group), we tested for possible correlations between individual session-to-session changes in \u003cem\u003eMSD\u003c/em\u003e in the cross-modal and unimodal tasks, to further examine the hypothesis that the modulations of response variability in the V-P condition could be due to smaller, non-detectable, variations of visual and proprioceptive precision. The lack of significant correlations (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) does not support this hypothesis.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eSensory strategy (visual weighting)\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe difference between the \u003cem\u003eBedrest\u003c/em\u003e and \u003cem\u003eControl\u003c/em\u003e groups in the cross-modal V-P task is even more striking in terms of sensory weighting (Fig.\u0026nbsp;2B). Consistent with our previous short-term study\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, which demonstrated a greater visual dependency in the supine than in the seated position, at HDT\u0026thinsp;+\u0026thinsp;2 the visual weight (ω\u003csub\u003eV\u003c/sub\u003e) increased substantially for the \u003cem\u003eBedrest\u003c/em\u003e but not for the \u003cem\u003eControl\u003c/em\u003e participants, resulting in a significant difference between the two groups. Surprisingly, the difference between the two groups did not decrease during the two months of HDT, and even after resuming the seated posture (R\u0026thinsp;+\u0026thinsp;2), the difference remained significant with only a slight reduction. After thirteen days of recovery, the difference between the two groups was still visible but no longer significant. As for the response precision and, to a lesser extent, accuracy, the persistence of a difference in visual dependency between the two groups during the Recovery period appears to be a post-effect of the two-month bedrest, suggesting that, despite the lack of change of the visual dependency during the HDT phase, the participants have adapted to the tilted posture and were unable to quickly switch back to their baseline (BDC) sensory strategy.\u003c/p\u003e\u003cp\u003eAs with all previously reported parameters, the results were very different for the unimodal tasks: for both V-V and P-P tasks, the visual weight measured for the Bedrest group showed only small variations over time and is never significantly larger than that of Controls (Fig.\u0026nbsp;2B, middle and lower panels). It is interesting to notice however, that in both unimodal conditions the visual weight of the Control group showed a qualitative tendency to increase over time. This could be due to de fact that in all sensory conditions the feedback about their responses seldomly provided to the participants to keep them motivated was visual. This might have gradually biased them toward a visual strategy.\u003c/p\u003e\u003cp\u003eTo determine whether the visual dependency changes in the V-P condition relate to the sensory strategy in the unimodal tasks, correlations between cross-modal and unimodal results are reported in the right part of Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The increase in visual weight for the \u003cem\u003eBedrest\u003c/em\u003e group between BDC-7 and HDT\u0026thinsp;+\u0026thinsp;2 in the V-P condition appears unrelated to the \u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e in the unimodal tasks. These results suggest that the strong increase in visual dependency in the cross-modal condition is not due to some combination of the smaller, non-significant, \u003cem\u003eω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e increases in the V-V and P-P unimodal conditions. This interpretation is supported by the fact that, for Control participant as well, the individual \u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e values in the V-P task are not correlated with those in the P-P condition, and are even negatively correlated with those in the V-V condition.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFigure 2. A\u003c/b\u003e) Normalized responses\u0026rsquo; variability, \u003cem\u003eΔMSD\u003c/em\u003e, and \u003cb\u003eB\u003c/b\u003e) Normalized weight associated to visual information, \u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e, are reported for all six experimental sessions, for both Bedrest and Control groups and for the three sensory conditions: cross-modal visuo-proprioceptive (V-P), uni-modal visual (V-V) and uni-modal proprioceptive (P-P). The normalized value for the BDC (brown dot) is reported to provide a clear cue about its temporality and the acute effect of the HDT. For the Bedrest group the mean and the 95% confidence interval values are represented by a circle and the vertical whiskers, respectively. For Controls, the same parameters are represented by a square and the width of the surrounding shaded area. * and ** represent statistical significance (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 and p\u0026thinsp;\u0026lt;\u0026thinsp;0.01 respectively) of the t-tests between Bedrest and Control groups, with Benjamini-Hochberg correction.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eFor each pair of consecutive sessions, the table reports correlations between session-to-session changes in the visuo-proprioceptive (V\u0026ndash;P) and unimodal (V\u0026ndash;V, P\u0026ndash;P) conditions for response variability (MSD) and\u003c/em\u003e for the \u003cem\u003evisual weight (ω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e). Bolded values correspond to significant correlations after Benjamini-Hochberg corrections (performed for each variable separately): none of the correlation is statistically significant.\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"10\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" morerows=\"3\" nameend=\"c2\" namest=\"c1\" rowspan=\"4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003e\u003cem\u003eΔMSD\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c10\" namest=\"c7\"\u003e\u003cp\u003e\u003cem\u003eΔω\u003c/em\u003e\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003eV-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c10\" namest=\"c7\"\u003e\u003cp\u003eV-P\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eBedrest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eBedrest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;2 - BDC-7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.11\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.06\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.59\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.52\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.07\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.16\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.24\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;30 -\u003c/p\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.23\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.15\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.33\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.43\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;59 -\u003c/p\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.07\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.04\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.14\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.30\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.14\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.41\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.02\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.26\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;2 -\u003c/p\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.52\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e0.40\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.11\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.86\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.11\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.10\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e0.22\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.04\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.88\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eR\u0026thinsp;+\u0026thinsp;13 -\u003c/p\u003e\u003cp\u003eHDT\u0026thinsp;+\u0026thinsp;2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eV-V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e0.14\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.45\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.18\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.45\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eP-P\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003e-0.17\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003e-0.20\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003e-0.04\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003e-0.05\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study investigated the effects on eye-hand coordination of 60 days of head-down tilt (HDT) bedrest, a space-analog, and focused on the brain\u0026rsquo;s ability to adapt to altered gravitational inputs. Our results can be interpreted across three main phases: the acute effect of HDT at its onset, participants\u0026rsquo; adaptation during the two-month bedrest period, and the post-effects observed during recovery. Comparing the cross-modal visuo-proprioceptive (V-P) task with the unimodal tasks (V-V and P-P) allowed us to better discriminate changes in cross-modal sensory transformations from those affecting visual or proprioceptive processing alone.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAcute effect of HDT\u003c/b\u003e: at the beginning of HDT (HDT\u0026thinsp;+\u0026thinsp;2), participants showed a deterioration in performance on the V-P task, primarily as an increase in response error (accuracy loss), whereas control participants tested in the seated position did not lose accuracy and improved their precision. This acute effect replicates and extends our earlier finding that supine posture perturbs cross-modal transformations\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Interestingly, the increase in variability of the responses for bedrest participants\u0026rsquo; (\u003cem\u003eΔMSD\u0026thinsp;=\u003c/em\u003e\u0026thinsp;2.4\u0026deg;\u003csup\u003e2\u003c/sup\u003e) was however much smaller than the 26\u0026deg;\u003csup\u003e2\u003c/sup\u003e increase previously observed when considering only the subjects tested seated and then supine in the same day\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. We interpret this difference as the result of two competing processes: a reduction in response variability due to task familiarization (clearly visible in the Control group), and a perturbation of cross-modal sensory transformations due to altered otolithic signals when supine. Consistent with this interpretation, in our previous short-term experiment the variability modulation was even larger (43\u0026deg;\u003csup\u003e2\u003c/sup\u003e) for the participants tested supine and then seated and for which familiarization and posture effects sum up.\u003c/p\u003e\u003cp\u003eCompared to our previous short-term study, participants in the present study had more time to familiarize themselves with the task completing all three experimental conditions (V-P, V-V and P-P) before the start of bedrest, which may have favored the reduction in procedural variability, and thus the almost full compensation of the posture effect.\u003c/p\u003e\u003cp\u003eAn alternative explanation for the attenuated posture effect on response precision is that HDT could have suppressed session-to-session learning, as a previous bedrest study suggested\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. However, this interpretation is not supported by the concurrent accuracy deterioration observed here and the fact that participants in our previous short-term study\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e still displayed robust posture effects even when tested in the seated and then supine conditions.\u003c/p\u003e\u003cp\u003eIn the light of these results and considerations, the acute worsening of the \u003cem\u003eBedrest\u003c/em\u003e group\u0026rsquo;s performance with respect to the \u003cem\u003eControl\u003c/em\u003e group in the V-P task likely arises from a postural effect rather than a general inhibition of motor learning. This interpretation is also consistent with findings from other visuo-manual coordination tasks, such as the Purdue Pegboard Test (PTT) during bedrest\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, where posture selectively affected PPT execution time but not mental rotation performance, suggesting a specific impact on visuo-manual control rather than spatial representation more generally, in line with the lack of effect of the supine posture on the perception of visual and haptic objects\u0026rsquo; dimensions\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe acute degradation in V-P performance of the Bedrest group with respect to the \u003cem\u003eControl\u003c/em\u003e group, was also accompanied by a significant increase in visual dependency (ω\u003csub\u003eV\u003c/sub\u003e), indicating a clear change in multisensory strategy. This shift aligns with our previous findings\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and supports broader evidence for sensory reweighting as a mechanism of adaptation to altered gravitational contexts\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Unlike the cross-modal task, the unimodal tasks (V-V and P-P) were largely unaffected by posture both in terms of response errors and sensory strategy, highlighting that the observed deficits were specific to the ability to perform visuo-proprioceptive transformations.\u003c/p\u003e\u003cp\u003eThe absence of acute effect of posture in the V-V task is in line with results from a comparable orientation reproduction test study\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. We note however that supine posture was reported to affect other visual tasks, such as letters identification and face recognition\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eOn the other hand, the results from the P-P task appear in contradiction with the underestimation of somatosensory stimulations reported in the only previous attempts, to our knowledge, to investigate upper-limb proprioception during HDT\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. A possible explanation for this apparent contradiction could reside in the fact that in this previous study proprioception was assessed via electrical stimulation on passive subjects, whereas our paradigm required active movements of the arm, which may be less sensitive to postural changes due to increased muscle tone enhancing proprioceptive input.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAdaptation during 60 days bedrest\u003c/strong\u003e\u003cp\u003eThe longitudinal measurements obtained in this study provide a unique view of behavioral adaptation during prolonged HDT. Over the two-month bedrest, participants\u0026rsquo; performance gradually improved, reducing the accuracy gap with controls. This recovery was primarily driven by a gradual reduction of the Aubert effect\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e - the systematic deviation of responses toward the direction of lateral head tilt - which was most pronounced during the first HDT session. This pattern suggests that the initial performance decline resulted from the inability to use gravity as an external reference for motor stabilization and that participants gradually learned to compensate for this loss. Similar roll-tilt-induced response deviations have been reported for subjective visual and tactile vertical tasks, as well as in visuo-manual reproduction tasks\u003csup\u003e\u003cspan additionalcitationids=\"CR37\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, but to our knowledge, this is the first study to track their progressive reduction over a long-duration bedrest.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eIn contrast to accuracy, participants\u0026rsquo; precision did not show significant improvement during HDT. This dissociation between the time courses of constant (accuracy) and variable (precision) error components resembles the gradual visuo-motor learning process described in the literature, where accuracy improves faster than precision\u003csup\u003e\u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. The fact that accuracy improvements were observed for the cross-modal V-P task, but not for unimodal tasks, indicates that, similarly to the acute effect, this learning specifically involved the re-encoding of sensory information across modalities, rather than general visual or proprioceptive performance.\u003c/p\u003e\u003cp\u003eDespite the observed adaptation, participants never fully matched the accuracy or precision of controls, even after two months of HDT. This may indicate that a longer period of exposure would be needed to achieve complete compensation, or that certain aspects of visuo-proprioceptive transformations cannot fully recover in the absence of gravitational reference frames. This interpretation is consistent with theoretical work suggesting that referencing sensory information to gravity provides an optimal solution for cross-modal integration\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e and that its absence would lead to an unavoidable degradation in performance.\u003c/p\u003e\u003cp\u003eInterestingly, visual dependency did not decrease during the HDT period despite the observed improvement in accuracy, and remained elevated until after the recovery period. This observation is in line with the results of classical \u0026lsquo;rod and frame\u0026rsquo; test showing no significant evolutions during bedrest\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e and with the predictions from our concurrent model of multisensory integration, based on maximum likelihood principles\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, which forecasts no change in visual weighting even if cross-modal transformation noise improves (see Supplementary Information). Thus, the persistent visual dependency should not be interpreted as a failure to adapt, but it rather represents an optimal sensory strategy.\u003c/p\u003e\u003cp\u003eThe performance of bedrest participants in the unimodal tasks (V-V and P-P) showed only small, non-significant changes throughout the HDT phase and did not differ from controls. Our observations for the V-V condition appear in line with a previous study showing no clear effects of bedrest on visual perceptual tasks other than a decrease in reliance on external visual cues\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. This latter finding recalls the slight (non-significant) visual weight increase and decrease observed here for control and bedrest subjects, respectively. The lack of degradation of either precision or accuracy in the V-V tasks also suggests that, although the Spaceflight Associated Neuro-Ocular Syndrome (SANS) is a known potential side effect of bedrest\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e (two of the 20 participants developed SANS during the protocol), performance in the present orientation reproduction tasks were apparently not affected by possible degradations of the visual system.\u003c/p\u003e\u003cp\u003eOur results from the P-P task, suggesting that upper-body proprioception is preserved during the two months bedrest, represent a novel dataset and it can hardly be compared to any previous results in the literature, which focused on the lower-limbs and showed a significant degradation of proprioception\u003csup\u003e\u003cspan additionalcitationids=\"CR46 CR47\" citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. This difference likely relates to the fact that even during HDT, the arms continue to be used in a normal manner. Indeed, during bedrest only lower-limbs muscles face significant atrophy\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. Interestingly, this arm-leg difference is also reflected in the semantic processing of verbs referring to lower- and upper-limb actions, with a specific effect on the semantic representation of lower-limbs actions following HDT\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eRecovery\u003c/strong\u003e\u003cp\u003eParticipants continued to display reduced precision and slightly lower accuracy relative to controls, even after returning to an upright posture. Visual dependency also remained higher than in controls for several days. These findings indicate that the adaptation to HDT persisted into recovery, consistent with prior observations using the rod-and-frame test\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. One interpretation is that participants not only learned to down-weight gravity cues during HDT but also partially \u0026ldquo;unlearned\u0026rdquo; how to exploit them once they became available again, leading to suboptimal behavior relative to controls who never experienced prolonged tilt. This result suggests that the human preference for an upright posture during visuo-motor tasks is highly flexible and can be temporarily overwritten by experience.\u003c/p\u003e\u003c/p\u003e\u003cp\u003eThis apparent interference between the ability to perform transformations with and without gravitational cues aligns with the hypothesis that visuo-proprioceptive transformations are supported by recurrent neural networks in the intraparietal sulcus (IPS), which receive convergent visual, somatosensory, and vestibular inputs\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e. Prolonged HDT may induce gradual modification of the IPS synaptic connections to adapt to the altered otolithic input, similar to the functional neural connectivity changes reported in cosmonauts post-flight\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Consequently, during recovery the cross-modal transformations must rely on newly modified neural networks that are no longer optimized to the upright posture.\u003c/p\u003e\u003cp\u003eIn conclusion, the adaptation observed during the two-month bedrest and its subsequent effects on participants' precision and multisensory integration during the recovery period strongly support the notion that the human preference for head postures aligned with gravity during visuo-motor tasks\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e is primarily ontogenetic rather than phylogenetic, in line with animal model data showing that multisensory integration skills are not innate, but they emerge from cross-modal experiences in a specific environment\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. In other words, this preference does not appear to be a 'hard-wired' evolutionary trait but rather the result of individual adaptation to Earth's gravitational environment, where gravity-related signals are used to enhance visuo-motor coordination. This finding has significant implications for space and planetary exploration, as well as clinical applications. It suggests that astronauts\u0026rsquo; brains may adapt to weightlessness in ways that could hinder their visuo-manual coordination upon re-exposure to gravity, and it offers hope for rehabilitation of patients with vestibular dysfunction by highlighting the brain\u0026rsquo;s capacity to recalibrate sensory integration strategies. However, the observed persistence of differences with control subjects toward the end of bedrest indicates that full compensation may not be possible when gravity-related signals are absent, raising the question of whether alternative cues, natural or artificially provided (e.g., via augmented reality), could fully substitute for gravity signals in supporting optimal visuo-manual coordination.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eEthics Statement\u003c/p\u003e\n\u003cp\u003eThe experimental protocol was approved by the Universit\u0026eacute; Paris Cit\u0026eacute; ethical committee (N\u0026deg; CER 2014-34/2018\u0026thinsp;\u0026minus;\u0026thinsp;115) and by the French \u0026lsquo;Comit\u0026eacute; de Protection des Personnes\u0026rsquo; (CPP Sud-Ouest et Outre-Mer I, France, number ID RCB: 2016-A00401-50) and all participants gave written informed consent in line with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003eExperimental Setup\u003c/p\u003e\n\u003cp\u003eThe participants wore Oculus Rift1 virtual reality (VR) goggles (field of view: 90◦, frame rate: 90 Hz, resolution: 1080 \u0026times; 1200 pixels, adjustable inter-pupillary distance). A motion-analysis system (CODAmotion; Charnwood Dynamics, sub-millimeter accuracy, 200-Hz sampling frequency) was used for real-time recording of the position of 24 infrared active-markers. These LEDs were placed on the light-weight 3D-printed structures which were fixed to the VR headset (8 LEDs), to the subjects\u0026rsquo; right hand (8 LEDs) and to their chest (8 LEDs) as shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA. Custom C\u0026thinsp;+\u0026thinsp;+\u0026thinsp;code was developed by the research team to combine the information about the three-dimensional position of the infrared markers and the angular velocity of the VR headset (Oculus Rift sensors) to estimate in real-time the position and the orientation of the subject viewpoint and to update accordingly the stereoscopic images shown in the VR goggles. For tracking the hand and chest movements, only infrared markers were used.\u003c/p\u003e\n\u003cp\u003eThe 3D virtual scene shown to the subjects consisted of a cylindrical rocky tunnel (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB-C). To help the subject spatial orientation, metal tubular structures parallel to the tunnel axis were added on the walls: the tubes went from clear on the \u0026ldquo;ceiling\u0026rdquo; to dark on the \u0026ldquo;floor\u0026rdquo; facilitating the identification of the visual vertical.\u003c/p\u003e\n\u003cp\u003eExperimental Paradigm\u003c/p\u003e\n\u003cp\u003eThe task\u003c/p\u003e\n\u003cp\u003eThe task performed by the subjects was similar to the one of our previous studies \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. It can be split in three main phases: 1) acquisition of the target orientation, 2) memorization delay and 3) alignment of the hand to the memorized target.\u003c/p\u003e\n\u003cp\u003e1) In the acquisition phase the subjects had 2.5 seconds to memorize the target orientation that could be laterally tilted of \u0026minus;\u0026thinsp;45\u0026deg;, \u0026minus;\u0026thinsp;30\u0026deg;, \u0026minus;\u0026thinsp;15\u0026deg;, 0\u0026deg;, +\u0026thinsp;15\u0026deg;, +\u0026thinsp;30\u0026deg; or +\u0026thinsp;45\u0026deg; with respect to the virtual vertical. This phase was always performed with the head aligned with the trunk.\u003c/p\u003e\n\u003cp\u003e2) During the delay phase, after the target disappeared, the subjects waited 5 seconds for a visual cue prompting the response. In the first 21 trials of each sensory condition, during this phase, the subjects had to keep the head aligned with the trunk. In the following 56 trials the subjects were guided to tilt the head 15\u0026deg; to the right or to the left. The direction and the amplitude of the head roll to be performed was indicated by a circular arrow and semi-transparent halo spaced around the subject eyes (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC). The halo changed color depending on lateral tilt of the subjects\u0026rsquo; head, going progressively from red to green when approaching the desired head orientation. If at the end of the 5 seconds delay the subjects were unable to maintain the halo green, the trial was interrupted and repeated later on, otherwise a visual \u0026lsquo;go signal\u0026rsquo; appeared, indicating the transition to the following phase.\u003c/p\u003e\n\u003cp\u003e3) During the response phase the subjects had to align the hand to the memorized target, while keeping the head orientation reached after the delay phase. To validate their response the subjects had to press a button on a remote hold in the left hand.\u003c/p\u003e\n\u003cp\u003eIn order to quantify the sensory weighting a sensory conflict was artificially introduced in half of the trials with lateral neck flexion \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e: a gradual, imperceptible conflict was generated such that, when the subjects laterally flexed the neck, they received visual information corresponding to a larger head tilt. The amplitude of the angle between the visual vertical and subject body axis varied proportionally (by a factor of 0.6) with the actual head tilt, so that for a 15\u0026deg; lateral head roll a 9\u0026deg; conflict was generated. When, at the end of the experiment, the subjects were interviewed about the conflict perception, none of them reported to have noticed the tilt of the visual scene.\u003c/p\u003e\n\u003cp\u003eSensory Conditions\u003c/p\u003e\n\u003cp\u003eThe same task was performed in three distinct sensory conditions represented in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB. The main condition is the \u003cem\u003eCross-Modal\u003c/em\u003e condition aimed at investigating the brain ability to encode visual information in the proprioceptive space and vice-versa. Two unimodal conditions were performed to quantify possible effects of prolonged bedrest on Vision and Proprioception respectively.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCross-Modal (V-P) condition\u003c/strong\u003e. The target was presented visually and during the response the hand orientation could be controlled through arm proprioception only. The target consisted of parallel blue beams placed at the end of the tunnel (three meters in front of the subject), as shown in the upper-left panel of Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB. During the response phase, the hand of the subjects was represented as a capsule with the main axis aligned with the prono-supination axis of the hand. In this way only the arm proprioception could be used to control the prono-supination alignment task, whilst all remaining degrees of freedom of the hand, which are task irrelevant, could be also visually controlled.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUni-Modal Visual (V-V) condition.\u003c/strong\u003e Only vision could be used for both target acquisition and response control. The target orientation was presented as blue beams as in the Cross-Modal task. During the response phase the subject kept the hand next to the body and a virtual representation of the hand (central-right part of Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB) appeared in front of the subject eyes with a random orientation. They used the oculus remote right-left buttons to change the virtual hand roll to reproduce the memorized target orientation. Only visual information could be used to estimate the necessary response adjustments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eUni-Modal Proprioceptive (P-P) condition.\u003c/strong\u003e Both target and response orientation could be sensed through proprioception only. The target orientation was not presented as blue beams (bottom-left panel of Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB). To acquire the target lateral tilt, the subjects raised the hand, which was represented as a capsule, as in the response phase of the V-P task, but the color of the capsule changed from red to green when the absolute angular distance between the hand and target roll decreased. The only information available to memorize the target orientation was hence the proprioceptive feedback related to forearm pronation-supination corresponding to the capsule becoming green. After 2.5 sec with the correct hand orientation, that is with a green capsule, the subjects were instructed to lower the arm. The response was controlled using proprioception only, as in Cross-Modal (V-P) task.\u003c/p\u003e\n\u003cp\u003eFor each sensory condition the subject performed 21 (=\u0026thinsp;7 targets x 3 repetitions) trials without head rotations and 56 (=\u0026thinsp;7 targets x 2 head rotations x 2 conflicts x 2 repetitions) trials with lateral neck flexions. Therefore, one experimental session consisted of 231 trials and lasted up to two hours including rests between sensory conditions and breaks every 7 trials.\u003c/p\u003e\n\u003cp\u003eIn order to keep the subject motivated, after the response validation of 102 randomly selected trials (among those without conflict) a hand shaped projectile was casted toward the reappeared blue beams so that the subjects could estimate the accuracy of their response.\u003c/p\u003e\n\u003cp\u003eBedrest and Control protocol\u003c/p\u003e\n\u003cp\u003eA group of 20 healthy male subjects (34+/-8 years hold) participated to the present experiment in the frame of a long-term bedrest campaign (LTBR) sponsored by the European Space Agency (ESA) and performed at the French Institute for Space Medicine and Physiology (MEDES), in Toulouse, France. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eD, the LTBR protocol consisted of 15 days of baseline data collection (BDC), 60 days of -6\u0026deg; head down tilt (HDT) bedrest and 15 days of recovery (R). The subjects participated to a training session 14 day before the HDT phase to get used to the different tasks. They performed an experimental session in the \u003cem\u003eSeated\u003c/em\u003e posture (upper part of Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA) 7 days before the HDT (BDC-7). They were tested three times in the \u003cem\u003eSupine\u003c/em\u003e posture (bottom part of Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC) during the HDT phase: after 2, 30 and 59 days (HDT\u0026thinsp;+\u0026thinsp;2, HDT\u0026thinsp;+\u0026thinsp;30, HDT\u0026thinsp;+\u0026thinsp;59). To perform the task in this condition the special head support described by Bernard-Espina et al. (2022) was used. Finally, they were tested in the \u003cem\u003eSeated\u003c/em\u003e posture at day 2 and 13 of the recovery period (R\u0026thinsp;+\u0026thinsp;2 and R\u0026thinsp;+\u0026thinsp;13).\u003c/p\u003e\n\u003cp\u003eA group of 15 control subjects (30+/-9 years hold) performed the same tasks at the team laboratory, following the same schedule than the bedrest group. This group was not constrained, however, to the HDT posture for two months and the participants continued their daily life activities for the duration of the experiment. All experimental sessions for this group were performed in the \u003cem\u003eSeated\u003c/em\u003e posture, in order to specifically quantify possible learning effects due to the multiple repetitions of the experiment, which is known to occurs especially when feedback about the response errors is provided.\u003c/p\u003e\n\u003cp\u003eData Analyses\u003c/p\u003e\n\u003cp\u003eThe lateral inclination (roll) of the hand when the subject validated the response was analyzed using Matlab (MathWorks, RRID: SCR_001622). To exhaustively describe the performance of each subject several parameters have been computed from their responses. In order to maximize the robustness of the parameters despite the few responses available per each combination of target and head orientation, the procedure described below, and based on linear interpolations, has been used.\u003c/p\u003e\n\u003cp\u003eFirst, for the trials with the head straight (\u003cem\u003eHS\u003c/em\u003e) all responses (\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e) and the corresponding targets (\u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e) are linearly interpolated (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eA) obtaining the regression line\u003c/p\u003e\n\u003cp\u003e\u003cem\u003er\u0026thinsp;=\u0026thinsp;m\u003c/em\u003e\u003csub\u003e\u003cem\u003eHS\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u0026middot;t\u0026thinsp;+\u0026thinsp;q\u003c/em\u003e\u003csub\u003e\u003cem\u003eHS\u003c/em\u003e\u003c/sub\u003e .\u003c/p\u003e\n\u003cp\u003eFor the trials with lateral head tilt (\u003cem\u003eHT\u003c/em\u003e) without conflict, as shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eB-C, the response obtained after the rotation of the head to the right (\u003cem\u003eHR\u003c/em\u003e) and to the left (\u003cem\u003eHL\u003c/em\u003e) are interpolated separately but imposing their parallelism obtaining two regression line\u003c/p\u003e\n\u003cp\u003er\u0026thinsp;=\u0026thinsp;\u003cem\u003em\u003c/em\u003e\u003csub\u003e\u003cem\u003eHT\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u0026middot;t\u0026thinsp;+\u0026thinsp;q\u003c/em\u003e\u003csub\u003e\u003cem\u003eHR\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003er\u0026thinsp;=\u0026thinsp;\u003cem\u003em\u003c/em\u003e\u003csub\u003e\u003cem\u003eHT\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e\u0026middot;t\u0026thinsp;+\u0026thinsp;q\u003c/em\u003e\u003csub\u003e\u003cem\u003eHL\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eThe parallelism between the regression line for the trial \u003cem\u003eHS\u003c/em\u003e and \u003cem\u003eHT\u003c/em\u003e is not imposed, because previous results suggest that tilting the head could affect the slope of the regression line \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eOnce computed, the coefficients of the regression lines are used to estimate all parameters describing the individual performances.\u003c/p\u003e\n\u003cp\u003eFor each experimental session and sensory condition, the subject \u003cstrong\u003eprecision\u003c/strong\u003e is quantified by computing the variability of the \u003cem\u003eN\u003c/em\u003e responses, as \u003cem\u003eMean Squared Deviation\u003c/em\u003e (\u003cstrong\u003eMSD\u003c/strong\u003e) from the corresponding regression lines.\u003c/p\u003e\n\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e$$\\:MSD=\\frac{\\sum\\:_{i\\in\\:HS}{\\left({m}_{HS}\u0026middot;{t}_{i}+{q}_{HS}-{r}_{i}\\right)}^{2}+\\sum\\:_{i\\in\\:HR}{\\left({m}_{HT}\u0026middot;{t}_{i}+{q}_{HR}-{r}_{i}\\right)}^{2}+\\sum\\:_{i\\in\\:HL}{\\left({m}_{HT}\u0026middot;{t}_{i}+{q}_{HL}-{r}_{i}\\right)}^{2}}{N}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eAlthough taking the square root of MSD would have yielded a more intuitive variability parameter expressed in degrees, this transformation would not have allowed a correct computation of between-sessions differences. As it will be shown, these differences are essential for data normalization and thus to an effective analysis of the HDT effect.\u003c/p\u003e\n\u003cp\u003eThe \u003cstrong\u003eaccuracy\u003c/strong\u003e was represented by the responses\u0026rsquo; Total Deviation (\u003cstrong\u003eTDev\u003c/strong\u003e) and computed as the average absolute distance between the responses regression lines and the line passing through the targets\u0026rsquo; positions, represented in the following equations by the terms \u003cem\u003e15\u0026deg;nt\u003c/em\u003e, where \u003cem\u003ent\u003c/em\u003e identifies the target number from \u0026minus;\u0026thinsp;3 to +\u0026thinsp;3:\u003c/p\u003e\n\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e$$\\:TDev=\\sum\\:_{nt=-3}^{3}\\left(\\left|{m}_{HS}\\left(15^\\circ\\:nt\\right)+{q}_{HS}-15^\\circ\\:nt\\right|+\\left|{m}_{HT}\\left(15^\\circ\\:nt\\right)+{q}_{HR}-15^\\circ\\:nt\\right|+\\left|{m}_{HT}\\left(15^\\circ\\:nt\\right)+{q}_{HL}-15^\\circ\\:nt\\right|\\right)/21$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe \u003cstrong\u003edistortion\u003c/strong\u003e \u003cem\u003e(\u003c/em\u003e\u003cstrong\u003eDist\u003c/strong\u003e\u003cem\u003e)\u003c/em\u003e, representing possible over/under-estimation of the distance between the targets\u0026rsquo; orientation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e, is represented by the average angle between the regression lines and the line passing through the targets\u0026rsquo; orientations:\u003c/p\u003e\n\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e$$\\:Dist=\\frac{\\left(\\sum\\:_{c=HS,HT}\\text{atan}\\left({m}_{c}\\right)-45^\\circ\\:\\right)}{2}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003ePositive and negative values of \u003cem\u003eDist\u003c/em\u003e correspond to a global over- and under- estimation of the angular distances, respectively.\u003c/p\u003e\n\u003cp\u003eThe \u003cstrong\u003eAubert-M\u0026uuml;ller effect\u003c/strong\u003e \u003cem\u003e(\u003c/em\u003e\u003cstrong\u003eAMe\u003c/strong\u003e\u003cem\u003e)\u003c/em\u003e, corresponding to the global response bias due to the lateral neck flexion\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, was quantified as half of the algebraic distance between the intersection point of the two \u003cem\u003eHT\u003c/em\u003e regression lines with the vertical axis:\u003c/p\u003e\n\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e$$\\:AMe=({q}_{HL}-{q}_{HR})/2$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003ePositive and negative values of \u003cem\u003eAMe\u003c/em\u003e correspond to a global deviation of the responses in the same and opposite direction than the head tilt, respectively.\u003c/p\u003e\n\u003cp\u003eGiven the importance of the sign for the interpretation of the two later parameters, \u003cem\u003eDist\u003c/em\u003e and \u003cem\u003eAMe\u003c/em\u003e, in the result representation the grand average of the BDC-7 session has been added to the normalized values (see statistical analyses).\u003c/p\u003e\n\u003cp\u003eSensory weighting estimation\u003c/p\u003e\n\u003cp\u003eIn order to quantify the relative weight associated to the visual encoding of the sensory information, the deviation of the responses due to the imperceptible tilt of the visual scene has been computed. To quantify the specific effect of the sensory conflict in each condition we linearly interpolated the responses of the trials with conflicts with right and left neck flexion constraining the lines to be parallel to regression lines of the no-conflict-trials (see Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eB-C). This procedure provides the response-axis intercepts for the conflict trials. Subtracting to these parameters the corresponding values in the no-conflict-trials we obtain the average deviations of the response due to the tilt of the visual scene: \u003cem\u003e\u0026Delta;q\u003c/em\u003e\u003csub\u003e\u003cem\u003er,Hi\u003c/em\u003e\u003c/sub\u003e. In order to convert the response deviation into the percentage weight given to visual information, we computed, for each conflict trial, the virtual displacement of the target expected if only visual information was used to code its orientation, which corresponds to \u003cem\u003e-head_angle\u003c/em\u003e \u0026times; \u003cem\u003e0.6\u003c/em\u003e. We linearly interpolated these theoretical responses for right and left neck flexion separately, constraining the lines to be parallel to the one joining the targets (\u003cem\u003em\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1) and we obtained the vertical axis intercepts. Subtracting from these parameters the intercept of the line joining the target in the no-conflict trials (\u003cem\u003eq\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0), we obtain the average target deviation expected in case of fully visual encoding of their orientation: \u003cem\u003e\u0026Delta;q\u003c/em\u003e\u003csub\u003e\u003cem\u003et,Hi\u003c/em\u003e\u003c/sub\u003e. The percentage weight given to the visual information, \u0026omega;\u003csub\u003e\u003cem\u003eV\u003c/em\u003e\u003c/sub\u003e, can be then computed as it follows:\u003c/p\u003e\n\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e$$\\:{\\omega\\:}_{V}=\\frac{1}{2}\\sum\\:_{d=L,R}\\frac{\\varDelta\\:{q}_{r,hi}}{\\varDelta\\:{q}_{t,hi}}\\bullet\\:100\\%$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eStatistical analyses\u003c/p\u003e\n\u003cp\u003eIn order to compensate for initial between-subjects\u0026rsquo; differences, as for instance subject sensory acuity or motor precision, all results are expressed as a difference (\u0026Delta;) with respect to BDC-7 session, which results in a normalization of the results. Then, in order to specifically quantify the effect of the bedrest, for each following session we compared the distribution of the results of the Bedrest subjects with respect to the corresponding Controls\u0026rsquo; session. As the parameters resulted normally distributed (Anderson-Darling test) the comparison between the Bedrest and Control groups were performed by using parametric independent t-tests. The one-tailed version of this test was employed, since our previous experimental study on the acute effects of the supine posture \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and our optimal sensory integration theory \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e provide very clear hypotheses on the expected effects of the bedrest: increase of all the computed parameters (response variability, \u003cem\u003eMSD\u003c/em\u003e; response total deviation, \u003cem\u003eTDev\u003c/em\u003e; visual weight, \u0026omega;\u003csub\u003eV\u003c/sub\u003e ; Distortion, \u003cem\u003eDist\u003c/em\u003e; and Aubert-Muller effect, \u003cem\u003eAMe\u003c/em\u003e). In order to compensate for a possible increase of type I errors due to performing five comparisons (for HDT\u0026thinsp;+\u0026thinsp;2, HDT\u0026thinsp;+\u0026thinsp;30, HDT\u0026thinsp;+\u0026thinsp;59, R\u0026thinsp;+\u0026thinsp;2, R\u0026thinsp;+\u0026thinsp;13) the Benjamini-Hochberg correction was applied to the results of the Wilcoxon tests.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthors Contributions\u003c/h2\u003e\n\u003cp\u003eMT, JM conceptualized the experiment; MT, JM, MB acquired the funding; MT, JM designed the experiment; JM, MT programmed the stimulus; MT collected the data; MT, JM, MB discussed and interpreted the data; MT performed the statistical analysis and wrote the first draft; MT, JM, MB revised the paper.\u003c/p\u003e\n\u003ch2\u003eCompeting Interest\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eThe authors have no competing interests as defined by Nature Portfolio, or other interests that might be perceived to influence the results and/or discussion reported in this paper.\u003c/p\u003e\n\u003ch2\u003eAcknowledgements\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eThe authors thank M. Patrice Jegouzo for his technical help in designing the experimental setup. This work was supported by the Centre National des Etudes Spatiales (CNES) and the European Space Agency (ESA). This study contributes to the IdEx Université de Paris ANR-18-IDEX-0001.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis research was founded by the Centre National des Etudes Spatiales (CNES), the Centre National de la Recherche Scientifique (CNRS) and Université Paris Cité.\u003c/p\u003e\n\u003ch2\u003eData availability\u003c/h2\u003e\n\u003cp\u003eData will be made available on reasonable request to Mr. Michele Tagliabue ([email protected]).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBernard-Espina, J., Dal Canto, D., Beraneck, M., McIntyre, J. \u0026amp; Tagliabue, M. How Tilting the Head Interferes With Eye-Hand Coordination: The Role of Gravity in Visuo-Proprioceptive, Cross-Modal Sensory Transformations. \u003cem\u003eFront. Integr. Neurosci.\u003c/em\u003e 16, (2022).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAndersen, R. A., Snyder, L. H., Li, C. S. \u0026amp; Stricanne, B. Coordinate transformations in the representation of spatial information. \u003cem\u003eCurr Opin Neurobiol\u003c/em\u003e 3, 171\u0026ndash;176 (1993).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCohen, Y. E. \u0026amp; Andersen, R. A. A common reference frame for movement plans in the posterior parietal cortex. \u003cem\u003eNat Rev Neurosci\u003c/em\u003e 3, 553\u0026ndash;562 (2002).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSoechting, J. F. \u0026amp; Flanders, M. Errors in pointing are due to approximations in sensorimotor transformations. \u003cem\u003eJ Neurophysiol\u003c/em\u003e 62, 595\u0026ndash;608 (1989).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSabes, P. N. Sensory integration for reaching: models of optimality in the context of behavior and the underlying neural circuits. \u003cem\u003eProg Brain Res\u003c/em\u003e 191, 195\u0026ndash;209 (2011).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTagliabue, M. \u0026amp; McIntyre, J. A modular theory of multisensory integration for motor control. \u003cem\u003eFront Comput Neurosci\u003c/em\u003e 8, 1 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHenriques, D. Y., Klier, E. M., Smith, M. A., Lowy, D. \u0026amp; Crawford, J. D. Gaze-centered remapping of remembered visual space in an open-loop pointing task. \u003cem\u003eJ Neurosci\u003c/em\u003e 18, 1583\u0026ndash;1594 (1998).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMcIntyre, J., Stratta, F. \u0026amp; Lacquaniti, F. Viewer-centered frame of reference for pointing to memorized targets in three-dimensional space. \u003cem\u003eJ Neurophysiol\u003c/em\u003e 78, 1601\u0026ndash;1618 (1997).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMcIntyre, J., Stratta, F. \u0026amp; Lacquaniti, F. Short-term memory for reaching to visual targets: psychophysical evidence for body-centered reference frames. \u003cem\u003eJ Neurosci\u003c/em\u003e 18, 8423\u0026ndash;8435 (1998).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMcGuire, L. M. M. \u0026amp; Sabes, P. N. Sensory transformations and the use of multiple reference frames for reach planning. \u003cem\u003eNat Neurosci\u003c/em\u003e 12, 1056\u0026ndash;1061 (2009).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTagliabue, M. \u0026amp; McIntyre, J. Necessity is the Mother of Invention: Reconstructing Missing Sensory Information in Multiple, Concurrent Reference Frames for Eye-Hand Coordination. \u003cem\u003eJ Neurosci\u003c/em\u003e 31, 1397\u0026ndash;1409 (2011).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHenriques, D. Y. P., Medendorp, W. P., Gielen, C. C. A. M. \u0026amp; Crawford, J. D. Geometric computations underlying eye-hand coordination: orientations of the two eyes and the head. \u003cem\u003eExp Brain Res\u003c/em\u003e 152, 70\u0026ndash;78 (2003).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchlicht, E. J. \u0026amp; Schrater, P. R. Impact of coordinate transformation uncertainty on human sensorimotor control. \u003cem\u003eJ Neurophysiol\u003c/em\u003e 97, 4203\u0026ndash;4214 (2007).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAbedi Khoozani, P. \u0026amp; Blohm, G. Neck muscle spindle noise biases reaches in a multisensory integration task. \u003cem\u003eJ. Neurophysiol.\u003c/em\u003e 120, 893\u0026ndash;909 (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBurns, J. K. \u0026amp; Blohm, G. Multi-sensory weights depend on contextual noise in reference frame transformations. \u003cem\u003eFront Hum Neurosci\u003c/em\u003e 4, 221 (2010).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTagliabue, M., Arnoux, L. \u0026amp; McIntyre, J. Keep your head on straight: Facilitating sensori-motor transformations for eye-hand coordination. \u003cem\u003eNeuroscience\u003c/em\u003e 248, 88\u0026ndash;94 (2013).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePaillard, J. Brain and Space. in (ed. J.Paillard) 461\u0026ndash;481 (Oxford University Press, 1991).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAdamopoulos, K., Koutsouris, D., Zaravinos, A. \u0026amp; Lambrou, G. I. Gravitational Influence on Human Living Systems and the Evolution of Species on Earth. \u003cem\u003eMol. Basel Switz\u003c/em\u003e. 26, (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMcIntyre, J., Zago, M., Berthoz, A. \u0026amp; Lacquaniti, F. Does the brain model Newton\u0026rsquo;s laws? \u003cem\u003eNat Neurosci\u003c/em\u003e 4, 693\u0026ndash;694 (2001).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eArnoux, L. \u003cem\u003eet al.\u003c/em\u003e The visual encoding of purely proprioceptive intermanual tasks is due to the need of transforming joint signals, not to their interhemispheric transfer. \u003cem\u003eJ. Neurophysiol.\u003c/em\u003e 118, 1598\u0026ndash;1608 (2017).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTagliabue, M. \u0026amp; McIntyre, J. When Kinesthesia Becomes Visual: A Theoretical Justification for Executing Motor Tasks in Visual Space. \u003cem\u003ePLoS ONE\u003c/em\u003e 8, e68438 (2013).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eErnst, M. O. \u0026amp; Banks, M. S. Humans integrate visual and haptic information in a statistically optimal fashion. \u003cem\u003eNature\u003c/em\u003e 415, 429\u0026ndash;433 (2002).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSober, S. J. \u0026amp; Sabes, P. N. Flexible strategies for sensory integration during motor planning. \u003cem\u003eNat Neurosci\u003c/em\u003e 8, 490\u0026ndash;497 (2005).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa, W. J., Beck, J. M., Latham, P. E. \u0026amp; Pouget, A. Bayesian inference with probabilistic population codes. \u003cem\u003eNat Neurosci\u003c/em\u003e 9, 1432\u0026ndash;1438 (2006).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFetsch, C. R., Pouget, A., DeAngelis, G. C. \u0026amp; Angelaki, D. E. Neural correlates of reliability-based cue weighting during multisensory integration. \u003cem\u003eNat Neurosci\u003c/em\u003e 15, 146\u0026ndash;154 (2012).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFetsch, C. R., DeAngelis, G. C. \u0026amp; Angelaki, D. E. Bridging the gap between theories of sensory cue integration and the physiology of multisensory neurons. \u003cem\u003eNat. Rev. Neurosci.\u003c/em\u003e 14, 429\u0026ndash;442 (2013).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBanker, L. A. \u003cem\u003eet al.\u003c/em\u003e The effects of a spaceflight analog with elevated CO2 on sensorimotor adaptation. \u003cem\u003eJ. Neurophysiol.\u003c/em\u003e 125, 426\u0026ndash;436 (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKoppelmans, V. \u003cem\u003eet al.\u003c/em\u003e Exercise as potential countermeasure for the effects of 70 days of bed rest on cognitive and sensorimotor performance. \u003cem\u003eFront. Syst. Neurosci.\u003c/em\u003e 9, (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMorfoisse, T. \u003cem\u003eet al.\u003c/em\u003e Modality-independent effect of gravity in shaping the internal representation of 3D space for visual and haptic object perception. \u003cem\u003eJ. Neurosci. Off. J. Soc. Neurosci.\u003c/em\u003e 44, e2457202023 (2024).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCarriot, J., Mackrous, I. \u0026amp; Cullen, K. E. Challenges to the Vestibular System in Space: How the Brain Responds and Adapts to Microgravity. \u003cem\u003eFront. Neural Circuits\u003c/em\u003e 15, 760313 (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMikellidou, K., Cicchini, G. M., Thompson, P. G. \u0026amp; Burr, D. C. The oblique effect is both allocentric and egocentric. \u003cem\u003eJ. Vis.\u003c/em\u003e 15, 24 (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarnett-Cowan, M., Snow, J. C. \u0026amp; Culham, J. C. Contribution of Bodily and Gravitational Orientation Cues to Face and Letter Recognition. \u003cem\u003eMultisensory Res.\u003c/em\u003e 28, 427\u0026ndash;442 (2015).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarendaz, C., Stivalet, P., Barraclough, L. \u0026amp; Walkowiac, P. Effect of gravitational cues on visual search for orientation. \u003cem\u003eJ. Exp. Psychol. Hum. Percept. Perform.\u003c/em\u003e 19, 1266\u0026ndash;1277 (1993).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGammeri, R. \u003cem\u003eet al.\u003c/em\u003e Modulation of vestibular input by short-term head-down bed rest affects somatosensory perception: implications for space missions. \u003cem\u003eFront. Neural Circuits\u003c/em\u003e 17, (2023).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuerraz, M., Poquin, D. \u0026amp; Ohlmann, T. The role of head-centric spatial reference with a static and kinetic visual disturbance. \u003cem\u003ePercept Psychophys\u003c/em\u003e 60, 287\u0026ndash;295 (1998).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuerraz, M., Luyat, M., Poquin, D. \u0026amp; Ohlmann, T. The role of neck afferents in subjective orientation in the visual and tactile sensory modalities. \u003cem\u003eActa Otolaryngol\u003c/em\u003e 120, 735\u0026ndash;738 (2000).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuerraz, M., Caudron, S., Thomassin, N. \u0026amp; Blouin, J. Influence of head orientation on visually and memory-guided arm movements. \u003cem\u003eActa Psychol Amst\u003c/em\u003e 136, 390\u0026ndash;398 (2011).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTempleton, W. B. The role of gravitational cues in the judgement of visual orientation. \u003cem\u003ePercept. Psychophys.\u003c/em\u003e 14, 451\u0026ndash;457 (1973).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCheng, S. \u0026amp; Sabes, P. N. Calibration of Visually Guided Reaching Is Driven by Error-Corrective Learning and Internal Dynamics. \u003cem\u003eJ. Neurophysiol.\u003c/em\u003e 97, 3057\u0026ndash;3069 (2007).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEggert, T., Henriques, D. Y. P., Hart, B. M. \u0026rsquo;t \u0026amp; Straube, A. Modeling inter-trial variability of pointing movements during visuomotor adaptation. \u003cem\u003eBiol. Cybern.\u003c/em\u003e 115, 59\u0026ndash;86 (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSmith, M. A., Ghazizadeh, A. \u0026amp; Shadmehr, R. Interacting adaptive processes with different timescales underlie short-term motor learning. \u003cem\u003ePLoS Biol\u003c/em\u003e 4, e179 (2006).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLee, J. K. \u003cem\u003eet al.\u003c/em\u003e Head Down Tilt Bed Rest Plus Elevated CO2 as a Spaceflight Analog: Effects on Cognitive and Sensorimotor Performance. \u003cem\u003eFront. Hum. Neurosci.\u003c/em\u003e 13, (2019).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHarris, L. R., Jenkin, M. \u0026amp; Herpers, R. Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright. \u003cem\u003eJ. Vestib. Res.\u003c/em\u003e 32, 325\u0026ndash;340 (2022).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOng, J., Lee, A. G. \u0026amp; Moss, H. E. Head-Down Tilt Bed Rest Studies as a Terrestrial Analog for Spaceflight Associated Neuro-Ocular Syndrome. \u003cem\u003eFront. Neurol\u003c/em\u003e. 12, (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBernauer, E. \u003cem\u003eet al.\u003c/em\u003e Knee-joint proprioception during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training. \u003cem\u003eAviat. Space Environ. Med.\u003c/em\u003e 65, 1110?1115 (1994).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKouzaki, M. \u003cem\u003eet al.\u003c/em\u003e Effects of 20-day bed rest with and without strength training on postural sway during quiet standing. \u003cem\u003eActa Physiol. Oxf. Engl.\u003c/em\u003e 189, 279\u0026ndash;292 (2007).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eReschke, M. F. \u003cem\u003eet al.\u003c/em\u003e Postural Reflexes, Balance Control, and Functional Mobility with Long-Duration Head-Down Bed Rest. \u003cem\u003eAviat. Space Environ. Med.\u003c/em\u003e 80, A45\u0026ndash;A54 (2009).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYamanaka, K. \u003cem\u003eet al.\u003c/em\u003e The effects of long-term bed rest on H-reflex and motor evoked potential in the human soleus muscle during standing. \u003cem\u003eNeurosci. Lett.\u003c/em\u003e 266, 101\u0026ndash;104 (1999).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBelav\u0026yacute;, D. L. \u003cem\u003eet al.\u003c/em\u003e Differential atrophy of the lower-limb musculature during prolonged bed-rest. \u003cem\u003eEur. J. Appl. Physiol.\u003c/em\u003e 107, 489\u0026ndash;499 (2009).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXiong, Z., Tian, Y., Wang, X., Wei, K. \u0026amp; Bi, Y. Gravity matters for the neural representations of action semantics. \u003cem\u003eCereb. Cortex\u003c/em\u003e 33, 6862\u0026ndash;6871 (2023).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBernard-Espina, J., Beraneck, M., Maier, M. A. \u0026amp; Tagliabue, M. Multisensory Integration in Stroke Patients: A Theoretical Approach to Reinterpret Upper-Limb Proprioceptive Deficits and Visual Compensation. \u003cem\u003eFront. Neurosci.\u003c/em\u003e 15, 319 (2021).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchoenmaekers, C. \u003cem\u003eet al.\u003c/em\u003e Neural correlates of vestibular adaptation in cosmonauts after long duration spaceflight. \u003cem\u003eNPJ Microgravity\u003c/em\u003e 11, 71 (2025).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStein, B. E., Stanford, T. R. \u0026amp; Rowland, B. A. Development of multisensory integration from the perspective of the individual neuron. \u003cem\u003eNat. Rev. Neurosci.\u003c/em\u003e 15, 520\u0026ndash;535 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMcIntyre, J. \u0026amp; Lipshits, M. Central processes amplify and transform anisotropies of the visual system in a test of visual-haptic coordination. \u003cem\u003eJ Neurosci\u003c/em\u003e 28, 1246\u0026ndash;1261 (2008).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7935209/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7935209/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Human eye-hand coordination relies on the integration of visual and proprioceptive cues, a process influenced by gravitational inputs1. This study investigates whether the human preference for an upright head posture during visuomotor tasks results from evolutionary constraints (phylogeny) or individual adaptation (ontogeny). Volunteers completed 60 days of bedrest, performing virtual reality tests assessing their performance in cross-modal visuo-proprioceptive, unimodal visual, and unimodal proprioceptive tasks. Compared with controls, bedrest participants initially exhibited impaired cross-modal transformations, followed by partial adaptation. However, after resuming an upright posture, their responses variability and visual dependency remained greater than in controls, indicating lasting effects of prolonged head-gravity misalignment. These findings support an ontogenetic basis for the preference for a gravitationally-aligned head posture, with implications for spaceflight adaptation and vestibular rehabilitation.","manuscriptTitle":"Adaptation of multisensory integration for visuo-manual coordination during 60 days of bedrest","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-18 17:22:18","doi":"10.21203/rs.3.rs-7935209/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8920e514-a211-41b9-8429-63c0a1fb1b66","owner":[],"postedDate":"November 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":58064740,"name":"Biological sciences/Neuroscience"},{"id":58064741,"name":"Biological sciences/Psychology"},{"id":58064742,"name":"Social science/Psychology"}],"tags":[],"updatedAt":"2026-03-16T03:40:19+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-18 17:22:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7935209","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7935209","identity":"rs-7935209","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}