Perceptual binding occurs independently beyond early neural adaptation stages in human color cone pathways

Perceptual binding occurs independently beyond early neural adaptation stages in human color cone pathways | 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 Perceptual binding occurs independently beyond early neural adaptation stages in human color cone pathways Francisca C. Matias, João Castelhano, Miguel Castelo-Branco This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3301293/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 Color perception entails competing temporal context mechanisms such as adaptation versus memory persistence 1 . Perceptual dynamics in color cone pathways can be studied using the phenomenon of hysteresis, well-known in the framework of physical dynamical systems. It postulates analogous mechanisms: a) visual persistence defining positive hysteresis b) adaptation or habituation (negative hysteresis). Adaptation causes early perceptual switches to competing states. We investigated competition between these mechanisms in human color cone pathways. Color adaptation occurs within early visual pathways up to V4, involved in local scene analysis, but it is unknown if they underlie global perceptual binding of visual elements 2 . We tested if the neural locus of perceptual binding occurs at visual and memory stages beyond the locus of color adaptation, using a dynamic color matching task in cone contrast space, along Blue-Yellow (S-(L + M) and Green-Red processing channels (L-M). Simple vs Compound stimuli required or not holistic perceptual binding, under visual or memory-guided conditions. Adaptation (negative hysteresis) dominated for the former condition, was stored in memory, but vanished when binding was required either in vision or memory. In sum, cone pathway adaptation mechanisms dominate in early vision, while perceptual binding occurs at a second stage as predicted by the feature integration theory. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Quantitative studies of the dynamics of perception are important to investigate its dependence on history and context1 1–3 . Perceptual decision if often difficult because of the inherently ambiguous choice between distinct interpretations of the sensory world which can be influenced by factors such as attention, prior probability of the occurrence of an event and previous outcomes 4 . A related important question is whether holistic integration under ambiguous sensory contexts and gestalt perceptual formation occur at early visual levels 5 , 6 . It is known that perceptual decisions are controlled by high level, integrative top-down factors, like prior knowledge and bottom-up factors that reflect sensory input 2 , 7 . The binding problem of how visual processing leads to merging local elements them into a global holistic representation remains strongly debated. This problem refers to the scientific challenge of identifying mechanisms that may achieve the integration of local elements into global percepts 8 , 9 . Although mechanisms for local contextual processing are well-known to occur at early visual levels 2 , the neural locus of global binding remains elusive. Several theories have been raised to explain perceptual binding, namely the feature integration theory, which postulates that it is a separable high level process, where attention serves as a mechanistic “glue” for visual binding 10 . An alternative account postulates that binding is instantiated at early visual levels, by a binding by synchrony mechanism 11 , 12 .´ Colour adaptation can be used as a tool to address this question because it occurs within early visual pathways up to V4, which are involved in local scene analysis 1 . Therefore if the neural locus binding occurs at these early levels, it should be sensitive to adaptation mechanisms. These mechanisms can be tested by the study of adaptation along chromatic pathways defined in cone contrast space. The LMS color space, also known as the cone-opponent color space, is a color model based on the responses of the three types of cones in the human visual system: the long-wavelength (L)(red) cones, the medium-wavelength (M)(green) cones, and the short-wavelength (S)(blue) cones. These cones are responsible for detecting different ranges of light wavelengths 13 . It is widely used in color vision research and provides a valuable tool for understanding color perception and visual processing, since it can be used to analyse and manipulate color stimuli based on the specific responses along given chromatic axes corresponding to specific pathways 14 – 17 . It is however important in such experiments to not deviate from the isoluminant plane and to take measures to prevent the use of non chromatic cues. As stated above adaptation occurs from the retinal processing to early visual processing levels, and can be described as a phenomenon where prolonged exposure to a specific sensory stimulus leads to changes in neural responses, ultimately impacting perception 18 . Adaptation effects have been observed in specific visual features, including orientation, motion direction, spatial frequency, and face identity. 19 , 20 . Perceptual binding refers to the process by which the brain combines various visual features, such as color, shape, motion, and texture, into a unified and coherent perception of objects and scenes 10 . It remains an open question whether binding reflects an hierarchical, involving process multiple stages of information processing in the visual system 10 , 21 , or instead it is instantiated in widespread neural assemblies 12 . At the initial stages of visual processing, basic features, such as color and orientation, are extracted by specialized cells in the primary visual cortex (V1) 10 , 21 , 22 . These features are represented in separate neural channels or feature maps. Integration of visual information occurs through reciprocal connections and feedback mechanisms 10 , 21 , 23 . According to this view, the hierarchical nature of visual processing allows for the integration of increasingly complex information, leading to the formation of meaningful and coherent representations of the visual world 10 , 21 , 23 . This view is consistent with feature integration theory, but an alternative mechanism is binding by synchronization, and this research question remains highly debated. One way to answer the research question whether binding occurs at processing level immune to low level processing mechanisms is to probe it with early level physiological adaptation. Adaptation is one mechanism contributing to phenomena such as hysteresis. Positive and negative hysteresis are well known phenomena in the physical, biological and psychological sciences 3 , 7 (Fig. 1 ). The former occurs when the change in perceptual switching is delayed (positive lag, corresponding to a sort of short-term memory or persistence. Negative hysteresis reflects the opposing phenomenon of adaptation/fatigue leading to earlier perceptual switches than predicted in the absence of stimulus history (Fig. 1 ). The corresponding early transitions (negative lags) have therefore a hallmark of adaptation/habituation mechanisms 3 , 7 . The study of hysteresis therefore innovatively links two very important neural processes, neural fatigue and short-term memory, and opens windows into understanding their relation with perceptual integration and visual binding. To provide generalization, we tested this hypothesis under visually or memory-guided conditions. Our first research question was whether positive or negative hysteresis occur in color processing pathways. Previous studies in other perceptual domains used paradigms such as letter recognition 25 , emotion recognition 7 , 26 , 27 , binocular rivalry 28 , 29 , motion 3 , 30 , 31 . In most cases positive hysteresis tended to dominate. Here we aimed to understand the dominant outcome of the competition between adaptation and visual persistence in color pathways. Our study directly compared competition between these mechanisms (Fig. 2 ). The central question was however to understand whether perceptual binding, defined as the holistic integration of global patterns based on local elements (Fig. 3 ), is sensitive to the effects of adaptation. If this were not the case, then this would imply that its neural locus is at a higher stage. In sum, we manipulated color along axes (L-M and S-(L + M) cone contrast space related to parvo and koniocellular pathways, respectively, to address the following research questions: If hysteresis occurs in dynamic color matching trajectories does adaptation, as indexed by negative hysteresis, dominate instead of visual persistence (indexed by positive hysteresis)? Is perceptual binding a unaffected by visual adaptation under visual and memory guided matching? If this is the case, this would place the neural underpinnings of binding at a level beyond early visual processing where perceptual and memory representations converge, consistent with the feature integration theory, whereby bound object/surface representations processed at a stage beyond sensory feature processing. Results For analysis if hysteresis for all color trajectory conditions, we determined the ordinal point positions where a dynamic color match occurred. Before that, we first established the relation between the static matching point of subjective equality and veridical physical reference (corresponding to a veridical, non-subjective, true physical match). Subjective equality of a static target to the reference color was determined by the control perceptual matching experiments, in the absence of dynamic color changes, and was found to be statistical similar to the (veridical) Reference Color (RC) of the control condition. This demonstrates that there was no significant difference between the point of subjective equality and veridical physical reference. We found significant negative perceptual hysteresis in the Simple Color Matching experiments for both cone contrast channels and directions (Fig. 4 , Top panels; p < 0.001 for all t tests comparing perceptual curves along Green-Red and Blue-Yellow axes in both directions with Veridical Reference Color; t values ranged from − 4,4 to – 5,8). These effects were replicated when using the subjectively determined neutral midpoint instead of the veridical reference color (RC) (Fig. 4 ). Results are depicted in full tabular form in supplementary Tables 2 and 3. Negative hysteresis was also replicated for Simple Memory Guided task (Fig. 4 , Bottom panels, p < 0.001, t ranging from − 6,6 to -7,7) except for the Blue-Yellow direction, where the effect was marginal (t = -1,968; p = .064). Concerning stimuli requiring holistic binding, hysteresis vanished regardless of using veridical or a reference point of subjective equality, for visually guided binding (Fig. 5 , top panels). The same held true for memory guided binding (Fig. 5 , bottom panels), with the notable exception of the yellow-blue channel (t = -5.273; p < .001; t = -3.389; p = 0.003; Veridical Reference Color, Perceived Reference Control Curve, respectively). In sum, we observed significant negative hysteresis both in visually guided and Simple Match from Memory experiment for the M-L parvocellular related pathway (Green-Red cone contrast Channel) in both directions and the koniocellular pathway with the exception of the Blue-Yellow direction in the memory task. Remarkably, when the task required perceptual binding hysteresis was virtually absent with the single notable exception of the Direction Blue to Blue in the Memory task (for full statistics, See Supplementary Tables 2 and 3 and for visualization of effects sees Figs. 4 and 5 ) Discussion In this study we found that color perception is characterized by strong negative hysteresis, unlike other perceptual domains like motion perception or emotion recognition, where positive hysteresis dominates. This observation occurred specifically for simple and memory-based color matching tasks. Regarding our core research question, the effects of adaptation were not present when perceptual binding was required, regardless of whether it was visually or memory-guided. Taken together, these observations demonstrate that the locus of perceptual binding is beyond early visual processing. We took advantage of the phenomenon of hysteresis to quantify the impact of adaptation. This allowed to dissect mechanisms underlying the relative role of sensory/low level processes and visual persistence memory mechanisms and in particular if perceptual binding is changed by low level adaptation. Our color matching hysteresis based paradigm allowed to show that adaptation is a winning mechanism when competing versus visual persistence in terms of temporal context. The independence from adaptation shows that binding is a separable high level process, which is consistent with the feature integration theory (FIT) theory postulated by Treisman and Gelade that stated that binding occurs at higher levels, when attention is needed for the integration to occur 10 . To ensure that we could isolate chromatic pathways, the mechanisms underpinning perceptual hysteresis were investigated by manipulating trajectories in cone contrast space (L-M and S-(L + M) channels). We first aimed to determine which mechanism, persistence or adaptation, dominated in perception as indexed by signatures of positive and negative hysteresis, respectively 3 . Regarding visual perceptual hysteresis, prior work suggested dominance of positive hysteresis in most visual domains 7 , 32 , 33 . This is to our knowledge the first study of hysteresis on color perception, and we found that negative hysteresis dominated in this case and that binding overruled this mechanism. This provides evidence that temporal effects in perception are dependent on the level of visual processing. Accordingly, the comparison of hysteresis effects in color matching requiring or not perceptual binding (necessary for the hard integration of compound stimuli) shows that they only occur for simple low level tasks at neural locus of adaptation. When binding is required it show to be independent to adaptation properties in low level vision, regardless of whether feature integration is visually or memory guided. This places this type of visual integration process at a second stage of visual processing, as predicted by the attention feature binding hypothesis of Treisman 10 . It is important to point out that hysteresis features a form of study of serial dependence and it was therefore important to avoid in our stimulus presentation the presence of color aftereffects in which prolonged exposure to a particular color stimulus leads to a temporary shift to the perception of complementary colors. 34 , 35 This is in fact demonstrates the existence of opponent channels such as the ones studied here, because the underlying mechanisms is also neural in color-sensitive neurons 34 , 35 . Our participants never reported the presence of color aftereffects and that could not possibly be happening since the exposure to a given stimulus was very short within a stimulis stream color aftereffects require prolonged exposure to a specific color stimulus 34 – 36 . Regarding the simple matching conditions, negative hysteresis was discovered both in direct Color Matching and Memory conditions, for both cardinal channels of color vision, which is consistent with the notion that adaptation can be stored in memory, with the single exception for the memory task in blue to green transitions. When moving from the source color passing through the veridical physical reference (true reference color), the perceptual flip happened similarly in both directions, yet prior to the appearance of the true reference (lag < 0, characteristic of negative hysteresis). In the same line, and as a replication analysis, when compared to the subjective reference as measured using the control experiments (reference measured experimentally with the absence of stimulus history), the same results were found. The identification of such robust negative hysteresis is quite interesting and a surprising outcome since the most widely investigated hysteresis phenomena in the realm of visual perception are characterized by a positive hysteresis lag signature 7 , 32 , 33 or a balanced competition of both adaptation and persistence 27 , 31 , 37 , 38 whilst here we identified a strong effect for adaptation (a winner-take-all mechanisms against visual persistence). This shows that when matching the color visually or in a memory-guided manner, participants report a change earlier than expected in absence of history. Concerning color, there are no studies with hysteresis, which is a very different phenomenon when compared with earlier studies on short term color memory 14 , 16 , 39 – 42 . When there is a delay in time between reference and matching stimuli, memory allocation or successive matching occurs 15 . There are often differences between the original and the memory-matched color, usually represented by hue, brightness and saturation shifts of the matched stimulus even if the luminance stays the same 17 , 41 . The literature points out that color memory tends to emphasize the chromatic attributes, mostly by saturation and lightness increases 15 , 39 . Color memory is expectedly more variable in fidelity than perception, although it is less clear if this increased variability results in biases in color appearance 40 . In spite of this variability, a pronounced and consistent lag was observed in the Simple Matching Memory task (except in the koniocellular pathway in the blue to green direction), showing that adaptation mechanisms can be stored in visual memory. To explain preserved hysteresis under memory conditions, it has been demonstrated that prior knowledge helps maintain complex images in short-term memory 40 . In sum, our results show that the effect of hysteresis follows a negative lag in the memory task for the Green-Red cone contrast Channel, defining the parvocellular pathway, and the Blue-Yellow Channel (except in the Blue-Yellow trajectory) which cone contrast defines the Koniocellular pathway. Why there is not storage in the Blue-Yellow trajectory remains a question for future research. Visual binding was insensitive to the effects of adaptation, with the notable exception in the memory binding task in the yellow-blue channel. The observation that perceptual binding overrides adaptation mechanisms suggests that neural locus of perceptual binding is at a higher level than the one underlying adaptation and hysteresis, as compared to memory circuits. This suggests a suppressive top-down influence of binding mechanisms on adaptation which can be addressed in the future using fMRI. Top-down feedback might help shape sensory discrimination, especially when that input can elicit ambiguous or alternative perceptual interpretations, such as in this experiment. The feedback is thought to come from higher cortical areas that can re-enter lower cortical areas with additional information on global object configuration, and this interaction with lower visual areas would help disambiguate between the multiple perceptual possibilities 43 , as in predictive coding accounts. In this context, it is important to take into account that adaptation mechanisms, here revealed by negative hysteresis, are in general recognized to be present in earlier visual areas and, on the other hand, memory mechanisms featured by persistence and positive hysteresis, as well as binding of figural elements, may be identifiable at high-level regions 3 , 25 . This is a future testable hypothesis using neuroimaging. By showing various perceptual conditions in terms of color content and memory constraints, requiring or not feature integration, our study advances prior knowledge both regarding memory and binding effects and suggests a possible and plausible mechanistic difference across L-M (corresponding to parvocellular) and S-(L + M) (corresponding to koniocellular) pathways. The asymmetry of hysteresis identified in the koniocellular pathway maybe due to its physiological and anatomical physiological asymmetry, whereby ON Center blue (surround yellow) opponent bistratified ganglion cells are much more frequent than ON Center monostratified cells 44 . The attention feature binding hypothesis of Treisman 10 , is consistent with our results and would lead to the prediction of larger activation of parietal regions. We therefore predict that future neuroimaging studies should reveal activation of the right parietal region for the compound stimulus, requiring hard feature integration. As a limitation, the information provided by the subjective reference has the inherent limitation of being derived absent smooth transitions, but this was overcome by adding the veridical reference color, which replicated the analysis. We used an innovative hysteresis paradigm to demonstrate a winner-take-all dominance of adaptation versus visual persistence in specific color vision pathways, which can be stored in memory, and a two-stage mechanism for feature binding. Integration of local into global features, defining a hard binding problem, occurs independently of adaptation, regardless of whether it is visual or memory guided. These findings shed new light on binding theories, by excluding accounts based on long range synchrony starting in early visual cortex, and favouring feature integration theories. Methods Participants Twenty-two participants were recruited for this experiment (11 females and 11 males) with ages between 18 to 50 (See Supplementary Table 1 for details). Two were excluded due to the exclusion criteria defined for the neuropsychological tests (see below). This sample size is justified by a Power analysis based on effect sizes of our prior hysteresis work 1 , 5 . Assuming a needed power of 95% for and effect size of 1 (a conservative estimate) we would need a total sample size of 16. All had normal or corrected-to normal vision and preserved color vision as assessed by the Cambridge Color Test 45 . To test their short-term memory, visual perceptive function and attention, we performed a neuropsychology evaluation using the Kent Visual Perceptual Test – Memory (KVPT-M) 46 and D2 Test of Attention 47 respectively. Also, no history of neurological or other psychiatric diseases should be present as evaluated by the BSI – Brief Symptom Inventory 48 (furthermore, this was important because we planned to study this mechanism on some pathologies such as in Autism Spectrum Disorder). An exception was made if an anxiety disorder was present but it was controlled with psychotherapy and/or a small dose of medication with normal BSI scores. All participants gave prior informed written consent, in accordance with the declaration of Helsinki, and the work was approved by the Ethics Committee of the Faculty of Medicine of the University of Coimbra, Portugal. Full characterization of the group is provided in Supplementary Table 1. The mean age was 25.17 ± 3.98 years. For the Brief Symptom Inventory: BSI Positive Symptoms Average Index was 1.263 (cut off when \(\ge\) 1.7); BSI Subscale of Paranoid Ideation was 0.52 (cutoff when > 1.852); BSI Subscale of Psychoticism was 0.21 (cut off when > 1.282); D2 Concentration Index mean was 82.3 (following the norms for the age) and for the D2 Efficacy Index was 81.4 (following the norms for the age). Finally, in the Kent Visual Perceptual Test – Memory Test average scores were 20.35 for a maximum of 25. Stimuli We used a dynamic color matching paradigm (Figs. 2 and 3 ) with color excursions or trajectories along defined cone in cone space axes of L-M (Red-Green Channel) or S-(L + M) (Blue-Yellow channel). We characterized the monitor RGB channels using a spectroradiometer Apacer AL100/AL110 Spectroradiometer from Apacer Technology Inc. (Taiwan) in 18 points per channel and then calculated the fit parameters of the monitor's gamma function. Afterwards, we converted the values into the LMS isoluminant plane in cone-opponent color space 49 , 50 , with a color space converting function, and created an isoluminant conversion matrix. The Green-Red axis colors were obtained by manipulating S-(L + M) and the Blue-Yellow ones by manipulating L-M in the isoluminant plane (ensuring an average luminance level, 47 cd/m 2 ). The isoluminant colorsteps for each axis were converted back to RGB values using the colorspace function in MATLAB, gamma corrected with the calibrated monitor conversion matrix for display on the monitor. Isoluminant conditions were kept the same for all participants as confirmed luminance measures with the spectroradiometer, but as an additional measure we introduced luminance noise, which is a well known strategy, to prevent minor luminance deviations to bias the results 45 . Color stimulus trajectories were implemented in the M-L (Fig. 1 B) or S-(L + M) axes (Fig. 1 B), changing smoothly through color passing by a reference color (RC) for which target stimuli had to be matched and as such, the matching to this reference stimulus is inherently ambiguous. The size of stimulus and target was 2º of visual angle and the screen had a resolution of 1440 × 1080 pixels. For the testing trajectory conditions we ran 64 trials and for the control ones 32, divided in two runs. Each trial had either 8 (direct visual color match) or 9 (memory guided match) seconds, with a 1.5 second fixation cross before starting, so each run had between 5 and 6 minutes’ duration. Experimental setup and procedure The Psychtoolbox3 MATLAB toolbox (R2021B) was used to present stimuli for all tasks and to collect participants’ responses in combination with eyetracking recordings (Eyelink 1000 + SRResearch). Eye movements were analysed using Data Viewer software where we defined three areas of interest, Left, Center (fixation cross) and Right. In all experiments, the stimuli were presented on a liquid-crystal display (LCD; Display + + Cambridge Research Systems) monitor with a refresh rate of 100 Hz, and participants were comfortably seated at a distance of 70 cm from the display screen. Behavioural data were acquired during the perception of dynamic transitions between pairs of color endpoints in color space of either the green-red channel (Fig. 1 . B) or Blue-Yellow channel (Fig. 1 .B) to assessing the effects of temporal context. It was conducted under 8 distinct stimulus conditions counterbalanced in random order. Conditions one to four had a “Simple Stimulus” configuration (simple color matching with or without memory demands) and conditions five to eight had a “Compound Stimulus” which means that the main stimulus is a set of smaller elementary circles requiring holistic integration (perceptual binding: the circles with the same color are bound together into a single pattern – this is a purposefully hard binding condition). Experimental and Control Conditions can therefore be summarized as follows: Condition 1: Simple Stimulus Control (no stimulus history present); Condition 2: Simple Color Matching; Condition 3: Simple Memory Guided Color Matching Control; Condition 4: Simple Stimuli Memory Guided. Condition 5: Compound Stimuli Match Control; Condition 6: Compound Stimuli Color Matching; Condition 7: Compound Memory Guided Color Matching Control and 8: Compound Stimuli Memory Guided (Red-Green or Green-Blue). There were four groups in each condition that were counterbalanced: either is the stimulus on the Left or the Right side that changes and also either starts from one side of the color axis spectrum to the other or vice-versa. For all conditions the reference color (RC) is the color that subjects will have to match in all conditions and that is given either simultaneously with the other target or presented for only one second to be subsequently retrieved by memory. The target color (TC) is the color that is continuously changing and for which the subjects have to report the point of subjective equality. The background also had a medium luminance equal to the RC, mean of 47 cd/m 2 . Participants had to indicate by pressing the letter z if they thought the TC was the same as the RC and then when it immediately changed, by pressing the letter m . Control Conditions required matching the reference and target, which color was changing randomly along the defined axes in the spectrum. Participants had to report when the target matched the reference. Experimental conditions 2 and 6 were similar (using Simple and Compound Stimuli respectively) but the target was changing smoothly through the spectrum in a sequential order (Fig. 2 A and 3 A). Control Conditions 3 and 7, required memory matching in random order, as well as Conditions 4 and 8, which featured smooth transitions in a specific temporal order (Fig. 2 B and 3 B). Data processing and Statistical analysis The perceptual reports curves represent the gaussian fit (MATLAB Fit function) models to the real data points (Figs. 4 and 5 ). The fitted curves were calculated for each direction for both tasks, for Simple visual and memory guided Tasks, and were compared with both the real (veridical) reference color (RC) and the subject estimated point of subjective equality. A description of the metrics used and analyses performed is provided below. All statistical analyses were performed with SPSS Statistics V26. Data were tested for normality using the Shapiro-Wilk test with an α-level of 0.05 before running further statistical analyses. In order to analyse the significance of the hysteresis metric, the point of perceptual switch difference between the testing condition and the respective reference color and control for this, we used a paired-sample t-test using the colorstep values of the button press reporting the match. We used a significant p-value of .01. Metric of perceptual hysteresis Participants were required to identify the first and last timepoints in which they perceived the color to be same as the match either from memory or not. We analysed the first button press (reporting the match) in order to study the contribution of memory mechanisms (presence of persistence) to the perceptual decision on color matching. In each condition we used the mean response timepoint for each run (each participant had two runs) per color pathway (Blue-Yellow or Green-Red) and direction in color axis (forward or backward). The difference between the perceptual point of switch in the testing condition and the control condition was estimated as a metric of hysteresis. The control was separated for each cone contrast axis with no direction since the order of chromatic axis was random and the testing conditions were separated for each cone contrast type and each direction. Eyetracking Eyetracking was used to confirm that subjects maintained fixation on the stimuli. We considered the following metrics: average pupil size across all fixations in the area of interest, percentage of trial time spent on the current area of interest and duration of the first fixation event that was within the current area of interest. For statistical analysis, SPSS Statistics V26 was used and comparisons were made between the three AI (areas of interest) in each condition and also between conditions. Declarations Acknowledgments Funding: FCT/DSAIPA/DS/0041/2020, PTDC/PSI-GER/1326/2020-NeuroHyst, Hallucin - 2022.02963.PTDC, UIDB/4950/2020 and UIDP4950/2020 Authors Information: C. Matias 1 , João Castelhano 1 & Miguel Castelo-Branco 1,2 Affiliations 1 Institute for Nuclear Sciences Applied to Health, Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, 3000-548 Coimbra, Portugal 2 Department of Cognitive Neuroscience, University of Maastricht, The Netherlands Correspondence [email protected] Author Contributions F.C.M and M.C.B designed and conceived the experiments. J.C. programed the stimuli and the scripts of the data. F.C.M., MCB and JC designed analyses and FM performed the analysis and wrote the first draft. M.C.B. advised in analyses and interpretation. All authors revised the manuscript. Data availability statement Data will be made available upon reasonable request to the corresponding author Competing Interests Statement The authors have no competing interests to disclose. References Mullen, K. T., Chang, D. H. F. & Hess, R. F. 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(Oxford University Press, 2005). doi:10.1093/acprof:oso/9780198529699.001.0001. Shevell, S. The Science of Color: Second Edition . (2003). Pisarchik, A. N., Jaimes-Reátegui, R., Magallón-García, C. D. A. & Castillo-Morales, C. O. Critical slowing down and noise-induced intermittency in bistable perception: Bifurcation analysis. Biol. Cybern. 108 , 397–404 (2014). Schwiedrzik, C. M. et al. Untangling perceptual memory: Hysteresis and adaptation map into separate cortical networks. Cereb. Cortex 24 , 1152–1164 (2014). De Fez, M. D., Capilla, P., Luque, M. J., Pérez-Carpinell, J. & Del Pozo, J. C. Asymmetric colour matching: Memory matching versus simultaneous matching. Color Res. Appl. 26 , 458–468 (2001). Olkkonen, M. & Allred, S. R. Short-term memory affects color perception in context. PLoS One 9 , 1–11 (2014). Ling, Y. & Hurlbert, A. Role of color memory in successive color constancy: erratum. J. Opt. Soc. Am. A 26 , 1544 (2009). Jin, E. W. & Shevell, S. K. Color memory and color constancy. J. Opt. Soc. Am. A 13 , 1981 (1996). Bi, K., Zhang, Y. & Zhang, Y. Y. Central-peripheral dichotomy: color-motion and luminance-motion binding show stronger top-down feedback in central vision. Attention, Perception, Psychophys. 84 , 861–877 (2022). Dacey, D. & Lee, B. The ‘blue-on’ opponent pathways in primate retina originates from a distinct bistratified ganglion cell. Nature 367 , 731–735 (1994). Mollon, J. D. & Regan, B. C. Cambridge Colour Test Handbook . (Cambridge Research Systems, 2000). Melamed, L. E. Kent Visual Perceptual Test: Professional Manual . (Psychological Assessment Resources, Inc., 2000). Brickenkamp, R. Teste de Atenção: Manual d2 . (CEGOG-TEA, 2007). Canavarro, M. C. Inventário de Sintomas Psicopatológicos: BSI. in Testes e provas psicológicas em Portugal (eds. Simões, M. R., Gonçalves, M. & Almeida, L. S.) vol. II, 87-109 (SHO/APPORT, 1999). MacLeod, D. I. A. & Boynton, R. M. Chromaticity diagram showing cone excitation by stimuli of equal luminance. J. Opt. Soc. Am. 69 , 1183 (1979). Derrington, A. M. & Lennie, P. Spatial and temporal contrast sensitivities of neurones in lateral geniculate nucleus of macaque. J. Physiol. 357 , 219–240 (1984). Additional Declarations No competing interests reported. Supplementary Files SupplementaryDataandTables.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3301293","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":229845476,"identity":"bbd2c77a-758c-4a21-950f-5f9ca74c0aec","order_by":0,"name":"Francisca C. Matias","email":"","orcid":"","institution":"University of Coimbra","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Francisca","middleName":"C.","lastName":"Matias","suffix":""},{"id":229845477,"identity":"e806d6e3-29b6-4790-8ac4-c0d25313a7b0","order_by":1,"name":"João Castelhano","email":"","orcid":"","institution":"University of Coimbra","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"João","middleName":"","lastName":"Castelhano","suffix":""},{"id":229845478,"identity":"efc2b349-4491-44f7-affd-5f165f692417","order_by":2,"name":"Miguel Castelo-Branco","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYFACHgjFz3wAziZSi2RbAozNTKQWg2PEatFtP3vsw88ddnLGx7gTH7xhOCzPIN1/AK8WszN5yTN7zyQbmx3j3Ww4h+GwYYPMYfy2mN3gMWbgbTuQuO1+7zZpHobDCQwSyYS1MP4Fatncxrv9N9FamEG2bGDj3cZMnBagX5hl25KNJYB+kZxjkG7YJnPYAL+W42cPM75ts5Pjb+Pd+OFNhbU8v3TjA/zWoAKg+WwSpGiAADK0jIJRMApGwfAGANYIP9jmCOGTAAAAAElFTkSuQmCC","orcid":"","institution":"University of Coimbra","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Miguel","middleName":"","lastName":"Castelo-Branco","suffix":""}],"badges":[],"createdAt":"2023-08-27 21:59:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3301293/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3301293/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":42501266,"identity":"e94b59d8-f2a7-460f-941a-ddf7af55a93c","added_by":"auto","created_at":"2023-09-01 14:45:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":324207,"visible":true,"origin":"","legend":"\u003cp\u003eA.\u0026nbsp; Hysteresis in the perceptual domain. Orange: control curve (no influence of stimulus history). A shift to the left (negative lag) corresponds to negative hysteresis and to the right to positive hysteresis (positive lag). Blue: actual perceptual curves (left: early perceptual shift corresponding to negative hysteresis and adaptation; right: late perceptual shift corresponding to positive hysteresis and persistence B. Representation of the color axes used in the task, in DKL (Derrington-Krauskopf-Lennie) space\u003csup\u003e24\u003c/sup\u003e, in which the coordinates represent the purported responses of orthogonal contrast discrimination mechanism, L+M, L–M, and S–(L+M). We used the Red-green (L-M) opponent contrast Channel (related to the parvocellular pathway); and the Blue-Yellow opponent contrast Channel (S–(L+M), related to of the koniocellular channel) distributed over the isoluminant plane.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/ff05b1810b3850f8faf72683.png"},{"id":42501267,"identity":"34f24dfc-37be-4473-85db-63f1f999cfa3","added_by":"auto","created_at":"2023-09-01 14:45:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1026096,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/dfc7825415bc3cbc39fb89f7.png"},{"id":42501830,"identity":"9dd70c9c-f59a-462c-8e4e-e3c8de1c95cd","added_by":"auto","created_at":"2023-09-01 14:53:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1021197,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/e43bbd2cb7ce18d6ce2795b5.png"},{"id":42501271,"identity":"9f4df944-27c6-4ed5-bb77-4a1e3022992c","added_by":"auto","created_at":"2023-09-01 14:45:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":161912,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePerceptual Negative hysteresis in simple color matching tasks. Please note that color matching peaks occur earlier (negative lags) than for the control condition without stimulus history. \u003c/strong\u003eFigure panels summarize the group average results for the dynamic transitions (button presses) of cone contrast Green-Red (A1) and Blue-Yellow (A2) axes for the simple match task and Simple memory guided matching task (B1 and B2). The average transition colors are represented for both directions (M-L, e.g Green-Red: direction 1: green line; direction 2: red line; (S_(L+M) eg, Blue-Yellow: direction 1: blue line; direction 2: green line) and the respective real reference interval (RC) is plotted as a black curve for sake of visual comparison. Results are normalized to the maximum number of perceptual transitions at a specific color step. Perceptual switch differences between the two directions and the RC are statistically significant as detailed above. The * symbol depicts statistical significance of \u0026lt;.001.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/be74a0ec87f07f97c6c83cbb.png"},{"id":42501270,"identity":"2f09fc90-357e-4b2c-b1ed-9156acb2911d","added_by":"auto","created_at":"2023-09-01 14:45:03","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":821744,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eNegative hysteresis is largely absent in color matching tasks requiring binding\u003c/strong\u003e. \u0026nbsp;\u003cstrong\u003ePlease note that color matching peaks occur nearly at the same position compared to the control condition without stimulus history. \u003c/strong\u003eFigure panels summarize the group average results for the dynamic transitions (button presses) of cone contrast M-L Green-Red (A1) and S-(L+M) Blue-Yellow (A2) for the simple match task and Simple memory task (B1 and B2). The average transition colors are represented for both directions (Green-Red: direction 1: green line; direction 2: red line; (Blue-Yellow: direction 1:blue line; direction 2: green line) and the respective real reference interval is plotted as a black curve for sake of visual comparison. Results are normalized to the maximum number of transitions at a specific color step. . The * symbol depicts statistical significance of \u0026lt;.001.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/cb1f8e9a5f53816041dca3e5.png"},{"id":48031132,"identity":"be189e93-2b5b-4f4c-8280-25b14dcdbf87","added_by":"auto","created_at":"2023-12-12 06:07:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1577671,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/436348ed-7120-4a8a-be02-a16cfafe60f5.pdf"},{"id":42501269,"identity":"f6884288-304b-4b4a-a8a2-ac309d6f3365","added_by":"auto","created_at":"2023-09-01 14:45:03","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":21740,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryDataandTables.docx","url":"https://assets-eu.researchsquare.com/files/rs-3301293/v1/3e596d863d4207deaeb25841.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Perceptual binding occurs independently beyond early neural adaptation stages in human color cone pathways","fulltext":[{"header":"Introduction","content":"\u003cp\u003eQuantitative studies of the dynamics of perception are important to investigate its dependence on history and context1\u003csup\u003e1\u0026ndash;3\u003c/sup\u003e. Perceptual decision if often difficult because of the inherently ambiguous choice between distinct interpretations of the sensory world which can be influenced by factors such as attention, prior probability of the occurrence of an event and previous outcomes\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA related important question is whether holistic integration under ambiguous sensory contexts and gestalt perceptual formation occur at early visual levels \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. It is known that perceptual decisions are controlled by high level, integrative top-down factors, like prior knowledge and bottom-up factors that reflect sensory input \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The binding problem of how visual processing leads to merging local elements them into a global holistic representation remains strongly debated. This problem refers to the scientific challenge of identifying mechanisms that may achieve the integration of local elements into global percepts \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Although mechanisms for local contextual processing are well-known to occur at early visual levels\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, the neural locus of global binding remains elusive. Several theories have been raised to explain perceptual binding, namely the feature integration theory, which postulates that it is a separable high level process, where attention serves as a mechanistic \u0026ldquo;glue\u0026rdquo; for visual binding \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. An alternative account postulates that binding is instantiated at early visual levels, by a binding by synchrony mechanism\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u0026acute;\u003c/p\u003e \u003cp\u003eColour adaptation can be used as a tool to address this question because it occurs within early visual pathways up to V4, which are involved in local scene analysis\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Therefore if the neural locus binding occurs at these early levels, it should be sensitive to adaptation mechanisms. These mechanisms can be tested by the study of adaptation along chromatic pathways defined in cone contrast space.\u003c/p\u003e \u003cp\u003eThe LMS color space, also known as the cone-opponent color space, is a color model based on the responses of the three types of cones in the human visual system: the long-wavelength (L)(red) cones, the medium-wavelength (M)(green) cones, and the short-wavelength (S)(blue) cones. These cones are responsible for detecting different ranges of light wavelengths \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. It is widely used in color vision research and provides a valuable tool for understanding color perception and visual processing, since it can be used to analyse and manipulate color stimuli based on the specific responses along given chromatic axes corresponding to specific pathways\u003csup\u003e\u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. It is however important in such experiments to not deviate from the isoluminant plane and to take measures to prevent the use of non chromatic cues.\u003c/p\u003e \u003cp\u003eAs stated above adaptation occurs from the retinal processing to early visual processing levels, and can be described as a phenomenon where prolonged exposure to a specific sensory stimulus leads to changes in neural responses, ultimately impacting perception\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Adaptation effects have been observed in specific visual features, including orientation, motion direction, spatial frequency, and face identity.\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePerceptual binding refers to the process by which the brain combines various visual features, such as color, shape, motion, and texture, into a unified and coherent perception of objects and scenes\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. It remains an open question whether binding reflects an hierarchical, involving process multiple stages of information processing in the visual system\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, or instead it is instantiated in widespread neural assemblies\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. At the initial stages of visual processing, basic features, such as color and orientation, are extracted by specialized cells in the primary visual cortex (V1)\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. These features are represented in separate neural channels or feature maps. Integration of visual information occurs through reciprocal connections and feedback mechanisms\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. According to this view, the hierarchical nature of visual processing allows for the integration of increasingly complex information, leading to the formation of meaningful and coherent representations of the visual world\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. This view is consistent with feature integration theory, but an alternative mechanism is binding by synchronization, and this research question remains highly debated.\u003c/p\u003e \u003cp\u003eOne way to answer the research question whether binding occurs at processing level immune to low level processing mechanisms is to probe it with early level physiological adaptation. Adaptation is one mechanism contributing to phenomena such as hysteresis. Positive and negative hysteresis are well known phenomena in the physical, biological and psychological sciences\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e(Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The former occurs when the change in perceptual switching is delayed (positive lag, corresponding to a sort of short-term memory or persistence. Negative hysteresis reflects the opposing phenomenon of adaptation/fatigue leading to earlier perceptual switches than predicted in the absence of stimulus history (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The corresponding early transitions (negative lags) have therefore a hallmark of adaptation/habituation mechanisms\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The study of hysteresis therefore innovatively links two very important neural processes, neural fatigue and short-term memory, and opens windows into understanding their relation with perceptual integration and visual binding. To provide generalization, we tested this hypothesis under visually or memory-guided conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOur first research question was whether positive or negative hysteresis occur in color processing pathways. Previous studies in other perceptual domains used paradigms such as letter recognition\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e, emotion recognition\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, binocular rivalry \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e, motion \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. In most cases positive hysteresis tended to dominate. Here we aimed to understand the dominant outcome of the competition between adaptation and visual persistence in color pathways. Our study directly compared competition between these mechanisms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe central question was however to understand whether perceptual binding, defined as the holistic integration of global patterns based on local elements (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), is sensitive to the effects of adaptation. If this were not the case, then this would imply that its neural locus is at a higher stage.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn sum, we manipulated color along axes (L-M and S-(L\u0026thinsp;+\u0026thinsp;M) cone contrast space related to parvo and koniocellular pathways, respectively, to address the following research questions: If hysteresis occurs in dynamic color matching trajectories does adaptation, as indexed by negative hysteresis, dominate instead of visual persistence (indexed by positive hysteresis)? Is perceptual binding a unaffected by visual adaptation under visual and memory guided matching? If this is the case, this would place the neural underpinnings of binding at a level beyond early visual processing where perceptual and memory representations converge, consistent with the feature integration theory, whereby bound object/surface representations processed at a stage beyond sensory feature processing.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eFor analysis if hysteresis for all color trajectory conditions, we determined the ordinal point positions where a dynamic color match occurred. Before that, we first established the relation between the static matching point of subjective equality and veridical physical reference (corresponding to a veridical, non-subjective, true physical match). Subjective equality of a static target to the reference color was determined by the control perceptual matching experiments, in the absence of dynamic color changes, and was found to be statistical similar to the (veridical) Reference Color (RC) of the control condition. This demonstrates that there was no significant difference between the point of subjective equality and veridical physical reference.\u003c/p\u003e \u003cp\u003eWe found significant negative perceptual hysteresis in the Simple Color Matching experiments for both cone contrast channels and directions (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, Top panels; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for all t tests comparing perceptual curves along Green-Red and Blue-Yellow axes in both directions with Veridical Reference Color; t values ranged from \u0026minus;\u0026thinsp;4,4 to \u0026ndash; 5,8). These effects were replicated when using the subjectively determined neutral midpoint instead of the veridical reference color (RC) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eResults are depicted in full tabular form in supplementary Tables\u0026nbsp;2 and 3. Negative hysteresis was also replicated for Simple Memory Guided task (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, Bottom panels, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, t ranging from \u0026minus;\u0026thinsp;6,6 to -7,7) except for the Blue-Yellow direction, where the effect was marginal (t = -1,968; p\u0026thinsp;=\u0026thinsp;.064).\u003c/p\u003e \u003cp\u003eConcerning stimuli requiring holistic binding, hysteresis vanished regardless of using veridical or a reference point of subjective equality, for visually guided binding (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, top panels). The same held true for memory guided binding (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, bottom panels), with the notable exception of the yellow-blue channel (t = -5.273; p\u0026thinsp;\u0026lt;\u0026thinsp;.001; t = -3.389; p\u0026thinsp;=\u0026thinsp;0.003; Veridical Reference Color, Perceived Reference Control Curve, respectively).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn sum, we observed significant negative hysteresis both in visually guided and Simple Match from Memory experiment for the M-L parvocellular related pathway (Green-Red cone contrast Channel) in both directions and the koniocellular pathway with the exception of the Blue-Yellow direction in the memory task. Remarkably, when the task required perceptual binding hysteresis was virtually absent with the single notable exception of the Direction Blue to Blue in the Memory task (for full statistics, See Supplementary Tables\u0026nbsp;2 and 3 and for visualization of effects sees Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study we found that color perception is characterized by strong negative hysteresis, unlike other perceptual domains like motion perception or emotion recognition, where positive hysteresis dominates. This observation occurred specifically for simple and memory-based color matching tasks. Regarding our core research question, the effects of adaptation were not present when perceptual binding was required, regardless of whether it was visually or memory-guided. Taken together, these observations demonstrate that the locus of perceptual binding is beyond early visual processing.\u003c/p\u003e \u003cp\u003eWe took advantage of the phenomenon of hysteresis to quantify the impact of adaptation. This allowed to dissect mechanisms underlying the relative role of sensory/low level processes and visual persistence memory mechanisms and in particular if perceptual binding is changed by low level adaptation. Our color matching hysteresis based paradigm allowed to show that adaptation is a winning mechanism when competing versus visual persistence in terms of temporal context. The independence from adaptation shows that binding is a separable high level process, which is consistent with the feature integration theory (FIT) theory postulated by Treisman and Gelade that stated that binding occurs at higher levels, when attention is needed for the integration to occur\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo ensure that we could isolate chromatic pathways, the mechanisms underpinning perceptual hysteresis were investigated by manipulating trajectories in cone contrast space (L-M and S-(L\u0026thinsp;+\u0026thinsp;M) channels). We first aimed to determine which mechanism, persistence or adaptation, dominated in perception as indexed by signatures of positive and negative hysteresis, respectively \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Regarding visual perceptual hysteresis, prior work suggested dominance of positive hysteresis in most visual domains \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. This is to our knowledge the first study of hysteresis on color perception, and we found that negative hysteresis dominated in this case and that binding overruled this mechanism. This provides evidence that temporal effects in perception are dependent on the level of visual processing. Accordingly, the comparison of hysteresis effects in color matching requiring or not perceptual binding (necessary for the hard integration of compound stimuli) shows that they only occur for simple low level tasks at neural locus of adaptation. When binding is required it show to be independent to adaptation properties in low level vision, regardless of whether feature integration is visually or memory guided. This places this type of visual integration process at a second stage of visual processing, as predicted by the attention feature binding hypothesis of Treisman\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIt is important to point out that hysteresis features a form of study of serial dependence and it was therefore important to avoid in our stimulus presentation the presence of color aftereffects in which prolonged exposure to a particular color stimulus leads to a temporary shift to the perception of complementary colors.\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e This is in fact demonstrates the existence of opponent channels such as the ones studied here, because the underlying mechanisms is also neural in color-sensitive neurons\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. Our participants never reported the presence of color aftereffects and that could not possibly be happening since the exposure to a given stimulus was very short within a stimulis stream color aftereffects require prolonged exposure to a specific color stimulus \u003csup\u003e\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eRegarding the simple matching conditions, negative hysteresis was discovered both in direct Color Matching and Memory conditions, for both cardinal channels of color vision, which is consistent with the notion that adaptation can be stored in memory, with the single exception for the memory task in blue to green transitions. When moving from the source color passing through the veridical physical reference (true reference color), the perceptual flip happened similarly in both directions, yet prior to the appearance of the true reference (lag\u0026thinsp;\u0026lt;\u0026thinsp;0, characteristic of negative hysteresis). In the same line, and as a replication analysis, when compared to the subjective reference as measured using the control experiments (reference measured experimentally with the absence of stimulus history), the same results were found. The identification of such robust negative hysteresis is quite interesting and a surprising outcome since the most widely investigated hysteresis phenomena in the realm of visual perception are characterized by a positive hysteresis lag signature\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e or a balanced competition of both adaptation and persistence \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e whilst here we identified a strong effect for adaptation (a winner-take-all mechanisms against visual persistence). This shows that when matching the color visually or in a memory-guided manner, participants report a change earlier than expected in absence of history.\u003c/p\u003e \u003cp\u003eConcerning color, there are no studies with hysteresis, which is a very different phenomenon when compared with earlier studies on short term color memory \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan additionalcitationids=\"CR40 CR41\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. When there is a delay in time between reference and matching stimuli, memory allocation or successive matching occurs\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. There are often differences between the original and the memory-matched color, usually represented by hue, brightness and saturation shifts of the matched stimulus even if the luminance stays the same\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. The literature points out that color memory tends to emphasize the chromatic attributes, mostly by saturation and lightness increases \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. Color memory is expectedly more variable in fidelity than perception, although it is less clear if this increased variability results in biases in color appearance\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. In spite of this variability, a pronounced and consistent lag was observed in the Simple Matching Memory task (except in the koniocellular pathway in the blue to green direction), showing that adaptation mechanisms can be stored in visual memory. To explain preserved hysteresis under memory conditions, it has been demonstrated that prior knowledge helps maintain complex images in short-term memory \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. In sum, our results show that the effect of hysteresis follows a negative lag in the memory task for the Green-Red cone contrast Channel, defining the parvocellular pathway, and the Blue-Yellow Channel (except in the Blue-Yellow trajectory) which cone contrast defines the Koniocellular pathway. Why there is not storage in the Blue-Yellow trajectory remains a question for future research.\u003c/p\u003e \u003cp\u003eVisual binding was insensitive to the effects of adaptation, with the notable exception in the memory binding task in the yellow-blue channel. The observation that perceptual binding overrides adaptation mechanisms suggests that neural locus of perceptual binding is at a higher level than the one underlying adaptation and hysteresis, as compared to memory circuits. This suggests a suppressive top-down influence of binding mechanisms on adaptation which can be addressed in the future using fMRI. Top-down feedback might help shape sensory discrimination, especially when that input can elicit ambiguous or alternative perceptual interpretations, such as in this experiment. The feedback is thought to come from higher cortical areas that can re-enter lower cortical areas with additional information on global object configuration, and this interaction with lower visual areas would help disambiguate between the multiple perceptual possibilities\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e, as in predictive coding accounts. In this context, it is important to take into account that adaptation mechanisms, here revealed by negative hysteresis, are in general recognized to be present in earlier visual areas and, on the other hand, memory mechanisms featured by persistence and positive hysteresis, as well as binding of figural elements, may be identifiable at high-level regions\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. This is a future testable hypothesis using neuroimaging.\u003c/p\u003e \u003cp\u003eBy showing various perceptual conditions in terms of color content and memory constraints, requiring or not feature integration, our study advances prior knowledge both regarding memory and binding effects and suggests a possible and plausible mechanistic difference across L-M (corresponding to parvocellular) and S-(L\u0026thinsp;+\u0026thinsp;M) (corresponding to koniocellular) pathways. The asymmetry of hysteresis identified in the koniocellular pathway maybe due to its physiological and anatomical physiological asymmetry, whereby ON Center blue (surround yellow) opponent bistratified ganglion cells are much more frequent than ON Center monostratified cells \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. The attention feature binding hypothesis of Treisman\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, is consistent with our results and would lead to the prediction of larger activation of parietal regions. We therefore predict that future neuroimaging studies should reveal activation of the right parietal region for the compound stimulus, requiring hard feature integration.\u003c/p\u003e \u003cp\u003eAs a limitation, the information provided by the subjective reference has the inherent limitation of being derived absent smooth transitions, but this was overcome by adding the veridical reference color, which replicated the analysis.\u003c/p\u003e \u003cp\u003eWe used an innovative hysteresis paradigm to demonstrate a winner-take-all dominance of adaptation versus visual persistence in specific color vision pathways, which can be stored in memory, and a two-stage mechanism for feature binding. Integration of local into global features, defining a hard binding problem, occurs independently of adaptation, regardless of whether it is visual or memory guided. These findings shed new light on binding theories, by excluding accounts based on long range synchrony starting in early visual cortex, and favouring feature integration theories.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eParticipants\u003c/p\u003e \u003cp\u003eTwenty-two participants were recruited for this experiment (11 females and 11 males) with ages between 18 to 50 (See Supplementary Table\u0026nbsp;1 for details). Two were excluded due to the exclusion criteria defined for the neuropsychological tests (see below). This sample size is justified by a Power analysis based on effect sizes of our prior hysteresis work\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Assuming a needed power of 95% for and effect size of 1 (a conservative estimate) we would need a total sample size of 16. All had normal or corrected-to normal vision and preserved color vision as assessed by the Cambridge Color Test\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. To test their short-term memory, visual perceptive function and attention, we performed a neuropsychology evaluation using the Kent Visual Perceptual Test \u0026ndash; Memory (KVPT-M)\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e and D2 Test of Attention\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e respectively. Also, no history of neurological or other psychiatric diseases should be present as evaluated by the BSI \u0026ndash; Brief Symptom Inventory\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e (furthermore, this was important because we planned to study this mechanism on some pathologies such as in Autism Spectrum Disorder). An exception was made if an anxiety disorder was present but it was controlled with psychotherapy and/or a small dose of medication with normal BSI scores. All participants gave prior informed written consent, in accordance with the declaration of Helsinki, and the work was approved by the Ethics Committee of the Faculty of Medicine of the University of Coimbra, Portugal.\u003c/p\u003e \u003cp\u003eFull characterization of the group is provided in Supplementary Table\u0026nbsp;1. The mean age was 25.17\u0026thinsp;\u0026plusmn;\u0026thinsp;3.98 years. For the Brief Symptom Inventory: BSI Positive Symptoms Average Index was 1.263 (cut off when \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\ge\\)\u003c/span\u003e\u003c/span\u003e1.7); BSI Subscale of Paranoid Ideation was 0.52 (cutoff when \u0026gt;\u0026thinsp;1.852); BSI Subscale of Psychoticism was 0.21 (cut off when \u0026gt;\u0026thinsp;1.282); D2 Concentration Index mean was 82.3 (following the norms for the age) and for the D2 Efficacy Index was 81.4 (following the norms for the age). Finally, in the Kent Visual Perceptual Test \u0026ndash; Memory Test average scores were 20.35 for a maximum of 25.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStimuli\u003c/h2\u003e \u003cp\u003eWe used a dynamic color matching paradigm (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) with color excursions or trajectories along defined cone in cone space axes of L-M (Red-Green Channel) or S-(L\u0026thinsp;+\u0026thinsp;M) (Blue-Yellow channel). We characterized the monitor RGB channels using a spectroradiometer Apacer AL100/AL110 Spectroradiometer from Apacer Technology Inc. (Taiwan) in 18 points per channel and then calculated the fit parameters of the monitor's gamma function. Afterwards, we converted the values into the LMS isoluminant plane in cone-opponent color space\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e,\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, with a color space converting function, and created an isoluminant conversion matrix. The Green-Red axis colors were obtained by manipulating S-(L\u0026thinsp;+\u0026thinsp;M) and the Blue-Yellow ones by manipulating L-M in the isoluminant plane (ensuring an average luminance level, 47 cd/m\u003csup\u003e2\u003c/sup\u003e). The isoluminant colorsteps for each axis were converted back to RGB values using the colorspace function in MATLAB, gamma corrected with the calibrated monitor conversion matrix for display on the monitor. Isoluminant conditions were kept the same for all participants as confirmed luminance measures with the spectroradiometer, but as an additional measure we introduced luminance noise, which is a well known strategy, to prevent minor luminance deviations to bias the results\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eColor stimulus trajectories were implemented in the M-L (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB) or S-(L\u0026thinsp;+\u0026thinsp;M) axes (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB), changing smoothly through color passing by a reference color (RC) for which target stimuli had to be matched and as such, the matching to this reference stimulus is inherently ambiguous. The size of stimulus and target was 2\u0026ordm; of visual angle and the screen had a resolution of 1440 \u0026times; 1080 pixels. For the testing trajectory conditions we ran 64 trials and for the control ones 32, divided in two runs. Each trial had either 8 (direct visual color match) or 9 (memory guided match) seconds, with a 1.5 second fixation cross before starting, so each run had between 5 and 6 minutes\u0026rsquo; duration.\u003c/p\u003e \u003cp\u003eExperimental setup and procedure\u003c/p\u003e \u003cp\u003eThe Psychtoolbox3 MATLAB toolbox (R2021B) was used to present stimuli for all tasks and to collect participants\u0026rsquo; responses in combination with eyetracking recordings (Eyelink 1000\u0026thinsp;+\u0026thinsp;SRResearch). Eye movements were analysed using Data Viewer software where we defined three areas of interest, Left, Center (fixation cross) and Right. In all experiments, the stimuli were presented on a liquid-crystal display (LCD; Display\u0026thinsp;+\u0026thinsp;+\u0026thinsp;Cambridge Research Systems) monitor with a refresh rate of 100 Hz, and participants were comfortably seated at a distance of 70 cm from the display screen.\u003c/p\u003e \u003cp\u003eBehavioural data were acquired during the perception of dynamic transitions between pairs of color endpoints in color space of either the green-red channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. B) or Blue-Yellow channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.B) to assessing the effects of temporal context. It was conducted under 8 distinct stimulus conditions counterbalanced in random order. Conditions one to four had a \u0026ldquo;Simple Stimulus\u0026rdquo; configuration (simple color matching with or without memory demands) and conditions five to eight had a \u0026ldquo;Compound Stimulus\u0026rdquo; which means that the main stimulus is a set of smaller elementary circles requiring holistic integration (perceptual binding: the circles with the same color are bound together into a single pattern \u0026ndash; this is a purposefully hard binding condition). Experimental and Control Conditions can therefore be summarized as follows: Condition 1: Simple Stimulus Control (no stimulus history present); Condition 2: Simple Color Matching; Condition 3: Simple Memory Guided Color Matching Control; Condition 4: Simple Stimuli Memory Guided. Condition 5: Compound Stimuli Match Control; Condition 6: Compound Stimuli Color Matching; Condition 7: Compound Memory Guided Color Matching Control and 8: Compound Stimuli Memory Guided (Red-Green or Green-Blue). There were four groups in each condition that were counterbalanced: either is the stimulus on the Left or the Right side that changes and also either starts from one side of the color axis spectrum to the other or vice-versa.\u003c/p\u003e \u003cp\u003eFor all conditions the reference color (RC) is the color that subjects will have to match in all conditions and that is given either simultaneously with the other target or presented for only one second to be subsequently retrieved by memory. The target color (TC) is the color that is continuously changing and for which the subjects have to report the point of subjective equality. The background also had a medium luminance equal to the RC, mean of 47 cd/m\u003csup\u003e2\u003c/sup\u003e. Participants had to indicate by pressing the letter \u003cb\u003ez\u003c/b\u003e if they thought the TC was the same as the RC and then when it immediately changed, by pressing the letter \u003cb\u003em\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eControl Conditions required matching the reference and target, which color was changing randomly along the defined axes in the spectrum. Participants had to report when the target matched the reference. Experimental conditions 2 and 6 were similar (using Simple and Compound Stimuli respectively) but the target was changing smoothly through the spectrum in a sequential order (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Control Conditions 3 and 7, required memory matching in random order, as well as Conditions 4 and 8, which featured smooth transitions in a specific temporal order (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eData processing and Statistical analysis\u003c/p\u003e \u003cp\u003eThe perceptual reports curves represent the gaussian fit (MATLAB Fit function) models to the real data points (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The fitted curves were calculated for each direction for both tasks, for Simple visual and memory guided Tasks, and were compared with both the real (veridical) reference color (RC) and the subject estimated point of subjective equality. A description of the metrics used and analyses performed is provided below.\u003c/p\u003e \u003cp\u003eAll statistical analyses were performed with SPSS Statistics V26. Data were tested for normality using the Shapiro-Wilk test with an α-level of 0.05 before running further statistical analyses. In order to analyse the significance of the hysteresis metric, the point of perceptual switch difference between the testing condition and the respective reference color and control for this, we used a paired-sample t-test using the colorstep values of the button press reporting the match. We used a significant p-value of .01.\u003c/p\u003e \u003cp\u003eMetric of perceptual hysteresis\u003c/p\u003e \u003cp\u003eParticipants were required to identify the first and last timepoints in which they perceived the color to be same as the match either from memory or not. We analysed the first button press (reporting the match) in order to study the contribution of memory mechanisms (presence of persistence) to the perceptual decision on color matching. In each condition we used the mean response timepoint for each run (each participant had two runs) per color pathway (Blue-Yellow or Green-Red) and direction in color axis (forward or backward). The difference between the perceptual point of switch in the testing condition and the control condition was estimated as a metric of hysteresis. The control was separated for each cone contrast axis with no direction since the order of chromatic axis was random and the testing conditions were separated for each cone contrast type and each direction.\u003c/p\u003e \u003cp\u003eEyetracking\u003c/p\u003e \u003cp\u003eEyetracking was used to confirm that subjects maintained fixation on the stimuli. We considered the following metrics: average pupil size across all fixations in the area of interest, percentage of trial time spent on the current area of interest and duration of the first fixation event that was within the current area of interest. For statistical analysis, SPSS Statistics V26 was used and comparisons were made between the three AI (areas of interest) in each condition and also between conditions.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e FCT/DSAIPA/DS/0041/2020, PTDC/PSI-GER/1326/2020-NeuroHyst, Hallucin - 2022.02963.PTDC, UIDB/4950/2020 and UIDP4950/2020\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAuthors Information:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eC. Matias\u003csup\u003e1\u003c/sup\u003e, Jo\u0026atilde;o Castelhano\u003csup\u003e1\u003c/sup\u003e \u0026amp; Miguel Castelo-Branco\u003csup\u003e1,2\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAffiliations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eInstitute for Nuclear Sciences Applied to Health, Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, 3000-548 Coimbra, Portugal\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u003c/sup\u003eDepartment of Cognitive Neuroscience, University of Maastricht, The Netherlands\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence\u003c/strong\u003e\u003c/p\u003e\n\u003cp\[email protected]\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eF.C.M and M.C.B designed and conceived the experiments. J.C. programed the stimuli and the scripts of the data. F.C.M., MCB and JC designed analyses and FM performed the analysis and wrote the first draft. M.C.B. advised in analyses and interpretation. All authors revised the manuscript.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eData availability statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available upon reasonable request to the corresponding author\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eCompeting Interests Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no competing interests to disclose.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMullen, K. T., Chang, D. H. F. \u0026amp; Hess, R. F. The selectivity of responses to red‐green colour and achromatic contrast in the human visual cortex: an fMRI adaptation study. \u003cem\u003eEur. J. 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Physiol.\u003c/em\u003e \u003cstrong\u003e357\u003c/strong\u003e, 219\u0026ndash;240 (1984).\u003c/li\u003e\n\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-3301293/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3301293/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eColor perception entails competing temporal context mechanisms such as adaptation versus memory persistence\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Perceptual dynamics in color cone pathways can be studied using the phenomenon of hysteresis, well-known in the framework of physical dynamical systems. It postulates analogous mechanisms: a) visual persistence defining positive hysteresis b) adaptation or habituation (negative hysteresis). Adaptation causes early perceptual switches to competing states. We investigated competition between these mechanisms in human color cone pathways. Color adaptation occurs within early visual pathways up to V4, involved in local scene analysis, but it is unknown if they underlie global perceptual binding of visual elements\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. We tested if the neural locus of perceptual binding occurs at visual and memory stages beyond the locus of color adaptation, using a dynamic color matching task in cone contrast space, along Blue-Yellow (S-(L\u0026thinsp;+\u0026thinsp;M) and Green-Red processing channels (L-M). Simple vs Compound stimuli required or not holistic perceptual binding, under visual or memory-guided conditions. Adaptation (negative hysteresis) dominated for the former condition, was stored in memory, but vanished when binding was required either in vision or memory. In sum, cone pathway adaptation mechanisms dominate in early vision, while perceptual binding occurs at a second stage as predicted by the feature integration theory.\u003c/p\u003e","manuscriptTitle":"Perceptual binding occurs independently beyond early neural adaptation stages in human color cone pathways","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-09-01 14:44:58","doi":"10.21203/rs.3.rs-3301293/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":"dad37f99-88df-4496-a920-169eeb66879f","owner":[],"postedDate":"September 1st, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-12-12T05:53:02+00:00","versionOfRecord":[],"versionCreatedAt":"2023-09-01 14:44:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3301293","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3301293","identity":"rs-3301293","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}