{"paper_id":"0bad1ed8-c2b9-4c0c-ba6c-a42eb0294d44","body_text":"1 \n 1 \n 2 \nA transient signal in foveal superior colliculus neurons for 3 \njumpstar4ng peripheral saccadic orien4ng 4 \n 5 \n 6 \nTong Zhang1, 2*, Anna F. Denninger1,2,3*, Ziad M. Hafed1, 2 7 \n 8 \n1  Werner Reichardt Centre for IntegraDve Neuroscience, University of Tübingen, Tübingen, 9 \nGermany 10 \n2  HerDe InsDtute for Clinical Brain Research, University of Tübingen, Tübingen, Germany 11 \n3 Department of Psychiatry and Psychotherapy, Center for Mental Health (TüCMH), 12 \nUniversity of Tübingen, Tübingen, Germany 13 \n 14 \n 15 \n 16 \n* Contributed equally 17 \n 18 \n 19 \nCorrespondence: ziad.m.hafed@cin.uni-tuebingen.de  20 \n 21 \n 22 \n 23 \nAbbreviated Dtle: Foveal collicular bursts when releasing saccades 24 \n 25 \n  26 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 2 \nAbstract 27 \n 28 \nThe superior colliculus (SC) both senses the environment and orients gaze within it. While 29 \nthe SC’s sensory and motor bursts appear qualitaDvely similar to each other, populaDon 30 \nacDvity structure in the two processing regimes is very different, necessitaDng a hitherto 31 \nunexplored rapid representaDonal transformaDon, occurring on the scale of only tens of 32 \nmilliseconds. Here, using male rhesus macaque monkeys, we first show that when a planned 33 \nsaccade is released with a go signal, peripheral SC neurons represenDng the saccade target 34 \nlocaDon exhibit a transient, short-latency pause right before their motor bursts eventually 35 \nerupt. This pause starts within ~50 ms from the go signal, and it is sDmulus-dependent. It is 36 \nalso absent in the primary visual cortex, and is significantly weaker in purely visual SC 37 \nneurons than in saccade-related ones. Foveal SC neurons, on the other hand, burst, and 38 \ntheir bursts lead the peripheral neurons’ pauses by ~10 milliseconds. Remarkably, during 39 \nimmediate visually-guided saccade tasks, requiring a transformaDon from visual to motor 40 \nperipheral bursts in <50-100 ms, the transient foveal SC bursts sDll occur, resulDng in 41 \nsimultaneous short-latency bursDng at two disparate SC loci: one foveal; and one eccentric 42 \nand responding to the visual appearance of the saccade target. Our results suggest that in 43 \nclassic saccade tasks used to invesDgate visual, motor, and cogniDve processes in primate 44 \nbrains, a transient foveal SC signal may jumpstart peripheral saccadic orienDng by facilitaDng 45 \na necessary rapid representaDonal transformaDon needed for SC saccade motor bursts to 46 \nensue. 47 \n 48 \n 49 \n 50 \nSignificance 51 \n 52 \nStudies of eye movement control ohen involve behavioral paradigms involving sensing, 53 \ndeliberaDng, and ulDmately releasing an instructed rapid eye movement (saccade). While 54 \nthe sensing, deliberaDon, and movement aspects of saccades have been well studied in the 55 \npast, the releasing phase is less understood. Using classic saccade behavioral paradigms, we 56 \ndiscovered that foveal superior colliculus neurons exhibit transient acDvity bursts during 57 \ninstructed saccade releasing, which likely enables rapid representaDonal transformaDons 58 \nfrom a visual to a motor regime in the collicular neurons driving the eye movements. 59 \n  60 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 3 \nIntroduc3on 61 \n 62 \nAcDve vision entails a conDnual cycling between sensing, deliberaDon, and acDon (Findlay, 63 \n1982; Wolpert et al., 1995; Findlay and Walker, 1999; Buonocore and Hafed, 2023). In the 64 \noculomotor system, the neuronal mechanisms underlying the different subcomponents of 65 \nacDve vision have classically been studied using behavioral paradigms that aiempt to 66 \ndissociate these subcomponents from one another as much as possible. For example, in the 67 \ndelayed visually-guided saccade paradigm (Hikosaka and Wurtz, 1983; Munoz and Wurtz, 68 \n1995b), a visual sDmulus first appears, but the iniDally fixated spot remains visible. This 69 \nprevents a reflexive saccade to the appearing sDmulus and allows invesDgaDng visual 70 \nsensory processing mechanisms independent of an overt motor output. Then, aher some 71 \ndelay, during which cogniDve processes related to deliberaDon and motor planning may be 72 \ninvesDgated, the iniDally fixated spot disappears, allowing a saccade towards the eccentric 73 \nsDmulus to be subsequently triggered. In this case, motor-related processes associated with 74 \nsaccade generaDon can be studied under a constant, steady-state visual appearance of the 75 \nenvironment. 76 \n 77 \nAmong the many insights gleaned from the classic delayed saccade paradigm, it was recently 78 \nrecognized that this paradigm addiDonally highlights a fundamental problem in sensory-79 \ndriven motor behavior, namely the need to transform neuronal representaDons from a 80 \nsensory regime to a motor regime, ohen in the very same neurons and within very short 81 \nDme intervals (Jagadisan and Gandhi, 2022; Baumann et al., 2023; Bourrelly et al., 2023; 82 \nHeusser et al., 2023). For example, populaDon acDvity subspaces in the superior colliculus 83 \n(SC) are different from each other at sDmulus onset and saccade generaDon (Jagadisan and 84 \nGandhi, 2022; Baumann et al., 2023). And, at the individual neuron level, some SC neurons 85 \ncan prefer a parDcular visual image feature in the sDmulus onset phase of trials, but a 86 \ndifferent image feature in the saccade generaDon phase (Baumann et al., 2023). This rapid 87 \nalteraDon in operaDng regimes of idenDcal neurons likely necessitates a switch-like 88 \nmechanism at some point during delayed saccade task trials, and this is what we 89 \ninvesDgated here. 90 \n 91 \nWe specifically hypothesized that the go, or release, signal for saccades may be associated 92 \nwith neuronal dynamics that were not previously characterized in sufficient detail. Indeed, 93 \npast studies generally focused on neuronal acDvity for (peripheral) neurons represenDng the 94 \neccentric locaDons of the saccade targets. These studies uncovered well known sensory, 95 \ncogniDve, and motor processes associated with the neurons driving the eye movements. 96 \nHowever, it was not known what specifically happens to foveal representaDons in the SC at 97 \nthe Dme of the go signal; since acDve vision ulDmately starts and ends with the fovea, 98 \nunderstanding foveal SC representaDons when releasing saccades is important. 99 \n 100 \nTo address this gap, we studied the acDvity of peripheral SC and primary visual cortex (V1) 101 \nneurons during the delayed saccade paradigm, with a parDcular focus on neuronal acDvity 102 \naround the Dme of the go signal. We found that releasing an instructed eye movement in 103 \nthis paradigm is associated with a short-latency transient pause in SC, but not V1, acDvity 104 \nright before SC saccade-related motor bursts ensue. Importantly, this pause is preceded by 105 \nfoveal SC bursts ~10 ms earlier, and the foveal burst properDes suggest that they could be a 106 \ngeneralized trigger signal rather than a sDmulus-dependent phenomenon. Remarkably, 107 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 4 \nwhen we switched our paradigm to instead employ immediate visually-guided saccades, SC 108 \nfoveal bursts sDll happened, and thus temporally coincided with peripheral visual responses 109 \nto target onsets in other SC neurons. 110 \n 111 \nOur results reveal novel neuronal dynamics in the foveal SC at the Dme of the go signal in 112 \nclassic eye movement paradigms that have been used for several decades to study 113 \npercepDon, cogniDon, and acDon. These results also moDvate invesDgaDng mechanisms of 114 \nfoveal-to-peripheral, and vice-versa, neuronal modulaDons in the SC and other brain 115 \nstructures, especially when these modulaDons may not always be trivially explained by 116 \nclassic lateral inhibitory mechanisms (Munoz and Istvan, 1998; Trappenberg et al., 2001; Isa 117 \nand Hall, 2009; Marino et al., 2011; Satel et al., 2011; Phongphanphanee et al., 2014). 118 \n 119 \n 120 \n 121 \nMethods 122 \n 123 \nResearch animals and ethical approvals 124 \nThis study involved a re-analysis of data collected previously for other publicaDons 125 \ninvesDgaDng other research quesDons. In all cases, we analyzed data collected from male 126 \nrhesus macaque monkeys. For analyzing peripheral SC and V1 acDvity in the delayed visually-127 \nguided saccade task (see below for the details of the different behavioral tasks), we used the 128 \nsame database as the one in (Baumann et al., 2023). For analyzing foveal SC acDvity in the 129 \ndelayed visually-guided saccade task, we used the control condiDons of (Zhang et al., 2025). 130 \nAnd, for analyzing peripheral and foveal SC acDvity in the immediate visually-guided saccade 131 \ntask, we employed the control condiDons of (Zhang et al., 2026). 132 \n 133 \nIn all cases, all experiments were approved by ethics commiiees at the regional 134 \ngovernmental offices of Tübingen. 135 \n 136 \n 137 \nBehavioral tasks 138 \n 139 \nSaccades-to-gra-ngs task for peripheral SC and V1 neurons. For peripheral SC and V1 acDvity 140 \nin the delayed saccade condiDon, the behavioral task was the “saccades-to-graDngs” 141 \nparadigm (Baumann et al., 2023). This task was a slight modificaDon of the classic delayed 142 \nvisually-guided saccade paradigm. Briefly, the monkeys first saw a white fixaDon spot. Aher 143 \nthey fixated it by a few hundred milliseconds, a visual target appeared eccentrically, 144 \ncentered on the recorded neurons’ response field (RF) locaDons. The target consisted of a 145 \ndisc of 3 deg radius, the inside of which had a sine wave graDng. We always placed a white 146 \nspot (like the fixaDon spot) at the center of the disc, surrounded by a small gray disc (to 147 \navoid visibility loss of the spot due to the background sine wave graDng). This placement 148 \nallowed the saccades to be accurately made towards the disc’s center, which was criDcal for 149 \nthe previous study (but it did not influence the scienDfic quesDons of the present one). In 150 \nthe spaDal frequency version of the task, the sine wave graDng was verDcal and had 100% 151 \ncontrast, but it could have different spaDal frequencies across different trials. In the contrast 152 \nversion of the task, we fixed the spaDal frequency to 1 cycle/deg (1 cpd) and instead varied 153 \nthe contrast of the verDcal graDng from trial to trial. And, finally, in the orientaDon version of 154 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 5 \nthe task, both the spaDal frequency (1 cpd) and contrast (100%) were fixed, and the 155 \norientaDon of the graDng was varied from trial to trial. Aher maintaining fixaDon for another 156 \nfew hundred milliseconds aher target onset, the fixaDon spot was removed, and this was the 157 \ncue for the monkeys to generate a visually-guided saccade towards the eccentric target. 158 \nThus, the fixaDon spot removal was the go signal in this task, as is the case in classic 159 \ninstanDaDons of it. Trials from each version of the task were collected in separate blocks. 160 \n 161 \nSaccades-to-gra-ngs task for foveal SC neurons. For foveal SC acDvity in the delayed saccade 162 \ncondiDon, the behavioral task was similar to the one above (Zhang et al., 2025). Specifically, 163 \naher fixaDng the fixaDon spot, an eccentric target appeared. Again, it consisted of a disc of 3 164 \ndeg radius, the inside of which had a verDcal sine wave graDng of 100% contrast and either 1 165 \ncpd (low) or 4 cpd (high) spaDal frequency. There was no spot placed at the center of the 166 \ngraDng in this case. The target appeared at 8 deg eccentricity either to the right or leh of 167 \nfixaDon (except in two sessions in which it was placed at an oblique posiDon of similar 168 \neccentricity; ~10 deg). Aher maintaining fixaDon for a few hundred milliseconds aher target 169 \nonset, the fixaDon spot was removed, instrucDng the generaDon of the saccade towards the 170 \neccentric graDng. Aher fixaDng the graDng for another 500 ms, this graDng was removed, 171 \nand the monkeys were rewarded. A short inter-trial interval (with a blank gray screen) then 172 \nensued. 173 \n 174 \nImmediate visually-guided saccade task for perihpheral and foveal SC neurons. For 175 \nperipheral and foveal SC acDvity in the immediate saccade condiDon, we employed a classic 176 \nreflexive visually-guided saccade paradigm; the control condiDon of (Zhang et al., 2026). 177 \nSpecifically, the monkeys fixated a white fixaDon spot. Aher a few hundred milliseconds, the 178 \nfixaDon spot was removed and a simultaneous saccade target (white disc of 0.51 deg radius) 179 \nappeared either at the peripheral neurons’ RF posiDons or at an eccentricity >3.5 deg from 180 \nthe fovea for the foveal neurons. 181 \n 182 \nRF mapping tasks. The delayed saccade tasks above allowed us to invesDgate neuronal 183 \ndynamics at the Dme of transiDoning from a visual regime (aher sDmulus onset and waiDng 184 \nfor saccade instrucDon) to a motor regime (aher the go signal). The reflexive saccade task, 185 \non the other hand, allowed us to explore what happens when the transiDon from visual to 186 \nmotor regimes needed to happen much more urgently, as quickly as possible aher 187 \nperipheral target onset. In all cases, we also mapped neuronal RF’s in the same sessions, and 188 \nthis was done in order to idenDfy the RF’s posiDons relaDve to the eccentric saccade target. 189 \nOur RF mapping tasks (Chen et al., 2015; Chen and Hafed, 2017; Chen et al., 2018; Chen et 190 \nal., 2019) involved fixaDng a fixaDon spot, like in all tasks above. Aher a few hundred 191 \nmilliseconds of fixaDon, a white spot appeared at some locaDon on the display, and it 192 \ntypically remained on for 300-500 ms, before being turned off again. Across trials, we 193 \nchanged the posiDon of the appearing spot, in order to construct the RF maps of the 194 \nneurons. 195 \n 196 \n 197 \nData analysis and sta6s6cal tests 198 \n 199 \nAll saccadic eye movements were previously detected for the purposes of the earlier studies 200 \n(Baumann et al., 2023; Zhang et al., 2025; Zhang et al., 2026). Similarly, all neuronal 201 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 6 \npreprocessing (such as spike sorDng) was performed earlier. Our subsequent analyses were 202 \ngeared for the specific scienDfic purposes of the present study. 203 \n 204 \nTo characterize visual RF’s of neurons (e.g. Figs. 1A, C, 5A, C in Results), we averaged firing 205 \nrate in an interval 50-150 ms aher sDmulus onset, and we ploied it as a funcDon of the 206 \nhorizontal and verDcal posiDon of the appearing sDmulus (including interpolaDon in 207 \nbetween sampled posiDons). For some analyses, we also characterized the sDmulus-offset 208 \nresponses of the recorded neurons from the RF mapping data (parDcularly for the foveal 209 \nneurons in the delayed saccade paradigm). In this case, we simply measured average firing 210 \nrate 50-150 ms aher the offset of the target in the same RF mapping task. As we explain in 211 \nResults, this analysis was aimed at checking whether the removal of the fixaDon spot in our 212 \nmain saccade paradigms caused offset responses in the foveal neurons. Thus, for measuring 213 \noffset responses from the RF mapping task, we picked sDmulus locaDons in the RF mapping 214 \ndata that were consistent with the eccentricity of the fixaDon spot (in the main tasks) from 215 \nthe foveal neuron’s RF hotspot locaDon. In other words, because foveal SC neurons are 216 \nstrongly lateralized (Chen et al., 2019), fixaDon spot removal in the main tasks involved an 217 \noffset of a sDmulus that was at some non-zero distance, r, from the hotspot of the recorded 218 \nfoveal neurons. Therefore, from the RF mapping data, we defined a ring around the hotspot 219 \nlocaDon of each foveal SC neuron with radius of r deg (+/- 0.25 deg), where r was the 220 \neccentricity of the RF hotspot from the fixaDon spot. Then, we picked all sampled RF 221 \nmapping trials in this ring of locaDons that were also in the contralateral hemifield relaDve to 222 \nthe recorded SC side (we picked contralateral locaDons to maximize the likelihood of 223 \nobserving an offset response if it did exist), and we measured offset responses from these 224 \ntrials in parDcular. We then compared these offset responses to those associated with the go 225 \nsignal in the main saccade tasks (which are described in Results). 226 \n 227 \nFor the main saccade tasks, we ploied firing rates as a funcDon of Dme from target onset, 228 \nsaccade onset, and go signal onset (fixaDon spot removal). The first two kinds of plots are 229 \nsimilar to what was done previously, by us (Baumann et al., 2023; Zhang et al., 2025; Zhang 230 \net al., 2026) and others; we included them here for providing the context associated with 231 \nthe third kind of plot, which was of interest for us in the current study. As we show in 232 \nResults, this third plot gave either transient pauses or transient bursts in acDvity (shortly 233 \naher the go signal), depending on the neuron locaDon and behavioral task. To characterize 234 \nthese transient responses, we measured average firing rate in the interval 50-150 ms aher 235 \ngo signal onset. For a reference, we also measured firing rate in the final 100 ms before go 236 \nsignal onset. This gave a baseline to which we compared go-signal responses when assessing 237 \nwhether there was a burst or pause occurring aher the go signal. Such a comparison was 238 \nmade either by plotng the two measures directly against each other for each neuron, or by 239 \nobtaining a neuronal modulaDon index. When assessing transient pauses (see Results), we 240 \ndefined the modulaDon index as the firing rate aher the go signal (50-100 ms) minus the 241 \nfiring rate before the go signal (final 100 ms), divided by the sum of the two firing rates. 242 \nNegaDve modulaDon indices meant reducDons in firing rate aher the go signal. 243 \n 244 \nWe also someDmes classified trial condiDons (e.g. different spaDal frequencies in the spaDal 245 \nfrequency task) as a funcDon of sustained acDvity level they gave in a given neuron at the 246 \nend of the delay period (right before go signal onset). Specifically, we looked for the 247 \ncondiDon that gave the highest sustained acDvity and called it the most preferred sustained 248 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 7 \nfeature. Similarly, we looked for the image condiDon that gave the lowest sustained acDvity, 249 \nand we called it the least preferred sustained feature. This allowed us to check whether 250 \ntransient pauses aher the go signal that we characterize in Results depended on the starDng 251 \nfiring rate that was present at the Dme of the go signal. 252 \n 253 \nSimilarly, we divided SC neurons according to their funcDonal type (such as visual or visual-254 \nmotor neurons). We used classificaDons that we used previously (Baumann et al., 2023). 255 \nThus, we did not reclassify the neurons here. 256 \n 257 \nTo compare transient pauses and bursts directly (e.g. Fig. 7 in Results), we normalized 258 \nindividual neuron firing rates and then combined neurons by averaging their normalized 259 \nfiring rate curves. The normalizaDon was achieved by measuring, for each neuron, the 260 \naverage firing rate in the final 100 ms before go signal onset, and then dividing the enDre 261 \nfiring rate curve by this value. Thus, the normalized firing rate was 1 at the go signal, and 262 \nbursts/pauses were higher/lower than 1. SomeDmes, we also kept firing rates unnormalized, 263 \nbut we baseline-subtracted them based on the final 100 ms before the go signal. Thus, in 264 \nthis case, pauses were associated with negaDve baseline-subtracted firing rates. 265 \n 266 \nSimilarly, to assess the relaDve Dming between transient pauses and transient bursts in the 267 \ndelayed saccade paradigm (e.g. Fig. 7 in Results), we relied on individual spike Dmes. Across 268 \nall trials and all neurons (either foveal or peripheral), we binned spike Dmes around the go 269 \nsignal into 2-ms non-overlapping Dme bins. Then, we ploied a histogram of all spike Dmes. 270 \nFor the peripheral neurons, they paused aher the go signal (see Results). Thus, starDng from 271 \n10 ms aher the go signal, we searched for the first Dme point at which the histogram of 272 \nspike Dmes had 3 consecuDve drops in spike likelihood aher the go signal. This was 273 \nconsidered the populaDon latency of the pause. For the foveal neurons, which burst instead 274 \n(see Results), we searched for the first Dme point at which the histogram of spike Dmes had 275 \n3 consecuDve increases in spike likelihood aher the go signal. This was considered the 276 \npopulaDon latency of the burst. 277 \n 278 \nFor foveal neurons, we also someDmes looked at task context. Specifically, we compared 279 \nfoveal bursts that we got from the go signal (see Results) to potenDal bursts that might be 280 \nassociated with the offset of a foveal target sDmulaDng the recorded neurons’ RF’s. We 281 \nobtained the laier from the ends of the trials in the delayed saccade paradigm used to study 282 \nthe foveal neurons. As menDoned above, aher the monkeys fixated the graDng with a 283 \nsaccade, the graDng covered the fovea, and thus sDmulated the recorded foveal neurons’ 284 \nRF’s (Zhang et al., 2025). When the graDng disappeared, signaling the end of the trial, the 285 \nmonkeys were without any task-instrucDon and could look wherever they wanted. We 286 \nmeasured firing rates aher such graDng disappearance, to look for potenDal sDmulus-offset 287 \nresponses in the neurons. To ensure that there were no influences of potenDal saccades, we 288 \nonly included cases in which there were no saccades aher graDng disappearance for at least 289 \n150 ms. This way, we had an offset of a visual sDmulus in the recorded RF’s, but there was no 290 \ninstructed saccade context (as was the case with the fixaDon spot offset of the go signal in 291 \nthe main task). 292 \n 293 \nFor the immediate saccade task, we used similar analyses to the ones above. For populaDon 294 \nfiring rates, we normalized the firing rate of each neuron by the peak visual or foveal burst 295 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 8 \nresponse (see Results). Specifically, we first subtracted the average acDvity of each neuron in 296 \nthe final 100 ms before sDmulus onset from all firing rates at all Dmes in the trials (Zhang et 297 \nal., 2026). Then, we divided the firing rate curves by the peak value occurring 50-100 ms 298 \naher sDmulus onset (Zhang et al., 2026). Then, we averaged across all neurons. This allowed 299 \nus to focus on the Dming dynamics between foveal and peripheral bursts in this task, as well 300 \nas on the relaDonships of the bursts to saccadic reacDon Dmes. 301 \n 302 \nFor such saccadic reacDon Dme relaDonships, for each neuron, we split the trials into ones 303 \nwith saccadic reacDon Dmes faster than the median value of the session and ones with 304 \nlonger reacDon Dmes than the median value of the session. Then, we evaluated the 305 \nperipheral and foveal bursts for both groups of trials separately across neurons. 306 \n 307 \nStaDsDcally, we always showed standard error of the mean ranges in all plots. For 308 \ncomparisons between condiDons, we used signrank tests, rank sum tests, or t-tests. 309 \nSomeDmes, we split foveal SC neurons as ones with or without a foveal burst at the go 310 \nsignal. This classificaDon was made staDsDcally. If the neuron’s firing rate 50-150 ms aher the 311 \ngo signal was significantly higher than in the final 100 ms before the go signal with an t-test, 312 \nthen the neuron was classified as having a foveal burst; otherwise, it was not. This allowed 313 \nus to compare foveal bursts to sDmulus-offset responses from RF mapping tasks. 314 \n 315 \n 316 \n 317 \nResults 318 \n 319 \nWe first invesDgated the dynamics of switching between fixaDon and saccade generaDon in 320 \nthe standard delayed saccade paradigm. In this paradigm, monkeys fixate an iniDal fixaDon 321 \nspot, and an eccentric saccade target appears. The monkeys withhold saccadic orienDng 322 \ntowards the eccentric target unDl a go signal arrives, which comes in the form of fixaDon 323 \nspot disappearance. Classic SC recordings of peripheral neurons in this task demonstrate 324 \nvisual responses to target onset followed by motor bursts at saccade onset, ohen in the very 325 \nsame neurons (Mohler and Wurtz, 1976; Munoz and Wurtz, 1995b; Massot et al., 2019; 326 \nJagadisan and Gandhi, 2022; Baumann et al., 2023). Here, we were interested in the 327 \nneuronal dynamics that take place in between these two phases, and parDcularly at the Dme 328 \nof the go signal. Moreover, from the same task, we also recorded from foveal SC neurons, 329 \nwhich presumably should not burst for either target or saccade onset because of the 330 \ndisparity between their RF locaDons and the saccade target locaDon (Munoz and Wurtz, 331 \n1993a, b; Dorris and Munoz, 1995; Dorris et al., 1997; Everling et al., 1998; Munoz and 332 \nIstvan, 1998; Everling et al., 1999; Munoz et al., 2000; Hafed and Krauzlis, 2008; White et al., 333 \n2013). 334 \n 335 \nIn what follows, we first start by characterizing peripheral SC and V1 neuronal acDvity in the 336 \ndelayed saccade paradigm, demonstraDng a transient reset event in the SC, but not V1, 337 \nleading up to saccade-related motor bursts. We then document how foveal SC neurons 338 \nbehave at the Dme of the go signal in the same task, revealing a transient bursDng signal 339 \nthat precedes the peripheral SC reset event. Finally, we demonstrate that our observaDons 340 \nabout foveal bursts hold even in reflexive saccade tasks (without an enforced delay), 341 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 9 \nresulDng in the occurrence of two simultaneous short-latency neuronal acDvity bursts (aher 342 \nsaccade target onset) in two disparate SC loci, one foveal and one peripheral. 343 \n 344 \n 345 \nPeripheral superior colliculus neurons exhibit transient ac6vity pauses before 346 \ninstructed-saccade motor bursts emerge 347 \n 348 \nWe analyzed peripheral SC neuron acDvity from a “saccades-to-graDngs” task that we 349 \nrecently designed (Baumann et al., 2023) (Methods). Figure 1A, C shows the visual RF’s of 350 \ntwo example SC neurons from this task. The saccade target (schemaDzed by the white circle) 351 \nappeared over the neurons’ RF’s, which expectedly elicited visual responses by the neurons 352 \n(Fig. 1B, leh and Fig. D, leh); these visual responses were different for different image 353 \nappearances of the saccade target, consistent with the presence of feature tuning properDes 354 \nin SC neurons (Chen and Hafed, 2018; Chen et al., 2018; Bogadhi and Hafed, 2023; Hafed et 355 \nal., 2023). Since the two neurons were visual-motor neurons, at the Dme of saccade onset 356 \nlater on in the same trials (Fig. 1B, right and Fig. 1D, right), both neurons also emiied a 357 \nsaccade-related motor burst, which could again vary in strength depending on the visual 358 \nappearance of the saccade target (Zhang et al., 2022; Baumann et al., 2023; Hafed, 2025). 359 \nRemarkably, when we measured the acDvity of the two neurons around the Dme of the go 360 \nsignal (Fig. 1B, middle and Fig. 1D, middle), both neurons exhibited a short-latency transient 361 \npause in their acDvity (downward gray arrows). This pause occurred with a latency of ~50 ms 362 \nfrom the go signal occurrence, and it was apparently also all-or-none. That is, if the 363 \nsustained acDvity of the neuron was high for one image feature (e.g. 0.5 cpd for the neuron 364 \nof Fig. 1A, B or 11 cpd for the neuron of Fig. 1C, D), then the reducDon in firing rate aher the 365 \ngo signal was more marked than if the sustained acDvity was low (e.g. for 11 cpd in the 366 \nneuron of Fig. 1A, B and 2 cpd in the neuron of Fig. 1C, D); this resulted in more similar firing 367 \nrates aher the go signal than before it, regardless of the iniDal firing rate that was influenced 368 \nby the image appearance of the saccade target. Immediately aher each pause, the strong 369 \nmotor burst of each neuron erupted, as classically expected from saccade-related SC 370 \nneurons. 371 \n 372 \n  373 \n 374 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 10 \n 375 \n 376 \nFigure 1 Transient ac/vity pauses before the occurrence of saccade-related motor bursts in the SC. (A) Visual 377 \nresponse field of an example SC neuron. The white circle indicates the saccade-target loca<on and size; monkeys 378 \nwere only allowed to generate a saccade to the target upon a go signal (consis<ng of the removal of the fixa<on 379 \nspot; Methods) (Baumann et al., 2023). (B) The ac<vity of the same example neuron aligned to s<mulus onset in 380 \nthe main saccade task (leJ) , go signal onset (middle), and actual saccade onset (right). Two visual target 381 \nappearances of the saccade target are shown (each target had a small central spot to aid in saccade accuracy) 382 \n(Baumann et al., 2023) . Expected differences in visual (leJ) or motor (right) burst proper<es as a func<on of 383 \nimage appearance were observed (Chen and Hafed, 2018; Chen et al., 2018; Zhang et al., 2022; Baumann et al., 384 \n2023; Hafed et al., 2023; Hafed, 2025). Cri<cally, shortly aJer the go signal (middle), the neuron paused its 385 \nac<vity before the strong saccade-related burst could erupt. (C, D) Similar observa<ons from a second example 386 \nneuron, showing a <me -locked ac<vity pause aJer go signal before the motor bursts finally occurred (middle 387 \npanel in D). Numbers of trial repe<<ons per panel can be seen from the individual trial spike rasters shown. 388 \n 389 \n 390 \n 391 \nAcross the populaDon of SC neurons, and for all image features that we tested, we measured 392 \nneuronal acDvity in the final 100 ms before the go signal. Then, we subtracted the acDvity of 393 \neach neuron around the go signal from this baseline measurement, to obtain a baseline-394 \nsubtracted firing rate (Methods). When we aligned the baseline-subtracted firing rate of all 395 \nneurons to the go signal, we observed a short-latency reducDon in acDvity right before the 396 \nelevaDon associated with saccade-related motor bursts (Fig. 2A; SC data; trials with all image 397 \nfeatures were combined together). This was consistent with what we observed from the two 398 \nexample neurons of Fig. 1. We also measured the raw firing rate of each neuron, both in 399 \nbaseline (final 100 ms before the go signal) as well as 50-150 ms aher the go signal, and we 400 \ncompared the two measurements (Fig. 2B; trials with all image features were combined 401 \ntogether). Once again, across the populaDon, there was a robust reducDon in firing rate aher 402 \nthe go signal (p= 7.7693 x 10-23 for the spaDal frequency task; p=1.4893 x 10-19 for the 403 \ncontrast task; p=6.4765 x 10-18 for the orientaDon task; signrank test). 404 \n 405 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 11 \nThus, we observed a short-latency pause in SC acDvity when releasing an instructed saccade 406 \nin the classic delayed saccade paradigm. We think that this pause is funcDonally useful in the 407 \nSC, especially because it represents a perfect and Dmely-suitable opportunity to transform 408 \nSC representaDons from being in a visual regime to being in a motor regime (Jagadisan and 409 \nGandhi, 2022; Baumann et al., 2023; Heusser et al., 2023). 410 \n 411 \n 412 \n 413 \n 414 \n 415 \n 416 \n 417 \nFigure 2 Ubiquity of SC ac/vity pauses across task contexts, and a lack of a correlate for them in the primary 418 \nvisual cortex (V1) in similar behavioral tasks. (A) Popula<on firing rates aligned on the go signal from the same 419 \ntask as in Fig. 1. Here, we baseline-subtracted the ac<vity of each neuron based on firing rate in the final 100 ms 420 \nbefore go signal onset (Methods; numbers of neurons can be inferred from B, C). Across all three task variants 421 \n(Methods), SC ac<vity pauses were present to the same extent (downward arrow), but there were no such 422 \npauses in V1. The later increase in the SC curves is the saccade-related burst, and the even later V1 increase is 423 \nvisual reafference due to eye movement. (B) For each SC neuron, we measured ac<vity in the final 100 ms before 424 \ngo signal onset and ploWed it on the x-axis; on the y-axis; we measured average ac<vity 50-150 ms aJer the go 425 \nsignal. For each task, there was a reduc<on aJer the go signal. (C) There was no such reduc<on in V1. Numbers 426 \nof neurons are indicated in the figure, and sta<s<cal results are men<oned in the text. 427 \n 428 \n 429 \n 430 \n 431 \nWe also explored the SC pause properDes further, by linking them to the sustained acDvity 432 \nassociated with the image impinging on the visual RF’s of our recorded neurons. Different 433 \nimage features caused different levels of sustained SC acDvity (Chen and Hafed, 2018; Chen 434 \net al., 2018) (Figs. 1B, D, 3A). If the SC pause is all-or-none, then image features with higher 435 \nsustained acDvity should be associated with a bigger firing rate drop than image features 436 \nwith lower sustained acDvity; this would allow converging all SC firing rates to the same 437 \n(low) level regardless of the image condiDon driving the peripheral neurons’ acDvity. We 438 \nconfirmed this by finding, for each neuron, the image condiDon that gave rise to the highest 439 \nfiring rate in the final 100 ms before the go signal, and we called this the most preferred 440 \nsustained feature. We also found the image condiDon associated with the lowest sustained 441 \nfiring rate, and called it the least preferred sustained feature. Across neurons, the magnitude 442 \nof the drop in firing rate between the baseline (final 100 ms before the go signal) and post-443 \ngo (50-150 ms aher the go signal) intervals was larger for the most preferred than least 444 \npreferred sustained feature (Fig. 3B for the spaDal frequency task); there was a significant 445 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 12 \ndifference between the two image features (p= 3.9233 x 10-29; t-test). Results from the 446 \ncontrast and orientaDon tasks were virtually idenDcal, as also seen from Fig. 2A, B. 447 \n 448 \nThus, we idenDfied a systemaDc short-latency pause in SC acDvity at the Dme of releasing a 449 \ntask-instructed saccade in the classic delayed saccade paradigm. 450 \n 451 \n 452 \n 453 \n 454 \n 455 \nFigure 3 Dependence of peripheral SC ac/vity pauses on the viewed s/mulus appearance. (A) Ac<vity of a third 456 \nexample SC neuron at the <me of the go signal for three image appearances of the saccade target. During the 457 \ndelay period leading up to the go signal, the neuron had ongoing ac<vity that was different for the different 458 \nimages, reflec<ng a feature tuning property of the neuron (Hafed et al., 2023). As a result, the amount of ac<vity 459 \nreduc<on aJer the go signal was s<mulus-dependent: the pause was stronger  for the condi<on in which the 460 \ndelay-period ac<vity of the neuron was the highest, resul<ng in the same low ac<vity level regardless of ini<al 461 \nstate. (B) Across all neurons, we measured each neuron’s ac<vity in the final 100 ms before the go signal, and 462 \npicked the saccade-target image appearance that gave either the highest or lowest such ac<vity. Then, we 463 \nmeasured the pause strength (difference between ac<vity aJer the go signal and ac<vity before; Methods) for 464 \nthe most or least preferred image feature. The pause was stronger for the most preferred image feature, 465 \nconsistent with A. Note that only data from the spa<al frequency task is shown, but the other tasks revealed 466 \nsimilar results (also seen in Fig. 2). 467 \n 468 \n 469 \n 470 \nPeripheral superior colliculus ac6vity pauses are absent in the primary visual 471 \ncortex 472 \n 473 \nWe also wondered whether the transient pause that we saw in the SC was a general 474 \nproperty of visually-responsive neurons in other brain areas. Therefore, we collected a 475 \nsmaller number of V1 neurons from the same task (Methods). There was no transient pause 476 \naher the go signal, as can be seen from the V1 data in Fig. 2A. Given the fact that a large part 477 \nof visual responses in the SC derives from V1 (Wilson and Toyne, 1970; Lund, 1972; Schiller 478 \net al., 1974; May, 2006; Cerkevich et al., 2014; Zheng et al., 2024), this observaDon confirms 479 \nthat SC visual responses are funcDonally transformed and not merely inherited from the 480 \ncortex (Wurtz and Mohler, 1976; Hafed et al., 2023; Troienberg et al., 2026). 481 \n 482 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 13 \nAlso note that in the V1 neurons, there was a later elevaDon of neuronal acDvity well aher 483 \nthe go signal (Fig. 2A), almost 100 ms later than the elevaDon seen for the SC neurons. This 484 \nlater elevaDon reflects visual reafferent responses in V1 as a result of eyeball rotaDons, 485 \nwhereas the earlier SC increase in firing rate (aher the pause) represents the SC saccade-486 \nrelated motor bursts. Figure 2C also shows that in V1, there was no staDsDcally significant 487 \ndifference between acDvity right before and right aher the go signal (p=0.6165 for the 488 \nspaDal frequency task; p=0.4209 for the contrast task; p=0.5876 for the orientaDon task; 489 \nsignrank test), again confirming the absence of a transient pause in V1 neurons. 490 \n 491 \nTherefore, our results so far indicate that we observed a transient pause in SC acDvity at the 492 \nDme of the go signal in a classic delayed saccade paradigm. This pause was not a general 493 \nproperty of other brain areas that might be recruited by the same paradigm, and that might 494 \nmodulate SC acDvity, such as V1. 495 \n 496 \n 497 \nPeripheral superior colliculus ac6vity pauses are stronger in saccade-related 498 \nneurons 499 \n 500 \nAs menDoned above, the presence of an SC pause at the go signal might be funcDonally 501 \nparDcularly useful, because it is only in the SC, and not in V1, that the very same neurons 502 \nwould be engaged in both visual processing and saccade-related modulaDons (Jagadisan and 503 \nGandhi, 2022; Baumann et al., 2023; Hafed et al., 2023; Heusser et al., 2023; Hafed, 2025). If 504 \nthis is true, then one might expect that this pause should be more relevant for saccade-505 \nrelated SC neurons than for purely visual ones; this is because it is the saccade-related 506 \nneurons that would exhibit both sensory and motor responses requiring a representaDonal 507 \ntransformaDon on a rapid Dme scale. To check this, we classified our SC neurons as being 508 \neither purely visual or motor-related. The visual neurons included visual-burst and visual-509 \ndelay neurons, and the motor-related neurons included visual-motor and purely motor 510 \nneurons, as defined previously (Baumann et al., 2023; Bogadhi and Hafed, 2023; Hafed et al., 511 \n2023). 512 \n 513 \nWe found that there were stronger pauses for the motor-related SC neurons than for the 514 \nvisual ones. For example, in Fig. 4A, B, we reploied the data of Fig. 2B but aher first 515 \nclassifying the neurons into the two groups menDoned above. Across all tasks, there were 516 \nbigger differences between the acDvity before and aher the go signal in the motor-related 517 \nneurons (Fig. 4B) than in the visual neurons (Fig. 4A). To quanDfy this further, we calculated a 518 \nmodulaDon index for each neuron (acDvity aher the go signal minus before the go signal, 519 \ndivided by the sum; Methods). This index was negaDve for acDvity pauses and zero for no 520 \npauses. In all tasks, the median value of the modulaDon index was more negaDve in the 521 \nmotor-related neurons than in the visual ones (Fig. 4C, D, E), and the differences between 522 \ndistribuDons of modulaDon indices across the two classes of neurons were staDsDcally 523 \nsignificant, but only marginally so for the orientaDon task (the results of the staDsDcal tests 524 \nare included in the legend of Fig. 4). Thus, the transient pause that we observed was 525 \nstronger for motor-related neurons. 526 \n 527 \nOf course, the presence of sustained acDvity at the Dme of the go signal is a prerequisite for 528 \nsuccessfully seeing a pause, if one is present at all. Thus, it might be suggested that the 529 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 14 \ndifferences in pause strengths that we saw in Fig. 4 between purely visual and motor-related 530 \nneurons could reflect a lack of sustained acDvity in the visual neurons. However, this was not 531 \nthe case. For example, inspecDon of the raw firing rates on the x-axis of Fig. 4A reveals that 532 \nthe purely visual SC neurons had similar sustained acDvity levels, in general, to the visual-533 \nmotor and motor neurons (x-axis in Fig. 4B). This is expected because visual neurons 534 \n(especially visual-delay ones) are known to conDnuously represent the presence of a visual 535 \nsDmulus over their RF’s. Thus, the results in Fig. 4 are not explained by the purely visual 536 \nneurons having no (or less) sustained acDvity at the Dme of the go signal than the motor-537 \nrelated neurons. 538 \n 539 \n 540 \n 541 \n 542 \n 543 \n 544 \nFigure 4 Specificity of SC ac/vity pauses for neurons related to the motor genera/on of saccades. (A) Similar 545 \nanalysis to Fig. 2B, but only purely visual SC neurons. Visual neurons were visual-burst and visual-delay neurons 546 \n(Hafed et al., 2023). There was minimal ac<vity reduc<on at the go signal in these neurons despite the presence 547 \nof delay-period ac<vity (p=9.8480 x 10 -4 for the spa<al frequency task, p= 3.9107 x 10-5 for the contrast task, 548 \np=3.0530 x 10-7 for the orienta<on task; signrank test); also see C-E. (B) Neurons that needed to emit a saccade-549 \nrelated motor burst aJer the go signal underwent clearer ac<vity reduc<ons (p=4.5489 x 10-21 for the spa<al 550 \nfrequency task, p=8.0457 x 10-16 for the contrast task, p=1.0135 x 10-12 for the orienta<on task; signrank test). (C, 551 \nD, E) Neuronal modula<on indices (Methods) for the results in A, B across the different task contexts. Visual-552 \nmotor and motor neurons had generally stronger reduc<ons in their ac<vity aJer the go signal than visual and 553 \nvisual-delay neurons (p=0.000532 for the spa<al frequency task, p=0.004 for the contrast task, p=0.0966 for the 554 \norienta<on task; Wilcoxon rank sum test comparing the distribu<on of visual-motor/motor modula<on indices 555 \nto the distribu<on of visual/visual-delay modula<on indices). The median values of the shown distribu<ons were: 556 \n-0.1069 and -0.0453 for visual-motor/motor neurons and visual/visual-delay neurons, respec<vely in C; -0.0981 557 \nand -0.036 in D; -0.0862 and -0.0537 in E. 558 \n 559 \n 560 \n 561 \n 562 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 15 \n 563 \nFoveal superior colliculus neurons exhibit transient bursts instead of pauses 564 \n 565 \nHaving established the presence of a short-latency acDvity pause in SC neurons right before 566 \nsaccade-related bursts erupt, we next asked what happens in foveal SC representaDons 567 \nduring the delayed saccade paradigm. Figure 5A, C shows the visual RF’s of two example 568 \nfoveal SC neurons. In both cases, the RF’s were contained within a reDnotopic eccentricity of 569 \n2 deg (dashed circle) (Chen et al., 2019), and the saccade target was at an eccentricity of 8-570 \n10 deg (Methods). At sDmulus onset (Fig. 5B, D, leh) and saccade onset (Fig. 5B, D, right), the 571 \ntwo neurons behaved as expected from foveal SC neurons when the saccade target is placed 572 \noutside of their RF’s: at sDmulus onset, there was either no modulaDon or a reducDon in 573 \nacDvity; and, at saccade onset, there was a strong pause when the peripheral neurons were 574 \nemitng their motor bursts. Both of these observaDons were documented before in the SC 575 \nliterature (Munoz and Wurtz, 1993b, a; Hafed and Krauzlis, 2008; Zhang et al., 2025). 576 \nRemarkably, right aher the go signal, both foveal SC neurons showed a very strong, short-577 \nlatency acDvity burst, which almost doubled or tripled the firing rate relaDve to its level at 578 \nthe Dme of the go signal (Fig. 5B, D, middle; upward gray arrows). This foveal burst occurred 579 \nright before the saccade-related pause that was seen in the foveal neurons’ acDvity at the 580 \nDme of saccade onset. Thus, unlike the peripheral SC neurons (Figs. 1-4), these two example 581 \nfoveal SC neurons showed acDvity bursts, rather than pauses, when releasing instructed 582 \nsaccades (Fig. 5). 583 \n 584 \n 585 \n 586 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 16 \n 587 \n 588 \nFigure 5 Transient ac/vity bursts, rather than pauses, in the foveal representa/on of the SC prior to saccade 589 \ntriggering. (A, B)  Similar to the formadng of Fig. 1 but now for an example foveal SC neuron. The RF was 590 \nconstrained in the central 2 deg of visual angle (A), and the saccade target was at a farther eccentricity (Zhang 591 \net al., 2025). In B, the neuron behaved as expected at the <mes of s<mulus (leJ) and saccade (right) onset. AJer 592 \nthe go signal (middle), the neuron showed a strong transient burst in ac<vity, and at a qualita<vely similar <me 593 \nto the peripheral pauses of Figs. 1-4. Note that this neuron is the same example neuron of Fig. 1 in (Zhang et al., 594 \n2025), but here we addi<onally showed the ac<vity at the <me of the go signal. (C, D) Similar observa<ons for a 595 \nsecond example foveal SC neuron. There was again a transient burst right aJer the go signal.  All other 596 \nconven<ons are like Fig. 1. Error bars denote SEM across trial repe<<ons. Panel A was adapted from (Zhang et 597 \nal., 2025). 598 \n 599 \n 600 \n 601 \n 602 \nJust like with the peripheral neurons, we also had mulDple visual features of the eccentric 603 \nsaccade target in the version of our delayed saccade paradigm that we used when recording 604 \nour foveal SC neurons (Methods). This allowed us to invesDgate whether there was any 605 \nsDmulus dependence of the foveal acDvity bursts. In Fig. 6A, the foveal burst of a third 606 \nexample foveal SC neuron is shown, but this Dme for the two visual appearances of the 607 \neccentric saccade target. In both cases, the strength of the foveal burst was the same. This 608 \nwas a general property across our populaDon of foveal SC neurons. Specifically, we 609 \nmeasured average firing rate 50-100 ms from go signal occurrence, and we did so for either 610 \nthe low or high spaDal frequency saccade target. There was no difference in foveal burst 611 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 17 \nstrength (p=0.8509; signrank test across the populaDon; n=33). Therefore, unlike in the 612 \nperipheral neurons, the foveal SC burst was not sDmulus-dependent. As we will show later 613 \nwith our Dming analyses, this burst might thus be a general trigger signal to jumpstart 614 \nperipheral saccadic orienDng, regardless of the peripheral target’s image appearance. 615 \n 616 \n 617 \n 618 \n 619 \n 620 \n 621 \n 622 \nFigure 6 Lack of s/mulus or direc/on dependence of the foveal bursts. (A) The foveal burst of an example SC 623 \nneuron for two visual appearances of the peripheral saccade target. The foveal burst was similar in strength for 624 \nthe two s<muli. Error bars denote SEM across trials. (B) We also checked whether the foveal burst depended on 625 \ncongruence between the recorded foveal SC hemifield and the saccade direc<on. There were no or moderate 626 \ndependencies on saccade direc<on (signrank test;  n=33). 627 \n 628 \n 629 \n 630 \n 631 \n 632 \nWe also checked whether the foveal SC burst depended on saccade direcDon. Specifically, 633 \nfoveal SC neurons are lateralized (Chen et al., 2019), just like peripheral ones are. Thus, if a 634 \nfoveal neuron was recorded from the right SC, then it represented the leh foveal space. In 635 \nthis case, a lehward eccentric saccade target would elicit motor bursts in the peripheral 636 \nneurons of the same SC as the recorded foveal neuron, whereas a rightward saccade would 637 \nelicit motor bursts in the opposite SC. As can be seen from Fig. 6B, there was no clear 638 \ndependence of foveal burst strength on saccade direcDon; for the high spaDal frequency 639 \nsaccade target, there was a staDsDcally significant result, but the magnitude of the 640 \ndifference between hemifield direcDons was not qualitaDvely different from that seen with 641 \nthe low spaDal frequency target (for which there was no staDsDcally significant difference 642 \nbetween saccade direcDons). Thus, foveal SC bursts (Figs. 5, 6A) also did not show a 643 \nsystemaDc dependence on saccade direcDon relaDve to the recorded neurons’ RF hemifields 644 \n(Fig. 6B). 645 \n 646 \n 647 \n 648 \n 649 \n 650 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 18 \nFoveal superior colliculus ac6vity bursts lead peripheral pauses 651 \n 652 \nOur results so far indicate that releasing an instructed saccade in the classic delayed saccade 653 \nparadigm is associated with a short-latency (foveal) burst in one part of the SC topographic 654 \nmap and a (more peripheral) pause in another (Fig. 7A). To understand the potenDal links 655 \nbetween these two types of neuronal responses further, we summarized SC populaDon 656 \nacDvity in the two groups of neurons, aher normalizing the acDvity of each neuron to its 657 \nacDvity in the final 100 ms before go signal onset. At the Dme of saccade onset (Fig. 7B), the 658 \nperipheral neurons emiied strong saccade-related motor bursts, and the foveal neurons 659 \ndecreased their acDvity, consistent with the example neurons of Fig. 5 and with the prior 660 \nliterature (Munoz and Wurtz, 1993b; Hafed and Krauzlis, 2008; Zhang et al., 2025). However, 661 \nthis relaDonship was completely reversed in the go signal epoch (Fig. 7C), with foveal 662 \nneurons now exhibiDng an approximately three-fold increase in their acDvity immediately 663 \naher the go signal and right before saccade triggering; this is consistent with the foveal burst 664 \nstrengths seen in the example neurons of Fig. 5. The peripheral neurons, on the other hand, 665 \npaused. InteresDngly, plotng the peripheral and foveal neurons together in Fig. 7C revealed 666 \nthat the foveal burst actually led the peripheral pause by some Dme. To beier quanDfy this 667 \nDming relaDonship, we binned spike Dmes in all neurons into 2 ms non-overlapping Dme 668 \nbins, and we esDmated spike likelihood in each Dme bin aher go signal onset. The onset of 669 \nthe foveal burst (defined as the first Dme point to have at least three successive increases in 670 \nspike likelihood; Methods) led the onset of the peripheral pause (defined as the first Dme 671 \npoint to have at least three successive decreases in spike likelihood; Methods) by 10 ms. 672 \n 673 \n 674 \n 675 \n 676 \n 677 \n 678 \nFigure 7 Temporal sequencing of foveal bursts and ac/vity pauses in the SC prior to saccade triggering.  (A) 679 \nSchema<c of the SC topographic map (Hafed and Chen, 2016; Chen et al., 2019; Hafed et al., 2021), with an 680 \nexample indica<on of the rela<ve posi<ons of neurons that were recruited in our popula<ons of recordings from 681 \neither the experiments of Figs. 1 -4 or those of Figs. 5 -6. (B) At the <me of saccade onset, peripheral neurons 682 \nexhibited a motor burst, and foveal neurons reduced their ac<vity, as expected (Mohler and Wurtz, 1976; Munoz 683 \nand Wurtz, 1993b, 1995b; Hafed and Krauzlis, 2008, 2012; Zhang et al., 2025). Error bars denote SEM across 684 \nneurons, and the normaliza<on factor for each neuron was the ac<vity level in the final 100 ms before go signal 685 \nonset; see C. (C) At the <me of the go signal, foveal neurons exhibited strong bursts, which started slightly earlier 686 \nthan the peripheral SC pauses. (D) We quan<fied this <ming differences by having 2 ms bins in which we 687 \nmeasured spike likelihood across all neurons. Then, we iden<fied the onset of the burst or the pause as the first 688 \n<me point at which the spike likelihood changed in the same direc<on (increase for bursts and decrease for 689 \npauses) for at least three more upcoming <me bins (Methods). The peripheral pauses lagged the foveal bursts 690 \nby 10 ms. 691 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 19 \nThus, foveal SC bursts at the Dme of releasing instructed saccades in the classic delayed 692 \nsaccade paradigm occur systemaDcally earlier than peripheral SC pauses, and may thus aid 693 \nin triggering the peripheral pauses. 694 \n 695 \n 696 \nFoveal superior ac6vity bursts reflect instructed saccade context 697 \n 698 \nA parsimonious explanaDon for our results so far could relate to intrinsic RF properDes of SC 699 \nneurons (Hafed et al., 2023), combined with potenDal long-range lateral inhibiDon 700 \nmechanisms (Munoz and Istvan, 1998; Trappenberg et al., 2001; Isa and Hall, 2009; Marino 701 \net al., 2011; Satel et al., 2011; Phongphanphanee et al., 2014). Specifically, it could be 702 \npossible that the removal of the fixaDon spot in the delayed saccade paradigm may act as an 703 \noffset sDmulus to foveal SC neurons. Since SC neurons are expected to someDmes have 704 \noffset responses (i.e. acDvity bursts in response to an offset of a visual sDmulus that was 705 \npreviously present in their RF’s) (Humphrey, 1968; Schiller and Koerner, 1971; Cynader and 706 \nBerman, 1972; Goldberg and Wurtz, 1972b; Hafed et al., 2023), it is conceivable that the 707 \nfixaDon spot removal in our saccade paradigm could trigger an offset response in foveal SC 708 \nneurons. Aher such a response, lateral inhibiDon in the SC might, in turn, cause peripheral 709 \nneuron acDvity pauses (as a result of the foveal bursts). To invesDgate this potenDal cascade 710 \nof events, we first compared our foveal bursts to real offset responses as measured by our 711 \nRF mapping tasks. We then explored other situaDons with offsets of visual sDmuli in our 712 \nparadigms, but without an explicit task instrucDon to release a saccade. And, finally, we 713 \nexplored cases in which we created a compeDDon between putaDve lateral inhibiDon and 714 \nthe occurrence of peripheral SC acDvity bursts (rather than pauses), to understand whether 715 \nthe peripheral pauses are due to lateral inhibiDon from the foveal bursts or not. We describe 716 \nthe results of these three successive invesDgaDons next. 717 \n 718 \nTo explore whether foveal bursts at the go signal reflect offset responses to the removal of 719 \nthe fixaDon spot, we measured offset responses in our foveal SC neurons from our RF 720 \nmapping tasks (Methods). During RF mapping, we presented a small white spot (similar to 721 \nthe fixaDon spot) at different locaDons near the fixaDon spot that the monkeys were looking 722 \nat. Aher a few hundred milliseconds, the white spot was removed, allowing us to measure 723 \noffset responses. Figure 8A, B shows the offset responses of the two example foveal neurons 724 \nof Fig. 5. Because foveal SC RF’s are strongly lateralized (Chen et al., 2019) (Fig. 5A, C), 725 \nfixaDon spot removal in our main task was equivalent to an offset response for a sDmulus 726 \nthat was visible at a non-zero distance, r, from the RF hotspot eccentricity (assuming, rightly, 727 \nthat the monkeys properly centered gaze on the fixaDon spot, on average); here, r would be 728 \nthe distance between the RF hotspot and the central preferred reDnal locus of fixaDon. 729 \nTherefore, from the RF mapping data, we picked a ring of sampled sDmulus locaDons at a 730 \ndistance r from the RF hotspot (+/- 0.25 deg; Methods). We took all of these sDmulus 731 \nlocaDons in the hemifield of the RF hotspot (to maximize the likelihood of seeing offset 732 \nresponses), and we ploied the RF offset responses in Fig. 8A, B. As can be seen, at the same 733 \neccentricity from the RF hotspot as the fixaDon spot in the main task, the two example 734 \nneurons did not emit substanDal offset responses at all. For comparison, the insets in Fig. 8A, 735 \nB replicate the foveal bursts of Fig. 5 from the same neurons, showing that the neuronal 736 \nresponses at the go signal in the main task were very different from their responses for the 737 \noffset of small white spots near their RF hotspots. Thus, for these two example neurons, 738 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 20 \nfoveal bursts were not trivially explained by offset responses to the removal of the fixaDon 739 \nspot. 740 \n 741 \n 742 \n 743 \n 744 \n 745 \n 746 \nFigure 8 Dissocia/on between foveal bursts aTer the go signal and s/mulus-offset responses in the foveal SC 747 \nneurons. (A) For the example neuron of Fig. 5A, B, we measured the response of the neuron to the offset of a 748 \nsmall spot during the RF mapping task (Methods); we took care to define a band of eccentrici<es and direc<ons 749 \nin which the s<mulus loca<on was in a similar por<on of the RF as the disappearing fixa<on spot in the main task 750 \n(Methods). The neuron did not exhibit a substan<al offset response; for comparison, the inset shows the foveal 751 \nburst of the same neuron from Fig. 5B. Thus, the foveal burst was not an offset response to the disappearance 752 \nof the fixa<on spot in our saccade task. Error bars denote SEM across trial repe<<ons. (B) Similar observa<ons 753 \nfor the second example neuron of Fig. 5C, D. (C) For each neuron that exhibited a foveal burst in the main saccade 754 \ntask (Methods), we ploWed the foveal burst strength against the offset response of the neuron from the RF 755 \nmapping task (Methods). There was a moderate rela<onship between offset responses and foveal bursts (r = 756 \n0.6026, p = 0.0005 for the low spa<al frequency; r = 0.5924, p = 0.0007 for the high spa<al frequency). Each color 757 \nshows the foveal burst for a one spa<al frequency of the saccade target. (D) For neurons with no foveal burst in 758 \nthe main saccade task (Methods), they could s<ll exhibit offset responses in the RF mapping task (r = 0.2662, p 759 \n= 0.1166 for the low spa<al frequency ; r = 0.2890, p = 0.0874  for the high spa<al frequency) . Thus, C and D 760 \ncombined suggest that foveal bursts were not always explained by offset responses due to the disappearance of 761 \nthe fixa<on spot in the delayed saccade paradigm. (E) In the main saccade task, aJer a successful saccade to the 762 \ngra<ng, the gra<ng eventually disappeared, and the monkey was free to make any saccades in the inter-trial 763 \ninterval. The foveal neurons did not burst for the disappearance of the gra<ng, but they s<ll burst for the 764 \ndisappearance of the fixa<on spot during the instructed-saccade phase of the trial (p = 6.6424 x 10-8 for the low 765 \nspa<al frequency, p = 1.5453 x 10-7 for the high spa<al frequency; signrank test). Thus, foveal bursts were task-766 \ndependent. 767 \n 768 \n 769 \n 770 \n 771 \nAcross the populaDon of foveal SC neurons, we then collected offset responses and 772 \ncompared them to foveal bursts. In Fig. 8C, we took the neurons that staDsDcally exhibited 773 \nfoveal bursts at the go signal (Methods), and we invesDgated how they behaved in terms of 774 \noffset responses during the RF mapping task. The neurons did generally exhibit offset 775 \nresponses, as might be expected (Hafed et al., 2023). Importantly, we also looked at foveal 776 \nSC neurons that did not staDsDcally emit foveal bursts in the main delayed saccade task 777 \n(Methods). If our foveal bursts of Figs. 5-7 were fully explained by RF offset responses, then 778 \nthese neurons should not have exhibited any offset responses at all in the RF mapping task. 779 \nIn reality, this was not the case at all (Fig. 8D). There were clear offset responses in the RF 780 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 21 \nmapping task for the neurons that did not exhibit strong foveal bursts at the go signal in the 781 \nmain delayed saccade task. Thus, foveal bursts at the go signal in the classic delayed saccade 782 \nparadigm could be disDnct from simple offset responses associated with fixaDon spot 783 \nremoval. 784 \n 785 \nPerhaps the strongest evidence that we had for a dissociaDon between offset responses and 786 \nthe foveal SC bursts at the go signal came from our main delayed saccade task itself. 787 \nSpecifically, in this task, aher the monkeys foveated the instructed saccade target (the spaDal 788 \nfrequency graDng), this target eventually disappeared aher a few hundred milliseconds of 789 \nfixaDon (Methods). Since the monkeys had successfully foveated the saccade target prior to 790 \nthat, the removal of this target in this case was equivalent to an offset sDmulus for the 791 \nneurons’ RF’s. CriDcally, the monkeys had no explicit task instrucDon associated with the 792 \ntarget removal; this disappearance of the visual sDmulus was the onset of the inter-trial 793 \ninterval in which the monkeys were free to look wherever they wanted (Methods), and we 794 \nanalyzed neuronal acDvity of the foveal neurons upon target removal only when there were 795 \nno saccades for at least 150 ms aher the removal. As can be seen from Fig. 8E, the neurons 796 \nthat did show foveal bursts at the go signal (y-axis) did not show substanDal acDvity 797 \nelevaDons upon target removal (x-axis). 798 \n 799 \nThus, all of the analyses of Fig. 8 suggest that foveal SC bursts are dependent on the task 800 \ncontext, and may not trivially reflect simple sDmulus-offset responses due to fixaDon spot 801 \nremoval in the classic delayed saccade paradigm. 802 \n 803 \n 804 \nFoveal bursts cooccur with peripheral visual responses in reflexive saccade tasks 805 \n 806 \nIf foveal bursts are indeed not explained by sDmulus offset responses, then are the 807 \nperipheral SC pauses at least sDll explained via long-range lateral inhibiDon mechanisms in 808 \nthe SC (Munoz and Istvan, 1998; Trappenberg et al., 2001; Isa and Hall, 2009; Marino et al., 809 \n2011; Satel et al., 2011; Phongphanphanee et al., 2014)? We believe that this may not 810 \nnecessarily be the case, and our evidence for this comes from another classic saccade-811 \nrelated task, now not enforcing a delay period between fixaDon spot removal and eccentric 812 \nsaccade target appearance (Fig. 9A). When recording from peripheral SC neurons in this task, 813 \nshort-latency visual responses appear, before the saccade-related motor bursts quickly 814 \nevolve (Bell et al., 2006; Boehnke and Munoz, 2008; Marino et al., 2012; Marino et al., 2015; 815 \nTroienberg et al., 2026). If lateral inhibiDon was the sole determinant of complementary 816 \ntransient pauses and bursts at disparate SC loci (Fig. 7), then the peripheral visual bursts in 817 \nthis version of the saccade task might be expected to eliminate the foveal bursts that we 818 \nobserved above, and maybe even replace them with pauses instead. Thus, we recorded not 819 \nonly peripheral SC neurons, but also foveal ones in the classic reflexive, visually-guided 820 \nsaccade task (Fig. 9B). 821 \n 822 \nFigure 9C shows the acDvity of an example peripheral SC neuron. Here, we ploied the 823 \nneuron’s acDvity aligned on eccentric saccade target onset (which coincided with fixaDon 824 \nspot removal in this task; Fig. 9A), and aher subtracDng pre-sDmulus acDvity like we did 825 \nrecently (Zhang et al., 2026). The neuron exhibited a short-latency visual response, followed 826 \n<50-100 ms later by a second volley of spiking. This second volley of spiking was the 827 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 22 \nsaccade-related motor burst, as can be seen when aligning the same data to saccade onset 828 \n(Fig. 9D). Our prior work with this task has taught us that the same rapid transformaDon 829 \nfrom a visual to a motor regime also does take place in it (Baumann et al., 2023), suggesDng 830 \nthat a foveal trigger signal might sDll be recruited in such a task. Remarkably, this was indeed 831 \nthe case. When we recorded from an example foveal SC neuron in this task, it exhibited a 832 \nstrong foveal burst (Fig. 9E), before it expectedly paused at saccade onset (Fig. 9F). The net 833 \nresult was that the two example neurons of Fig. 9C-F provided suggesDve evidence for the 834 \nexistence of two simultaneous short-latency acDvity bursts in the SC at two very disparate 835 \nloci: one peripheral represenDng the saccade target appearance, and one foveal associated 836 \nwith the go signal for generaDng a saccade. 837 \n 838 \n 839 \n 840 \n 841 \n 842 \n 843 \nFigure 9 Persistence of foveal bursts even in immediate, visually-guided saccade tasks. (A) In this task, the go 844 \nsignal (fixa<on spot disappearance) coincided with the onset of the peripheral saccade target. (B) Thus, we could 845 \nask whether at the <me of the peripheral visual burst in response to target appearance, we could s<ll observe a 846 \nfoveal burst. (C, D) Example peripheral SC neuron showing expected ac<vity discharge: there was an ini<al visual 847 \nburst (C), followed immediately by a saccade-related motor burst (D). (E, F) Example foveal SC neuron from the 848 \nsame task. Remarkably, the foveal neuron burst (E) at the same <me as the peripheral visual burst in C. It then 849 \nreduced its ac<vity at saccade onset (F), as expected from foveal SC neurons (Munoz and Wurtz, 1993b; Hafed 850 \nand Krauzlis, 2012; Zhang et al., 2025). Trial numbers in C-F can be inferred from the spike rasters, and error bars 851 \ndenote SEM across trials. (G) Popula<on results for all peripheral neurons collected during this task. Error bars 852 \ndenote SEM across neurons. Visual and motor bursts were evident. (H) For the foveal neurons, they exhibited a 853 \nfoveal burst even when the peripheral neurons were burs<ng for the visual onset inside their RF’s (the faint blue 854 \ncurve is a replica<on of the curve in G to illustrate the similarity of the <ming of the two bursts).  The neurons 855 \nthen reduced their ac<vity when the peripheral neurons were burs<ng at saccade onset (post-saccadic reafferent 856 \nresponses also emerged). Thus, in the immediate, visually-guided saccade task, there are two simultaneous 857 \nbursts at two different loci in the SC aJer target appearance. Error bars denote SEM across neurons. 858 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 23 \n 859 \nAcross the populaDon, our results were consistent with those seen from the two example 860 \nneurons. Specifically, peripheral SC neurons showed expected biphasic responses consisDng 861 \nof a first visual burst followed by a later saccade-related motor burst (Fig. 9G). And, 862 \nremarkably, foveal SC neurons showed a transient burst at the same Dme as the peripheral 863 \nvisual bursts (Fig. 9H), before reducing their acDvity at the Dme of saccade onset. 864 \n 865 \nThus, the complementary nature of transient pauses and bursts at two disparate SC loci that 866 \nwe saw in the delayed saccade paradigm above (e.g. Fig. 7C) was not an obligatory 867 \nobservaDon dictated by lateral inhibiDon mechanisms. Clearly, simultaneous short-latency 868 \nbursts are possible in the SC (Fig. 9). InteresDngly, we also previously saw that it is possible 869 \nto observe simultaneous acDvity increases in two different locaDons on the SC map 870 \n(Buonocore et al., 2021), but in that case, it was a simultaneity between a peripheral visual 871 \nburst and a foveal microsaccade-related motor burst. Here, it was two transient non-872 \nsaccadic bursts that we observed. Similarly, prior experiments with peripheral SC transient 873 \npauses concluded that they were not fully explained by lateral inhibiDon from foveal SC 874 \nresponses to foveal image changes (Li et al., 2006). 875 \n 876 \n 877 \nPeripheral visual responses, but not foveal bursts, correlate with saccadic 878 \nreac6on 6me 879 \n 880 \nThe immediate saccade paradigm of Fig. 9A also allowed us to further explore addiDonal 881 \nproperDes of foveal SC bursts. Specifically, we asked to what extent these bursts might relate 882 \nto saccade Dming variability. In peripheral neurons, we replicated the expected finding that 883 \nSC visual responses are significantly stronger (and earlier) for faster saccadic reacDon Dmes 884 \n(Bell et al., 2006; Boehnke and Munoz, 2008; Marino et al., 2012; Marino et al., 2015; Chen 885 \net al., 2018; Troienberg et al., 2026). This can be seen from the populaDon results shown in 886 \nFig. 10A, C: here, we split the trials for each neuron according to whether the saccadic 887 \nreacDon Dme was faster or slower than the median of the session, and we found that the 888 \nfaster trials had stronger peripheral SC visual bursts (Fig. 10A, C). No such relaDonship 889 \nemerged for the simultaneously occurring foveal SC bursts (Fig. 10B, D), again suggesDng 890 \nthat these bursts might be a switch-like trigger signal that is independent of saccade-target 891 \nappearance (Fig. 6A), saccade direcDon (Fig. 6B), or saccade Dming (Fig. 10B, D). 892 \n 893 \n 894 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 24 \n 895 \n 896 \nFigure 10 Dissocia/on between foveal bursts and saccadic reac/on /mes in immediate, visually -guided 897 \nsaccade tasks. (A) In peripheral SC neurons, we replicated expecta<ons from the previous literature (Bell et al., 898 \n2006; Boehnke and Munoz, 2008; Marino et al., 2012; Marino et al., 2015; Chen et al., 2018; TroWenberg et al., 899 \n2026): visual bursts in response to target onset were weaker and slightly later for later saccadic reac<on <mes. 900 \nIn this figure, we split trials by the median saccadic reac<on <me of each session. Then, we ploWed the popula<on 901 \nfiring rates. Trials with late saccades (light blue; later saccade bursts than in the saturated blue) had much 902 \nweakened and slightly delayed visual bursts. Error bars denote SEM across neurons. (B) In the foveal neurons, 903 \nwe did not observe a clear difference in foveal bursts between trials with fast and slow saccadic reac<on <mes 904 \n(the different <mes of post-burst ac<vity reduc<ons in the two curves reflect the different <mes of saccade 905 \nonsets in the two sets of trials per neuron). Error bars denote SEM. (C) Individual neuron results from the analysis 906 \nof A. Visual bursts were stronger on fast trials (p = 2.6741 x 10-35; signrank test). n=253 neurons. (D) For foveal 907 \nneurons, there was no difference (p=0.059; signrank test). n=41 neurons. 908 \n 909 \n 910 \n 911 \n 912 \n 913 \nFinally, and for completeness, we also revisited the foveal bursts from our delayed saccade 914 \nparadigm. When we analyzed these bursts as a funcDon of saccadic reacDon Dme, we again 915 \nfound that the bursts had the same strength for either the fast or slow saccadic reacDon 916 \nDme trials (Fig. 11). Peripheral SC pauses also did not appear to have a systemaDc 917 \nrelaDonship to saccade Dming in the same task. 918 \n 919 \n 920 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 25 \n 921 \n 922 \nFigure 11 Dissocia/on between foveal bursts and saccadic reac/on /mes also in delayed saccade contexts. (A) 923 \nFor the delayed saccade task of Figs. 5-8, we split trials based on the median saccadic reac<on <me of a given 924 \nsession (just like we did for Fig. 10), and we then ploWed popula<on firing rates for the two split groups. Foveal 925 \nbursts were similar in both cases. (B) Similar results for the other spa<al frequency of the peripheral saccade 926 \ntarget. Thus, the foveal bursts behaved similarly in both versions of our visually -guided saccade paradigm in 927 \nterms of subsequent saccade <ming. Error bars denote SEM across neurons. 928 \n 929 \n 930 \n 931 \n 932 \nDiscussion 933 \n 934 \nWe invesDgated neuronal response dynamics at the Dme of “releasing” instructed saccades 935 \nin two classic visually-guided saccade paradigms. Such paradigms are rouDnely used in the 936 \nstudy of primate sensaDon, cogniDon, and acDon. We specifically idenDfied a transient 937 \nfoveal SC signal that may jumpstart peripheral saccadic orienDng. In delayed saccade 938 \nparadigms, this foveal signal leads peripheral SC acDvity pauses by ~10 ms, is not explained 939 \nby sDmulus-offset responses, does not depend on sDmulus appearance or saccade direcDon, 940 \nand is independent of eventual saccade Dming. Remarkably, in immediate saccade 941 \nparadigms, this transient foveal signal sDll occurs, resulDng in two simultaneous acDvity 942 \nbursts at two disparate loci in the SC topographic map. 943 \n 944 \nPeripheral SC acDvity pauses have been reported before. For example, Li and colleagues 945 \nemployed a foveal sDmulus change as a cue in a target selecDon paradigm. Peripheral SC 946 \nneurons exhibited transient pauses in their acDvity at the Dme of the foveal sDmulus change 947 \n(Li et al., 2006). Similar observaDons were made in a variety of related tasks, most of which 948 \ninvolving the appearance or modificaDon of a sizeable foveal visual sDmulus, and in mulDple 949 \nbrain areas like the SC, frontal eye fields (FEF), and lateral intraparietal area (LIP) (Li and 950 \nBasso, 2005; Dorris et al., 2007; White et al., 2013; Grimaldi et al., 2018; Cho et al., 2021; 951 \nShinn et al., 2022; SDne et al., 2023). Here, we explicitly recorded foveal SC neurons without 952 \npresenDng a new foveal sDmulus and demonstrated that peripheral SC pauses might be 953 \nrelated to a transient foveal trigger signal. Importantly, this signal is likelu not a simple 954 \nsensory response, because it clearly depended on the task context, and also because it was 955 \ndissociated from sDmulus-offset responses observed during RF mapping (Fig. 8). Moreover, 956 \nthe foveal trigger signal need not directly mediate peripheral pauses via lateral inhibiDon 957 \n(Munoz and Istvan, 1998; Trappenberg et al., 2001; Isa and Hall, 2009; Marino et al., 2011; 958 \nSatel et al., 2011; Phongphanphanee et al., 2014). This is because we saw peripheral visual 959 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 26 \nbursts at the same Dme as the foveal bursts in the immediate saccade paradigm (Figs. 9, 10); 960 \nin this case, it would be difficult for lateral inhibiDon mechanisms alone to account for such 961 \nsimultaneity of bursts. 962 \n 963 \nWe believe that there are at least two good reasons for transient peripheral SC pauses to 964 \noccur in our invesDgated paradigms. The first is biophysical. SC saccade-related bursts are 965 \nexplosive, and can exceed 1000 spikes/s (Goossens and van Opstal, 2012). Thus, a transient 966 \npause right before motor bursts could aid in the biophysical processes leading up to burst 967 \ngeneraDon (Aizawa et al., 1999; Saito and Isa, 2003; Moren et al., 2013). 968 \n 969 \nThe second reason why peripheral SC pauses may be funcDonally useful is that a large 970 \nnumber of saccade-related SC neurons are also sensory neurons as well (Massot et al., 2019; 971 \nHafed et al., 2023). This requires a representaDonal transformaDon between visual and 972 \nmotor regimes (Jagadisan and Gandhi, 2022; Ayar et al., 2023; Baumann et al., 2023; 973 \nBourrelly et al., 2023; Heusser et al., 2023), and this transformaDon even needs to happen 974 \nwithin only a few tens of milliseconds in the immediate saccade paradigm (Baumann et al., 975 \n2023). For example, Jagadisan and Gandhi (Jagadisan and Gandhi, 2022) showed that while 976 \nvisual and motor bursts in the SC can appear qualitaDvely similar to each other and reach 977 \nsimilar firing rates, the temporal structure of SC populaDon acDvity is altered at the Dme of 978 \nsaccade generaDon. In our subsequent confirmaDon of this observaDon, we also noted that 979 \nacDvity subspaces could be orthogonal to each other in the two neuronal regimes, and that 980 \nindividual neuron preferences for specific images can change between visual and motor 981 \nepochs (Baumann et al., 2023). Thus, peripheral SC pauses right before the motor bursts 982 \nwould consDtute a perfect resetng mechanism for rapid representaDonal transformaDons 983 \nto be implemented. It would be interesDng in future studies to understand how these 984 \ntransformaDons themselves emerge. 985 \n 986 \nIn terms of the fovea, prior work has recorded from the deep rostral SC during saccades. 987 \nConsistent pauses in foveal SC acDvity were observed at the Dme of saccade generaDon 988 \n(Munoz and Wurtz, 1993b, a). InteresDngly, there were sDll some hints in some of these 989 \nstudies for subtle elevaDons in foveal SC acDvity when releasing saccades by certain task 990 \nevents (Dorris and Munoz, 1995; Dorris et al., 1997; Everling et al., 1998; Munoz and Istvan, 991 \n1998; Everling et al., 1999; Munoz et al., 2000; Hafed and Krauzlis, 2008; White et al., 2013). 992 \nHowever, there was nothing reported that was as strong as we saw, and the foveal 993 \nelevaDons were not the focus of these earlier studies (and thus not exhausDvely 994 \ncharacterized). 995 \n 996 \nFrom the perspecDve of the peripheral reset alluded to above, our observed foveal bursts 997 \nare parDcularly interesDng. This is because they may act as the trigger signal jumpstarDng 998 \nperipheral pausing, and thus acDvely parDcipate in the orienDng process. Consistent with 999 \nthis, our foveal bursts were not sDmulus or saccade-direcDon dependent. They were also not 1000 \nrelated to subsequent saccade Dming, unlike (peripheral) visual bursts (Bell et al., 2006; 1001 \nBoehnke and Munoz, 2008; Marino et al., 2012; Marino et al., 2015; Troienberg et al., 1002 \n2026). And, most importantly, they sDll occurred in the immediate saccade paradigm, which 1003 \nsDll requires a representaDonal transformaDon between visual and motor regimes 1004 \n(Baumann et al., 2023). Of course, the quesDon is: what drives these bursts? In our work, we 1005 \ntried to dissociate them from simple offset responses due to the removal of the fixaDon 1006 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 27 \nspot. InteresDngly, we found that target removal at the ends of trials in the main delayed 1007 \nsaccade paradigm was not associated with foveal bursts, suggesDng that the bursts were 1008 \nindeed dependent on the context of releasing a planned, instructed saccade. 1009 \n 1010 \nMore broadly, we think that it is not unheard of for a foveal signal in the SC to be relevant 1011 \nfor peripheral SC processes. For example, we recently found, in the context of peri-1012 \nmicrosaccadic changes in peripheral visual sensiDvity, that exclusive experimental control 1013 \nover foveal SC state is sufficient to modulate peripheral visual sensiDvity (Zhang et al., 2026). 1014 \nSimilarly, in the opposite direcDon, we also found that foveal SC state can be modulated by 1015 \nperipheral SC state across saccadic eye movements (Zhang et al., 2025). These observaDons 1016 \nmay relate to wider concepts like traveling waves. While such waves are presently gaining 1017 \nmore research interest, classic SC work has indeed demonstrated a potenDal role of such 1018 \nwaves in acDve vision (Munoz and Wurtz, 1995a; Nakahara et al., 2006). In the future, it 1019 \nwould be interesDng to invesDgate such waves in more detail. For example, we can aiempt 1020 \nto understand the links between foveal bursts and peripheral pauses by blocking the Inputs 1021 \nto the SC from the cortex and invesDgaDng whether signatures of an impact of foveal bursts 1022 \nsDll appears in the peripheral SC representaDon aher losing corDcal drive. 1023 \n 1024 \nWe are also especially intrigued by our observaDon of simultaneous bursts in the foveal and 1025 \nperipheral SC in the immediate visually-guided saccade paradigm. These simultaneous bursts 1026 \nare significant because they suggest that the peripheral pauses in the delayed saccade 1027 \nparadigm may not necessarily result from lateral inhibiDon mechanisms. In fact, in the 1028 \nimmediate saccade paradigm, it was known for many decades that peripheral visual bursts 1029 \nare actually enhanced, rather than suppressed, relaDve to visual bursts during fixaDon 1030 \n(Goldberg and Wurtz, 1972a). Since it is very likely that foveal bursts sDll occurred in these 1031 \nclassic experiments (Goldberg and Wurtz, 1972a), had they been invesDgated, it remains to 1032 \nbe seen whether the foveal bursts may actually aid in the peripheral enhancement. 1033 \nCertainly, in our recent work, we found that enhancing pre-sDmulus acDvity in the foveal SC 1034 \ncan indeed help in enhancing peripheral visual bursts (Zhang et al., 2026). We should also 1035 \nnote that there are other observaDons in the literature for which direct evidence of lateral 1036 \ninhibiDon between the foveal and peripheral SC representaDons was absent. For example, 1037 \nwhen we invesDgated microsaccade generaDon in the foveal SC representaDon, we found 1038 \nthat there could sDll be microsaccade-related foveal SC motor bursts at the exact same Dme 1039 \nas visually-driven peripheral SC bursts (Buonocore et al., 2021), and we again argued that 1040 \nlateral inhibiDon would not explain these observaDons. It would be interesDng in the future 1041 \nto understand the condiDons under which physiological correlates of a lack of lateral 1042 \ninhibiDon would be most likely to occur. 1043 \n 1044 \nFinally, the cauDon raised by our present work here is that in the classic study of saccade 1045 \ntasks, we may have generally assumed that the fixaDon spot was not influenDal. However, it 1046 \nclearly maiers. While we believe that the foveal bursts that we observed are not direct 1047 \nresponses to fixaDon spot removal in our tasks, it is sDll imperaDve to next ask whether they 1048 \nwould conDnue to happen when there is no foveal sensory transient. For example, one could 1049 \nuse a more abstract go instrucDon (that is also not represented foveally). One possibility 1050 \ncould be to maintain the fixaDon spot visible throughout the trials, and instead use a subtle 1051 \nspaDally-uninformaDve auditory cue as the instrucDon to generate a saccade. Under certain 1052 \ncircumstances, such sounds only minimally affect visually-driven effects (Malevich et al., 1053 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 28 \n2026), and as long as they do not drive foveal SC neurons, one can record from the foveal SC 1054 \nand check whether the foveal bursts that we observed would sDll happen. 1055 \n 1056 \n 1057 \n 1058 \nAcknowledgements 1059 \n 1060 \nWe were funded by the German Research AssociaDon (Deutsche Forschungsgemeinschah; 1061 \nDFG) under the Special Priority Programme “SPP 2411 Sensing LOOPS” (project numbers 1062 \n520617944, 520283985; HA6749/11-1). We were also supported by the DFG-funded 1063 \nInternaDonal Research Training Group IRTG2804. 1064 \n 1065 \n 1066 \n 1067 \nCompe3ng interests statement 1068 \n 1069 \nThe authors declare no compeDng interests. 1070 \n 1071 \n 1072 \n 1073 \nReferences 1074 \n 1075 \n 1076 \n 1077 \nAizawa H, Kobayashi Y , Yamamoto M, Isa T (1999) InjecDon of nicoDne into the superior 1078 \ncolliculus facilitates occurrence of express saccades in monkeys. J Neurophysiol 1079 \n82:1642-1646. 1080 \nAyar EC, Heusser MR, Bourrelly C, Gandhi NJ (2023) DisDnct context- and content-dependent 1081 \npopulaDon codes in superior colliculus during sensaDon and acDon. Proc Natl Acad 1082 \nSci U S A 120:e2303523120. 1083 \nBaumann MP , Bogadhi AR, Denninger AF, Hafed ZM (2023) Sensory tuning in neuronal 1084 \nmovement commands. Proc Natl Acad Sci U S A 120:e2305759120. 1085 \nBell AH, Meredith MA, Van Opstal AJ, Munoz DP (2006) SDmulus intensity modifies saccadic 1086 \nreacDon Dme and visual response latency in the superior colliculus. Exp Brain Res 1087 \n174:53-59. 1088 \nBoehnke SE, Munoz DP (2008) On the importance of the transient visual response in the 1089 \nsuperior colliculus. Curr Opin Neurobiol 18:544-551. 1090 \nBogadhi AR, Hafed ZM (2023) Express detecDon of visual objects by primate superior 1091 \ncolliculus neurons. ScienDfic reports 13:21730. 1092 \nBourrelly C, Massot C, Gandhi NJ (2023) Rapid Input-Output TransformaDon between Local 1093 \nField PotenDal and Spiking AcDvity during SensaDon but not AcDon in the Superior 1094 \nColliculus. J Neurosci 43:4047-4061. 1095 \nBuonocore A, Hafed ZM (2023) The inevitability of visual interrupDon. J Neurophysiol 1096 \n130:225-237. 1097 \nBuonocore A, Tian X, Khademi F, Hafed ZM (2021) Instantaneous movement-unrelated 1098 \nmidbrain acDvity modifies ongoing eye movements. eLife 10. 1099 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 29 \nCerkevich CM, Lyon DC, Balaram P , Kaas JH (2014) DistribuDon of corDcal neurons projecDng 1100 \nto the superior colliculus in macaque monkeys. Eye and brain 2014:121-137. 1101 \nChen CY , Hafed ZM (2017) A neural locus for spaDal-frequency specific saccadic suppression 1102 \nin visual-motor neurons of the primate superior colliculus. J Neurophysiol 117:1657-1103 \n1673. 1104 \nChen CY , Hafed ZM (2018) OrientaDon and Contrast Tuning ProperDes and Temporal Flicker 1105 \nFusion CharacterisDcs of Primate Superior Colliculus Neurons. Front Neural Circuits 1106 \n12:58. 1107 \nChen CY , Ignashchenkova A, Thier P , Hafed ZM (2015) Neuronal Response Gain Enhancement 1108 \nprior to Microsaccades. Curr Biol 25:2065-2074. 1109 \nChen CY , Hoffmann KP , Distler C, Hafed ZM (2019) The Foveal Visual RepresentaDon of the 1110 \nPrimate Superior Colliculus. Curr Biol 29:2109-2119 e2107. 1111 \nChen CY , Sonnenberg L, Weller S, Witschel T, Hafed ZM (2018) SpaDal frequency sensiDvity in 1112 \nmacaque midbrain. Nat Commun 9:2852. 1113 \nCho SH, Crapse T, Grimaldi P , Lau H, Basso MA (2021) Variable StaDsDcal Structure of 1114 \nNeuronal Spike Trains in Monkey Superior Colliculus. J Neurosci 41:3234-3253. 1115 \nCynader M, Berman N (1972) RecepDve-field organizaDon of monkey superior colliculus. J 1116 \nNeurophysiol 35:187-201. 1117 \nDorris MC, Munoz DP (1995) A neural correlate for the gap effect on saccadic reacDon Dmes 1118 \nin monkey. Journal of neurophysiology 73:2558-2562. 1119 \nDorris MC, Pare M, Munoz DP (1997) Neuronal acDvity in monkey superior colliculus related 1120 \nto the iniDaDon of saccadic eye movements. The Journal of neuroscience : the official 1121 \njournal of the Society for Neuroscience 17:8566-8579. 1122 \nDorris MC, Olivier E, Munoz DP (2007) CompeDDve integraDon of visual and preparatory 1123 \nsignals in the superior colliculus during saccadic programming. The Journal of 1124 \nneuroscience : the official journal of the Society for Neuroscience 27:5053-5062. 1125 \nEverling S, Pare M, Dorris MC, Munoz DP (1998) Comparison of the discharge characterisDcs 1126 \nof brain stem omnipause neurons and superior colliculus fixaDon neurons in monkey: 1127 \nimplicaDons for control of fixaDon and saccade behavior. J Neurophysiol 79:511-528. 1128 \nEverling S, Dorris MC, Klein RM, Munoz DP (1999) Role of primate superior colliculus in 1129 \npreparaDon and execuDon of anD-saccades and pro-saccades. J Neurosci 19:2740-1130 \n2754. 1131 \nFindlay JM (1982) Global visual processing for saccadic eye movements. Vision Res 22:1033-1132 \n1045. 1133 \nFindlay JM, Walker R (1999) A model of saccade generaDon based on parallel processing and 1134 \ncompeDDve inhibiDon. Behav Brain Sci 22:661-674; discussion 674-721. 1135 \nGoldberg ME, Wurtz RH (1972a) AcDvity of superior colliculus in behaving monkey. II. Effect 1136 \nof aienDon on neuronal responses. J Neurophysiol 35:560-574. 1137 \nGoldberg ME, Wurtz RH (1972b) AcDvity of superior colliculus in behaving monkey. I. Visual 1138 \nrecepDve fields of single neurons. J Neurophysiol 35:542-559. 1139 \nGoossens HH, van Opstal AJ (2012) OpDmal control of saccades by spaDal-temporal acDvity 1140 \npaierns in the monkey superior colliculus. PLoS computaDonal biology 8:e1002508. 1141 \nGrimaldi P , Cho SH, Lau H, Basso MA (2018) Superior colliculus signals decisions rather than 1142 \nconfidence: analysis of single neurons. J Neurophysiol 120:2614-2629. 1143 \nHafed ZM (2025) Superior colliculus peri-saccadic field potenDals are dominated by a visual 1144 \nsensory preference for the upper visual field. iScience 28:112021. 1145 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 30 \nHafed ZM, Krauzlis RJ (2008) Goal representaDons dominate superior colliculus acDvity 1146 \nduring extrafoveal tracking. J Neurosci 28:9426-9439. 1147 \nHafed ZM, Krauzlis RJ (2012) Similarity of superior colliculus involvement in microsaccade 1148 \nand saccade generaDon. J Neurophysiol 107:1904-1916. 1149 \nHafed ZM, Chen CY (2016) Sharper, Stronger, Faster Upper Visual Field RepresentaDon in 1150 \nPrimate Superior Colliculus. Curr Biol 26:1647-1658. 1151 \nHafed ZM, Hoffmann KP , Chen CY , Bogadhi AR (2023) Visual FuncDons of the Primate 1152 \nSuperior Colliculus. Annu Rev Vis Sci 9:361-383. 1153 \nHafed ZM, Chen CY , Tian X, Baumann M, Zhang T (2021) AcDve vision at the foveal scale in 1154 \nthe primate superior colliculus. J Neurophysiol. 1155 \nHeusser MR, Jagadisan UK, Gandhi NJ (2023) Drihing populaDon dynamics with transient 1156 \nresets characterize sensorimotor transformaDon in the monkey superior colliculus. 1157 \nbioRxiv. 1158 \nHikosaka O, Wurtz RH (1983) Visual and oculomotor funcDons of monkey substanDa nigra 1159 \npars reDculata. I. RelaDon of visual and auditory responses to saccades. J 1160 \nNeurophysiol 49:1230-1253. 1161 \nHumphrey NK (1968) Responses to visual sDmuli of units in the superior colliculus of rats and 1162 \nmonkeys. Exp Neurol 20:312-340. 1163 \nIsa T, Hall WC (2009) Exploring the superior colliculus in vitro. Journal of neurophysiology 1164 \n102:2581-2593. 1165 \nJagadisan UK, Gandhi NJ (2022) PopulaDon temporal structure supplements the rate code 1166 \nduring sensorimotor transformaDons. Current Biology 32:1010-1025. 1167 \nLi X, Basso MA (2005) CompeDDve sDmulus interacDons within single response fields of 1168 \nsuperior colliculus neurons. J Neurosci 25:11357-11373. 1169 \nLi X, Kim B, Basso MA (2006) Transient pauses in delay-period acDvity of superior colliculus 1170 \nneurons. J Neurophysiol 95:2252-2264. 1171 \nLund RD (1972) SynapDc paierns in the superficial layers of the superior colliculus of the 1172 \nmonkey, Macaca mulaia. Exp Brain Res 15:194-211. 1173 \nMalevich T, Baumann MP , Yu Y , Hafed ZM (2026) Vision dominates sound in mediaDng classic 1174 \ncue-induced microsaccadic eye movement modulaDons in rhesus macaque monkeys. 1175 \nJournal of Neurophysiology 135:777-796. 1176 \nMarino RA, Levy R, Munoz DP (2015) Linking express saccade occurance to sDmulus 1177 \nproperDes and sensorimotor integraDon in the superior colliculus. J Neurophysiol 1178 \n114:879-892. 1179 \nMarino RA, Trappenberg TP , Dorris M, Munoz DP (2011) SpaDal InteracDons in the Superior 1180 \nColliculus Predict Saccade Behavior in a Neural Field Model. Journal of cogniDve 1181 \nneuroscience. 1182 \nMarino RA, Levy R, Boehnke S, White BJ, It L, Munoz DP (2012) Linking visual response 1183 \nproperDes in the superior colliculus to saccade behavior. Eur J Neurosci 35:1738-1184 \n1752. 1185 \nMassot C, Jagadisan UK, Gandhi NJ (2019) Sensorimotor transformaDon elicits systemaDc 1186 \npaierns of acDvity along the dorsoventral extent of the superior colliculus in the 1187 \nmacaque monkey. Commun Biol 2:287. 1188 \nMay PJ (2006) The mammalian superior colliculus: laminar structure and connecDons. Prog 1189 \nBrain Res 151:321-378. 1190 \nMohler CW, Wurtz RH (1976) OrganizaDon of monkey superior colliculus: intermediate layer 1191 \ncells discharging before eye movements. J Neurophysiol 39:722-744. 1192 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 31 \nMoren J, Shibata T, Doya K (2013) The mechanism of saccade motor paiern generaDon 1193 \ninvesDgated by a large-scale spiking neuron model of the superior colliculus. PLoS 1194 \nOne 8:e57134. 1195 \nMunoz DP , Wurtz RH (1993a) FixaDon cells in monkey superior colliculus. II. Reversible 1196 \nacDvaDon and deacDvaDon. J Neurophysiol 70:576-589. 1197 \nMunoz DP , Wurtz RH (1993b) FixaDon cells in monkey superior colliculus. I. CharacterisDcs of 1198 \ncell discharge. J Neurophysiol 70:559-575. 1199 \nMunoz DP , Wurtz RH (1995a) Saccade-related acDvity in monkey superior colliculus. II. 1200 \nSpread of acDvity during saccades. J Neurophysiol 73:2334-2348. 1201 \nMunoz DP , Wurtz RH (1995b) Saccade-related acDvity in monkey superior colliculus. I. 1202 \nCharacterisDcs of burst and buildup cells. J Neurophysiol 73:2313-2333. 1203 \nMunoz DP , Istvan PJ (1998) Lateral inhibitory interacDons in the intermediate layers of the 1204 \nmonkey superior colliculus. J Neurophysiol 79:1193-1209. 1205 \nMunoz DP , Dorris MC, Pare M, Everling S (2000) On your mark, get set: brainstem circuitry 1206 \nunderlying saccadic iniDaDon. Can J Physiol Pharmacol 78:934-944. 1207 \nNakahara H, Morita K, Wurtz RH, OpDcan LM (2006) Saccade-related spread of acDvity 1208 \nacross superior colliculus may arise from asymmetry of internal connecDons. J 1209 \nNeurophysiol 96:765-774. 1210 \nPhongphanphanee P , Marino RA, Kaneda K, Yanagawa Y , Munoz DP , Isa T (2014) DisDnct local 1211 \ncircuit properDes of the superficial and intermediate layers of the rodent superior 1212 \ncolliculus. Eur J Neurosci 40:2329-2343. 1213 \nSaito Y , Isa T (2003) Local excitatory network and NMDA receptor acDvaDon generate a 1214 \nsynchronous and bursDng command from the superior colliculus. J Neurosci 23:5854-1215 \n5864. 1216 \nSatel J, Wang Z, Trappenberg TP , Klein RM (2011) Modeling inhibiDon of return as short-term 1217 \ndepression of early sensory input to the superior colliculus. Vision Res 51:987-996. 1218 \nSchiller PH, Koerner F (1971) Discharge characterisDcs of single units in superior colliculus of 1219 \nthe alert rhesus monkey. J Neurophysiol 34:920-936. 1220 \nSchiller PH, Stryker M, Cynader M, Berman N (1974) Response characterisDcs of single cells 1221 \nin the monkey superior colliculus following ablaDon or cooling of visual cortex. J 1222 \nNeurophysiol 37:181-194. 1223 \nShinn M, Lee D, Murray JD, Seo H (2022) Transient neuronal suppression for exploitaDon of 1224 \nnew sensory evidence. Nat Commun 13:23. 1225 \nSDne GM, Trautmann EM, Jeurissen D, Shadlen MN (2023) A neural mechanism for 1226 \nterminaDng decisions. Neuron 111:2601-2613 e2605. 1227 \nTrappenberg TP , Dorris MC, Munoz DP , Klein RM (2001) A model of saccade iniDaDon based 1228 \non the compeDDve integraDon of exogenous and endogenous signals in the superior 1229 \ncolliculus. Journal of cogniDve neuroscience 13:256-271. 1230 \nTroienberg C, Yu Y , Zhang T, Baumann MP , Malevich T, Prasad S, Hafed ZM (2026) Much 1231 \nhigher covariaDon with foveaDon Dming by superior colliculus than primary visual 1232 \ncorDcal neuronal acDvity. iScience 29:115432. 1233 \nWhite BJ, Marino RA, Boehnke SE, It L, Theeuwes J, Munoz DP (2013) CompeDDve 1234 \nintegraDon of visual and goal-related signals on neuronal accumulaDon rate: a 1235 \ncorrelate of oculomotor capture in the superior colliculus. J Cogn Neurosci 25:1754-1236 \n1768. 1237 \nWilson ME, Toyne MJ (1970) ReDno-tectal and corDco-tectal projecDons in Macaca mulaia. 1238 \nBrain Res 24:395-406. 1239 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint \n\n 32 \nWolpert DM, Ghahramani Z, Jordan MI (1995) An internal model for sensorimotor 1240 \nintegraDon. Science 269:1880-1882. 1241 \nWurtz RH, Mohler CW (1976) Enhancement of visual responses in monkey striate cortex and 1242 \nfrontal eye fields. J Neurophysiol 39:766-772. 1243 \nZhang T, Bogadhi AR, Hafed ZM (2025) Foveal neurons of the monkey superior colliculus 1244 \nsignal trans-saccadic predicDon errors. PLOS Biology. 1245 \nZhang T, Malevich T, Baumann MP , Hafed ZM (2022) Superior colliculus saccade motor bursts 1246 \ndo not dictate movement kinemaDcs. Commun Biol 5:1222. 1247 \nZhang T, Tian X, Malevich T, Baumann MB, Hafed ZM (2026) Foveal acDon for the control of 1248 \nextrafoveal vision. BioRxiv. 1249 \nZheng YJ, Adams DL, Gentry TN, Dilbeck MD, Economides JR, Horton JC (2024) ReDnal Input 1250 \nto Macaque Superior Colliculus Derives from Branching Axons ProjecDng to the 1251 \nLateral Geniculate Nucleus. J Neurosci 44. 1252 \n 1253 \n 1254 \n.CC-BY 4.0 International licensemade available under a \n(which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is \nThe copyright holder for this preprintthis version posted April 8, 2026. ; https://doi.org/10.64898/2026.04.06.716792doi: bioRxiv preprint","source_license":"CC-BY-4.0","license_restricted":false}