Biology subjects

Rolfs, M.

Publications and source records attributed to Rolfs, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Space-based and object-based saccadic selection in visual working memory

Saccades made during memory maintenance prioritize memory for the saccade target, but it is unclear if this benefit is specific to a location or extends across memorized objects. In three experiments, we examined whether saccadic selection spreads to other locations within the same object. In Experiment 1, we asked observers to remember three oriented Gabors presented either within contour-defined objects or without object structure. A subsequent movement cue prompted observers to move their eyes to the indicated location. We then probed memory for stimuli at locations equidistant from the saccade target, in either the same or a different object. Memory was best for stimuli at locations congruent with the saccade target, and consistently weaker for other stimuli presented in the same or a different object than the saccade target. In Experiment 2, we created more complex objects by adding more object features to the stimulus. Again, memory performance was best for stimuli congruent with the saccade target location, whereas memory in incongruent trials was worse and similar for stimuli in the same and different object as the saccade target. In Experiment 3, we tested if saccadic selection is present and propagates within the object in a change detection task. Again, memory performance (i.e., change detection) was best at the saccade target location. However, this memory benefit also spread to other locations within the same object. Our results imply that saccadic selection in visual working memory is primarily space-based but can also spread towards locations within the object where a saccade was directed.

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bioRxiv2026

The Spatial Specificity and Recovery from Visual Adaptation in Causality Perception

When one object approaches another object which, upon touching, moves in the same direction, humans report a vivid impression of one launching the other. Visual adaptation can alter this perception of causality: observers less often report seeing a launch after viewing a stream of launch events. In three experiments, we further characterised how visual adaptation influences the perception of causality by determining the spatial specificity of adaptation and timecourse of recovery from adaptation. In Experiment 1, observers saw ambiguous test events (i.e., the overlap between the two objects varied over trials) at three different horizontal eccentricities. Adaptation was strongest when adaptor and test event were presented at the same eccentricity, and absent when the two were separated by just three degrees of visual angle. Moreover, the perception of causality gradually recovered from adaptation, but remained incomplete. In Experiment 2, both long and short adaptation sequences were highly effective in driving adaptation, and showed no difference in the recovery timecourse, which was complete following more experimental blocks. In Experiment 3, a break without any task-relevant visual input also led to a recovery over the same timespan, but this time, the recovery was instantaneous and incomplete. Altogether, our results provide evidence for highly spatially specific computations, instananeously responding to the onset of adaptation and then gradually recovering from the adaptation over a short time window.

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bioRxiv2026

Static masks and saccadic velocity profile jointly reduce perceived motion: Evidence from simulated saccades

Saccadic eye movements sweep the visual scene across the retina, yet the resulting motion is rarely perceived. Visual factors alone, such as the presence of static pre- and post-saccadic input, can attenuate motion perception, suggesting effective masking of the motion signal during early visual processing. Here, we isolated the visual component of this reduction in motion perception using simulated saccades presented to fixating observers. Across two experiments, we manipulated motion amplitude (6-18 dva), duration, and velocity profile and measured perceived amplitude and velocity at varying masking durations. Visual masking strongly reduced perceived motion amplitude and velocity, with short halftimes ([~]15 ms) that were largely invariant across saccade amplitudes. Critically, motion following a naturalistic saccadic velocity profile was perceived as shorter and slower than constant-velocity motion matched in amplitude and duration, even without explicit masking. This additional reduction increased with both amplitude and duration. These results show that visual mechanisms alone can account for substantial motion reduction across a wide range of amplitudes and demonstrate a partially separable contribution of the saccadic velocity profile, suggesting that the temporal structure of retinal motion itself supports perceptual continuity across eye movements.

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bioRxiv2025

In pursuit of saccade awareness: Limited control and minimal conscious access to catch-up saccades during smooth pursuit eye movements.

Observers use smooth pursuit to track moving objects--like koi carp gliding through a pond. When positional errors accumulate, rapid catch-up saccades correct for them. Despite their abruptness, these saccades usually go unnoticed, creating the seamless experience of smooth tracking. We conducted three experiments to examine awareness and control of catch-up saccades (Experiment 1), the effect of training (Experiment 2), and of movement intention (Experiment 3). All experiments followed a similar protocol. On each trial, a target moved horizontally at one of three constant speeds (3-12 dva/s). Two horizontal stimulus bands with vertically oriented gratings appeared above and below the trajectory. These bands were rendered invisible during pursuit by rapid phase shifts (>60 Hz), but became visible when briefly stabilized on the retina--either by a catch-up saccade or its replayed retinal consequence--providing immediate, saccade-contingent visual feedback. Observers reported whether they had seen the stimulus bands (visual sensitivity) and whether they were aware of making a catch-up saccade (saccade sensitivity). Visual sensitivity was consistently higher in trials with a catch-up saccade, confirming that these movements reduce retinal motion and enhance visibility. Higher target speeds increased saccade rate, but observers struggled to control them consciously: Visual feedback and training had no effect on the ability to control catch-up saccades. Only suppression-instructions yielded a small reduction. Saccade sensitivity was near zero, even in trials with saccade-contingent feedback. Neither training nor intention improved awareness. Together, our data suggest a limited ability to control and a low level of sensorimotor awareness of catch-up saccades during pursuit. Significance statementSmooth pursuit eye movements allow us to track moving objects seamlessly, yet these movements are frequently interrupted by small, rapid corrective catch-up saccades. Despite their disruptive nature, observers rarely notice their own catch-up saccades. To address this conundrum, we used a novel paradigm employing a stimulus that remains invisible during pursuit but becomes visible when retinally stabilized by a catch-up saccade--providing saccade-contingent visual feedback to investigate conscious control and awareness of catch-up saccades during pursuit. Our data show that higher target speeds increased saccade rates, and observers were largely unable to modulate this rate--except for a slight reduction when explicitly instructed to pursue as smoothly as possible. Moreover, awareness remained low even with saccade-contingent feedback, and neither training nor intention improved it. Together, these findings suggest limited conscious control and low sensorimotor awareness of catch-up saccades during smooth pursuit.

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bioRxiv2025

High-fidelity, but hypometric spatial localization of afterimages across saccades

Humans typically perceive their visual world as stable and continuous, despite frequent shifts of the retinotopic reference frame caused by saccades. This visual stability is paralleled by afterimage movement across saccades: Although retinotopically stable, afterimages appear to move in egocentric space wherever the eye moves. To investigate the mechanisms underlying this phenomenon, we tasked human observers to localize afterimages relative to briefly flashed probes in complete darkness. This psychophysical tracking of afterimages was accompanied by eye tracking, allowing us to fit a dedicated computational model to accurately predict afterimage movement based on the size of eye movements. The gain of afterimage movement was significantly hypometric, remained unaffected by post-saccadic visual feedback and saccadic adaptation, and was inversely related to saccade gain. These findings suggest that afterimage movement is driven by efference-based, feedforward prediction of visual consequences of saccades and demonstrate the potential of the afterimage-tracking technique for studying visual stability. SignificanceIn low-light environments, brief high-intensity visual stimulation can induce long-lasting retinal afterimages. When observers then make eye movements to explore their visual environment, these afterimages - albeit fixed in the retinotopic frame of reference - appear to move in egocentric space wherever the eye moves. Even though this phenomenon has been known for centuries, the underlying computations remained unexplained. Tracking eye and afterimage positions simultaneously, we found that perceived afterimage position was accurately predicted by eye position across a variety of visuomotor conditions, whereby the eye movements size was however systematically underestimated by the visual system. Considering a parsimonious model of visual localization, afterimage movement can be understood as a consequence of feedforward predictions of the visual consequences of impending eye movements.

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bioRxiv2025

Microsaccades do not give rise to a conscious feeling of agency for their sensorimotor consequences in visual perception.

Feeling of agency (FoA)--the experience of controlling ones actions and their outcomes--has been widely studied for bodily movements. Here, we investigated if microsaccades--small ballistic eye movements--are equally characterized by FoA and if intention mediates this sense of control. We measured FoA via intentional binding, a perceived compression between an action and its effect. In our experiments, we presented a vertically oriented grating, rendered invisible during stable fixation by a rapid temporal phase shift (>60 Hz) that became visible when its retinal motion was slowed down by a microsaccade (active condition). The stimulus was embedded in a clock face and observers reported perceived stimulus timing in each trial. Perceived timing of microsaccade-contingent stimulus perception was compared to the replay of a previous microsaccades retinal consequence (replay condition). Trials without a stimulus were included as a control. To examine the role of intention, we tested this paradigm across two experiments in which observers were either instructed to saccade (intended microsaccades) or fixate (unintended microsaccades). In Experiment 2, no instruction was administered such that any microsaccades were considered spontaneous. Microsaccades--either actively generated or replayed-- consistently rendered the stimulus highly visible compared to trials without such movements-- provided microsaccade direction and peak velocity aligned with the stimuluss motion. Temporal estimates did not differ between the active and replay conditions for any microsaccade type. This result suggests the absence of temporal binding between eye movements and their sensory consequences, and that intention does not facilitate FoA for small eye movements. Significance statementEye movements reflect our decision to closer inspect an aspect of the environment--bodily actions that align our perception with a preceding intention. Here, we investigated if microsaccades--a ballistic, minuscule type of saccade--can be characterized by a feeling of agency: the faint experience of affecting change through intentional actions. In two experiments, we presented an identical stimulus whose visibility was either gaze-contingent (active condition) or independent of eye movements (replay condition). In Experiment 1, we directly compared intended and unintended microsaccades and contrasted them with spontaneous microsaccades in Experiment 2. We found no difference between the active and replay condition for either eye movement type. Our data, hence, does not support feeling of agency for microsaccades. While it remains an open question if large saccades are characterized by feeling of agency, our finding demonstrates that intention is not sufficient to elicit feeling of agency for minuscule motor acts.

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bioRxiv2025

Early visual signatures and benefits of intra-saccadic motion streaks

Eye movements routinely induce motion streaks as they shift visual projections across the retina at high speeds. To investigate the visual consequences of intra-saccadic motion streaks, we co-registered eye tracking and EEG while gaze-contingently shifting target objects during saccades, presenting either continuous, streaky or apparent, step-like motion in four directions. We found significant reductions of secondary saccade latency, as well as improved decoding of the post-saccadic target location from the EEG signal when motion streaks were available. These signals arose as early as 50 ms after saccade offset and had a clear occipital topography. Using a physiologically plausible visual processing model, we provide evidence that the targets motion trajectory is coded in orientation-selective channels and that speed of gaze correction was linked to the visual dynamics arising from the combination of saccadic and target motion, providing a parsimonious explanation of the behavioral benefits of intra-saccadic motion streaks.

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bioRxiv2025

Putting causality into context: Causal capture escapes the visual adaptation of causality

Results from psychophysical studies using visual adaptation suggest that launch detectors in the visual system underlie the perception of causality in simple visual events. These detectors respond to events in which one stimulus collides with another stimulus (i.e., a launch), and do not respond to events where one stimulus passes over another (i.e., a pass). Prolonged visual adaptation to launches significantly reduces observers propensity to see causal launches at the same retinotopic location. This finding could be taken to indicate that launch detectors are necessary for the local detection of causal launches. However, contextual events--that are spatially separated from the test event location--shift observers perception of a causal relation in the direction of the type of contextual event (Scholl & Nakayama, 2002), providing evidence for spatial integration beyond a specific retinotopic location. Here, we used visual adaptation as a tool to investigate whether the contextual influence on causal perception relies on local launch detectors. Before and after adaptation, we determined the proportion of reported launches in ambiguous test events in the presence of no context, launch context, and pass context events. We hypothesized that if the contextual influence relies on (unadapted) local launch detectors, then visual adaptation should affect the contextual influence on causal perception. Before adaptation, a launch-context event increased the proportion of reported launches (while a pass context event decreased it). Visual adaptation to launches significantly decreased the proportion of reported launches in no-context trials, but did not affect perceptual reports in no-context trials. In fact, contextual influences, expressed relative to no-context trials, emerged strongly after adaptation. This result suggests that context effects override strong negative aftereffects from adaptation, indicating that contextual influences operate at a level that bypasses the local launch detector at the adapted location.

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bioRxiv2025

Decoding peripheral saccade targets from foveal retinotopic cortex

Human vision is characterized by frequent eye movements and constant shifts in visual input, yet our perception of the world remains remarkably stable. Here, we directly demonstrate image-specific foveal feedback to primary visual cortex in the context of saccadic eye movements. To this end, we used a gaze-contingent fMRI paradigm, in which peripheral saccade targets disappeared before they could be fixated. Despite no direct foveal stimulation, we were able to decode peripheral saccade targets from foveal retinotopic areas, demonstrating that image-specific feedback during saccade preparation may underlie this effect. Decoding was sensitive to shape but not semantic category of natural images, indicating feedback of only low-to-mid-level information. Cross-decoding to a control condition with foveal stimulus presentation indicates a shared representational format between foveal feedback and direct stimulation. Moreover, eccentricity-dependent analyses showed a u-shaped decoding curve, confirming that these results are not explained by spillover of peripheral activity or large receptive fields. Finally, fluctuations in foveal decodability covaried with activity in the intraparietal sulcus, thus providing a candidate region for driving foveal feedback. These findings suggest that foveal cortex predicts the features of incoming stimuli through feedback from higher cortical areas, which offers a candidate mechanism underlying stable perception.

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bioRxiv2024

Sensorimotor awareness requires intention: Evidence from minuscule eye movements.

Microsaccades are tiny eye movements that are thought to occur spontaneously and without awareness but can also be intentionally controlled with high precision. We used these tiny visual actions to investigate how intention modulates sensorimotor awareness by directly comparing intended, unintended, and spontaneous microsaccades. In addition, we dissociated the effects of action intention and the actions visual consequences on awareness. In 80% of all trials, we presented a stimulus at high temporal frequency rendering it invisible during stable fixation. Critically, the stimulus became visible when a microsaccade in the same direction caused it to slow down on the retina (generated microsaccade condition; 40% of trials) or when the microsaccades visual consequence was replayed (replayed microsaccade condition; 40% of trials). Participants reported whether they perceived the stimulus (visual sensitivity), whether they believed they had made a microsaccade (microsaccade sensitivity), and their level of confidence that their eye movement behavior was linked to their perception (causality assignment). Visual sensitivity was high for both, generated and replayed microsaccades and comparable for intended, unintended, and spontaneous eye movements. Microsaccade sensitivity, however, was low for spontaneous microsaccades, but heightened for both intended and unintended eye movements, showing that the intention to saccade or fixate enhances awareness of otherwise undetected eye movements. Visual consequences failed to aid eye movement awareness, and confidence ratings revealed a poor understanding of a causal relationship between eye movement and sensory consequence. These findings highlight the functional relevance of intention in sensorimotor awareness at the smallest scale of visual actions. Significance statementWhile eye movements are among the most frequent human actions, they are rarely perceived consciously, despite causing sweeping changes in retinal inputs. Here investigate how intention can modulate awareness of even the smallest human actions: microsaccades. We developed a novel paradigm that allowed us to dissociate the role of action intention and an actions sensory consequence for awareness, two factors that previous research has typically confounded. Our data provide strong evidence that observers can detect small eye movements reliably and demonstrates that sensitivity towards microsaccades was neither driven by an eye movements motor component nor its visual consequences alone. Instead, we find that intention opens a gate to sensorimotor awareness, even for actions typically too small to be perceived.

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bioRxiv2024

An Information Processing Pattern from Robotics Predicts Properties of the Human Visual System

We tested the hypothesis that an algorithmic information processing pattern from robotics, Active InterCONnect (AICON), could serve as a useful representation for exploring human vision. We created AICON-based computational models for two visual illusions: the shape-contingent color aftereffect and silencing by motion. The models reproduced the effects seen in humans and generated surprising and novel predictions that we validated through human psychophysical experiments. Inconsistencies between model predictions and experimental results were resolved through iterative model adjustments. For the shape-contingent color aftereffect, the model predicted and experiments confirmed weaker aftereffects for outline shape manipulations and individual differences in perceived aftereffects. For silencing by motion, the model predicted and experiments validated unexpected trends as well as individual differences. Our findings demonstrate AICONs ability to capture relevant aspects of human visual information processing including variability across individuals. It highlights the potential for novel collaborations between synthetic and biological disciplines.

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bioRxiv2023

Visual routines for detecting causal interactions are tuned to motion direction

Detecting causal relations structures our perception of events in the world. Here, we determined for visual interactions whether generalized (i.e., feature-invariant) or specialized (i.e., feature-selective) visual routines underlie the perception of causality. To this end, we applied a visual adaptation protocol to assess the adaptability of specific features in classical launching events of simple geometric shapes. We asked observers to report whether they observed a launch or a pass in ambiguous test events (i.e., the overlap between two discs varied from trial to trial). After prolonged exposure to causal launch events (the adaptor) defined by a particular set of features (i.e., a particular motion direction, motion speed, or feature conjunction), observers were less likely to see causal launches in subsequent ambiguous test events than before adaptation. Crucially, adaptation was contingent on the causal impression in launches as demonstrated by a lack of adaptation in non-causal control events. We assessed whether this negative aftereffect transfers to test events with a new set of feature values that were not presented during adaptation. Processing in specialized (as opposed to generalized) visual routines predicts that the transfer of visual adaptation depends on the feature-similarity of the adaptor and the test event. We show that the negative aftereffects do not transfer to unadapted launch directions but do transfer to launch events of different speed. Finally, we used colored discs to assign distinct feature-based identities to the launching and the launched stimulus. We found that the adaptation transferred across colors if the test event had the same motion direction as the adaptor. In summary, visual adaptation allowed us to carve out a visual feature space underlying the perception of causality and revealed specialized visual routines that are tuned to a launchs motion direction. Significance statementWe used visual adaptation to carve out the visual feature space critical for detecting collisions in visual launching events. Observers were less likely to report perceiving a collision after the repeated viewing of one disc colliding with and launching the movement of another disc. Importantly, observers perception of collisions in the direction opposite to the adaptor remained unaffected. However, provided the test stimulus had the adapted direction of motion, the speed or the color of the objects involved in the launching event did not need to be the same as during adaptation for a negative aftereffect to occur. Thus, visual routines that detect causal interactions are selective for motion direction, providing evidence that the perception of causality in a visual interaction relies on low-level perceptual processes.

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bioRxiv2023

Lawful kinematics link eye movements to the limits of high-speed perception

Perception relies on active sampling of the environment. What part of the physical world can be sensed is limited by biophysical constraints of sensory systems, but might be further constrained by the kinematic bounds of the motor actions that acquire sensory information. We tested this fundamental idea for humans fastest and most frequent behavior--saccadic eye movements--which entails retinal motion that commonly escapes visual awareness. We discover that the visibility of a high-speed stimulus, presented during fixation, is predicted by the lawful sensorimotor contingencies that saccades routinely impose on the retina, reflecting even distinctive variability between observers movements. Our results suggest that the visual systems functional and implementational properties are best understood in the context of movement kinematics that impact its sensory surface.

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bioRxiv2023

The magnitude and time course of pre-saccadic foveal prediction depend on the conspicuity of the saccade target

We previously demonstrated that during the preparation of a large-scale saccadic eye movement, defining features of the eye movement target (i.e., its orientation) are anticipated in pre-saccadic foveal vision (Kroell & Rolfs, 2022). In this Research Advance, we show that the conspicuity of orientation information at the saccade target location influences the magnitude and time course of foveal enhancement. As in our previous study, observers prepared a saccade to a peripheral orientation signal (the target) while monitoring the appearance of a second orientation signal (the probe) in their pre-saccadic center of gaze. The probe appeared in 50% of trials and either had the same orientation as the target (congruent) or a different orientation (incongruent). In the current study, we manipulated the opacity of the target against the 1/f background noise in four logarithmic steps from 25% to 90%. An increase in opacity translated to an increase in luminance contrast and the signal-to-noise ratio of orientation information within the target region. We made three main observations: First, foveal Hit Rates for target-congruent and incongruent probes decreased as target opacity increased, presumably since attention was increasingly drawn to the target the more salient it became. Crucially, foveal enhancement defined as the difference between congruent and incongruent Hit Rates increased with opacity. Second, the time course of foveal enhancement showed an oscillatory pattern that was particularly pronounced at higher target opacities. Third, unlike the difference in Hit Rates, the difference in False Alarm Rates did not vary with opacity. Instead, reverse correlations suggest that at higher target opacities, False Alarms were increasingly triggered by signal, that is, by incidental orientation information in the foveal noise. Beyond providing new mechanistic insights into active foveal processing, these findings are relevant for researchers planning to adapt our paradigm to study related questions. Presenting the saccade target at a high signal-to-noise ratio appears beneficial as congruency effects, especially when time-resolved, are most robustly detectable.

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bioRxiv2023

Saccadic omission revisited: What saccade-induced smear looks like

During active visual exploration, saccadic eye movements rapidly shift the visual image across the human retina. Although these high-speed shifts occur at a high rate and introduce considerable amounts of motion smear during natural vision, our perceptual experience is oblivious to it. This saccadic omission, however, does not entail that saccadeinduced motion smear cannot be perceived in principle. Using tachistoscopic displays of natural scenes, we rendered saccade-induced smear highly conspicuous. By systematically manipulating peri-saccadic display durations we studied the dynamics of smear in a time-resolved manner, assessing identification performance of smeared scenes, as well as perceived smear amount and direction. Both measures showed distinctive, U-shaped time courses throughout the saccade, indicating that generation and reduction of perceived smear occurred during saccades. Moreover, low spatial frequencies and orientations parallel to the direction of the ongoing saccade were identified as the predominant visual features encoded in motion smear. We explain these findings using computational models that assume no more than saccadic velocity and human contrast sensitivity profiles, and present a motion-filter model capable of predicting observers perceived amount of smear based on their eyes trajectories, suggesting a direct link between perceptual and saccade dynamics. Replays of the visual consequences of saccades during fixation led to virtually identical results as actively making saccades, whereas the additional simulation of perisaccadic contrast suppression heavily reduced this similarity, providing strong evidence that no extra-retinal process was needed to explain our results. Saccadic omission of motion smear may be conceptualized as a parsimonious visual mechanism that emerges naturally from the interplay of retinal consequences of saccades and early visual processing.

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bioRxiv2023

Objects Guide Human Gaze Behavior in Dynamic Real-World Scenes

The complexity of natural scenes makes it challenging to experimentally study the mechanisms behind human gaze behavior when viewing dynamic environments. Historically, eye movements were believed to be driven primarily by space-based attention towards locations with salient features. Increasing evidence suggests, however, that visual attention does not select locations with high saliency but operates on attentional units given by the objects in the scene. We present a new computational framework to investigate the importance of objects for attentional guidance. This framework is designed to simulate realistic scanpaths for dynamic real-world scenes, including saccade timing and smooth pursuit behavior. Individual model components are based on psychophysically uncovered mechanisms of visual attention and saccadic decision-making. All mechanisms are implemented in a modular fashion with a small number of well-interpretable parameters. To systematically analyze the importance of objects in guiding gaze behavior, we implemented five different models within this framework: two purely spatial models, where one is based on low-level saliency and one on high-level saliency, two object-based models, with one incorporating low-level saliency for each object and the other one not using any saliency information, and a mixed model with object-based attention and selection but space-based inhibition of return. We optimized each models parameters to reproduce the saccade amplitude and fixation duration distributions of human scanpaths using evolutionary algorithms. We compared model performance with respect to spatial and temporal fixation behavior, including the proportion of fixations exploring the background, as well as detecting, inspecting, and returning to objects. A model with object-based attention and inhibition, which uses saliency information to prioritize between objects for saccadic selection, leads to scanpath statistics with the highest similarity to the human data. This demonstrates that scanpath models benefit from object-based attention and selection, suggesting that object-level attentional units play an important role in guiding attentional processing. Author summaryThere has long been an interest in understanding how we decide when and where to move our eyes, and psychophysical experiments have uncovered many underlying mechanisms. Under controlled laboratory conditions, objects in the scene play an important role in guiding our attention. Due to the visual complexity of the world around us, however, it is hard to assess experimentally how objects influence eye movements when observing dynamic real-world scenes. Computational models have proved to be a powerful tool for investigating visual attention, but existing models are either only applicable to images or restricted to predicting where humans look on average. Here, we present a computational framework for simulating where and when humans decide to move their eyes when observing dynamic real-world scenes. Using our framework, we can assess the influence of objects on the model predictions. We find that including object-based attention in the modeling increases the resemblance of simulated eye movements to human gaze behavior, showing that objects play indeed an important role in guiding our gaze when exploring the world around us. We hope that the availability of this framework encourages more research on attention in dynamic real-world scenes.

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bioRxiv2022

Foveal vision predictively sensitizes to defining features of eye movement targets

Despite the foveas singular importance for active human vision, the impact of large eye movements on foveal processing remains elusive. Building on findings from passive fixation tasks, we hypothesized that during the preparation of rapid eye movements (saccades), foveal processing anticipates soon-to-be fixated visual features. Using a dynamic large-field noise paradigm, we indeed demonstrate that sensitivity for defining features of a saccade target is enhanced in the pre-saccadic center of gaze. Enhancement manifested in higher Hit Rates for foveal probes with target-congruent orientation, and a sensitization to incidental, target-like orientation information in foveally presented noise. Enhancement was spatially confined to the center of gaze and its immediate vicinity. We suggest a crucial contribution of foveal processing to trans-saccadic visual continuity which has previously been overlooked: Foveal processing of saccade targets commences before the movement is executed and thereby enables a seamless transition once the center of gaze reaches the target.

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bioRxiv2021

Oculomotor freezing tracks perception and is immune to decision bias

The appearance of a salient stimulus rapidly inhibits saccadic eye movements. Curiously, this "oculomotor freezing" reflex is triggered only by stimuli that the observer reports seeing. It remains unknown, however, if oculomotor freezing is linked to the observers sensory experience, or their decision that a stimulus was present. To dissociate between these possibilities, we manipulated decision criterion via monetary payoffs and stimulus probability in a detection task. These manipulations greatly shifted observers decision criteria but did not affect the degree to which microsaccades were inhibited by stimulus presence. Moreover, the link between oculomotor freezing and explicit reports of stimulus presence was stronger when the criterion was conservative rather than liberal. We conclude that the sensory threshold for oculomotor freezing is independent of decision bias. Provided that conscious experience is also unaffected by such bias, oculomotor freezing is an implicit indicator of sensory awareness. New & NoteworthySometimes a visual stimulus reaches awareness, and sometimes it does not. To understand why, we need objective, bias-free measures of awareness. We discovered that a reflexive freezing of small eye movements indicates when an observer detects a stimulus. Furthermore, when we biased observers decisions to report seeing the stimulus, the oculomotor reflex was unaltered. This suggests that the threshold for conscious perception is independent of the decision criterion and is revealed by oculomotor freezing.

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