Biology subjects

Ohl, S.

Publications and source records attributed to Ohl, S..

10 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.

neuroscience↗

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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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

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

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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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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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

Visual short-term memory related EEG components in a virtual reality setup

Virtual reality (VR) offers a powerful tool for investigating cognitive processes, as it allows researchers to gauge behaviors and mental states in complex, yet highly controlled, scenarios. The use of VR head-mounted displays in combination with physiological measures such as EEG presents new challenges and raises the question whether established findings also generalize to a VR setup. Here, we used a VR headset to assess the spatial constraints underlying two well-established EEG correlates of visual short-term memory: the amplitude of the contralateral delay activity (CDA) and the lateralization of induced alpha power during memory retention. We tested observers visual memory in a delayed match-to-sample task with bilateral stimulus arrays of either two or four items while varying the horizontal eccentricity of the memory arrays (4, 9, or 14 degrees of visual angle). The CDA amplitude differed between high and low memory load at the two smaller eccentricities, but not at the largest eccentricity. Neither memory load nor eccentricity significantly influenced the observed alpha lateralization. We further fitted time-resolved spatial filters to decode memory load from the event-related potential as well as from its time-frequency decomposition. Classification performance during the retention interval was above chance level for both approaches and did not vary significantly across eccentricities. We conclude that commercial VR hardware can be utilized to study the CDA and lateralized alpha power, and we provide caveats for future studies targeting these EEG markers of visual memory in a VR setup. Impact statementCombining EEG with virtual reality, we studied how the eccentricity of a memory array during encoding affects well-known neural markers of visual short-term memory. We reveal that the previously reported occurrence of these EEG components during visual memory retention can be replicated in such a setup. These EEG markers were differently affected by eccentricity, hence providing valuable constraints for future experimental designs.

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bioRxiv2018

Active vision varies across the cardiac cycle

Perception and cognition oscillate with fluctuating bodily states. For example, visual processing has been shown to change with alternating cardiac phases. Here, we study the heartbeats role for active information sampling--testing whether humans implicitly act upon their environment so that relevant signals appear during preferred cardiac phases. During the encoding period of a visual memory experiment, participants clicked through a set of emotional pictures to memorize them for a later recognition test. By self-paced key press, they actively prompted the onset of shortly (100-ms) presented pictures. Simultaneously recorded electrocardiograms allowed us to analyse the self-initiated picture onsets relative to the heartbeat. We find that self-initiated picture onsets vary across the cardiac cycle, showing an increase during cardiac systole, while memory performance was not affected by the heartbeat. We conclude that active information sampling integrates heart-related signals, thereby extending previous findings on the association between body-brain interactions and behaviour.

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