-
Journal of Vision Feb 2021How are visual sensory representations that are acquired peripherally from a saccade target related to sensory representations generated foveally after the saccade? We...
How are visual sensory representations that are acquired peripherally from a saccade target related to sensory representations generated foveally after the saccade? We tested the hypothesis that, when the two representations are perceived to belong to the same object, the post-saccadic value tends to overwrite the pre-saccadic value. Participants executed a saccade to a colored target object, which sometimes changed during the saccade by ±15°, 30°, or 45° in color space. They were post-cued to report either the pre-saccadic or post-saccadic color in a continuous report procedure. Substantial overwriting of the pre-saccadic color by the post-saccadic color was observed. Moreover, the introduction of a brief post-saccadic blank interval (which disrupted the perception of object correspondence) led to a substantial reduction in overwriting. The results provide the first direct evidence for an object-mediated overwriting mechanism across saccades, in which post-saccadic values automatically replace pre-saccadic values.
Topics: Adolescent; Adult; Female; Humans; Male; Perceptual Masking; Saccades; Visual Perception; Young Adult
PubMed: 33538771
DOI: 10.1167/jov.21.2.3 -
Sensors (Basel, Switzerland) Jul 2021Saccadic electrooculograms are discrete biosignals that contain the instantaneous angular position of the human eyes as a response to saccadic visual stimuli. These...
Saccadic electrooculograms are discrete biosignals that contain the instantaneous angular position of the human eyes as a response to saccadic visual stimuli. These signals are essential to monitor and evaluate several neurological diseases, such as Spinocerebellar Ataxia type 2 (SCA2). For this, biomarkers such as peak velocity, latency and duration are computed. To compute these biomarkers, we need to obtain the velocity profile of the signals using numerical differentiation methods. These methods are affected by the noise present in the electrooculograms, specially in subjects that suffer neurological diseases. This noise complicates the comparison of the differentiation methods using real saccadic signals because of the impossibility of establishing exact saccadic onset and offset points. In this work, we evaluate 16 differentiation methods by the design of an experiment that uses synthetic saccadic electrooculograms generated from parametric models of both healthy subjects and subjects suffering from Spinocerebellar Ataxia type 2 (SCA2). For these synthetic electrooculograms the exact velocity profile is known, hence we can use them as a reference for comparison and error computing for the tasks of saccade identification and saccade biomarker computing. Finally, we identify the best fitting method or methods for each evaluated task.
Topics: Electrooculography; Humans; Saccades
PubMed: 34372261
DOI: 10.3390/s21155021 -
Journal of Vision Jun 2020Visual crowding-the deleterious influence of nearby objects on object recognition-is considered to be a major bottleneck for object recognition in cluttered...
Visual crowding-the deleterious influence of nearby objects on object recognition-is considered to be a major bottleneck for object recognition in cluttered environments. Although crowding has been studied for decades with static and artificial stimuli, it is still unclear how crowding operates when viewing natural dynamic scenes in real-life situations. For example, driving is a frequent and potentially fatal real-life situation where crowding may play a critical role. In order to investigate the role of crowding in this kind of situation, we presented observers with naturalistic driving videos and recorded their eye movements while they performed a simulated driving task. We found that the saccade localization on pedestrians was impacted by visual clutter, in a manner consistent with the diagnostic criteria of crowding (Bouma's rule of thumb, flanker similarity tuning, and the radial-tangential anisotropy). In order to further confirm that altered saccadic localization is a behavioral consequence of crowding, we also showed that crowding occurs in the recognition of cluttered pedestrians in a more conventional crowding paradigm. We asked participants to discriminate the gender of pedestrians in static video frames and found that the altered saccadic localization correlated with the degree of crowding of the saccade targets. Taken together, our results provide strong evidence that crowding impacts both recognition and goal-directed actions in natural driving situations.
Topics: Adult; Automobile Driving; Crowding; Eye Movements; Female; Humans; Male; Pattern Recognition, Visual; Recognition, Psychology; Saccades; Visual Perception; Young Adult
PubMed: 32492098
DOI: 10.1167/jov.20.6.1 -
Journal of Neurophysiology Apr 2019Motor responses are fundamentally spatial in their function and neural organization. However, studies of inhibitory motor control, focused on global stopping of all...
Motor responses are fundamentally spatial in their function and neural organization. However, studies of inhibitory motor control, focused on global stopping of all actions, have ignored whether inhibitory control can be exercised selectively for specific actions. We used a new approach to elicit and measure motor inhibition by asking human participants to either look at (select) or avoid looking at (inhibit) a location in space. We found that instructing a location to be avoided resulted in an inhibitory bias specific to that location. When compared with the facilitatory bias observed in the Look task, it differed significantly in both its spatiotemporal dynamics and its modulation of attentional processing. While action selection was evident in oculomotor system and interacted with attentional processing, action inhibition was evident mainly in the oculomotor system. Our findings suggest that action inhibition is implemented by spatially specific mechanisms that are separate from action selection. NEW & NOTEWORTHY We show that cognitive control of saccadic responses evokes separable action selection and inhibition processes. Both action selection and inhibition are represented in the saccadic system, but only action selection interacts with the attentional system.
Topics: Adult; Attention; Choice Behavior; Female; Humans; Male; Neural Inhibition; Psychomotor Performance; Saccades
PubMed: 30649975
DOI: 10.1152/jn.00726.2017 -
Journal of Neurophysiology Mar 2021A fundamental problem in motor control is the coordination of complementary movement types to achieve a common goal. As a common example, humans view moving objects...
A fundamental problem in motor control is the coordination of complementary movement types to achieve a common goal. As a common example, humans view moving objects through coordinated pursuit and saccadic eye movements. Pursuit is initiated and continuously controlled by retinal image velocity. During pursuit, eye position may lag behind the target. This can be compensated by the discrete execution of a catch-up saccade. The decision to trigger a saccade is influenced by both position and velocity errors, and the timing of saccades can be highly variable. The observed distributions of saccade frequency and trigger time remain poorly understood, and this decision process remains imprecisely quantified. Here, we propose a predictive, probabilistic model explaining the decision to trigger saccades during pursuit to foveate moving targets. In this model, expected position error and its associated uncertainty are predicted through Bayesian inference across noisy, delayed sensory observations (Kalman filtering). This probabilistic prediction is used to estimate the confidence that a saccade is needed (quantified through log-probability ratio), triggering a saccade upon accumulating to a fixed threshold. The model qualitatively explains behavioral observations on the frequency and trigger time distributions of saccades during pursuit over a range of target motion trajectories. Furthermore, this model makes novel predictions that saccade decisions are highly sensitive to uncertainty for small predicted position errors, but this influence diminishes as the magnitude of predicted position error increases. We suggest that this predictive, confidence-based decision-making strategy represents a fundamental principle for the probabilistic neural control of coordinated movements. This is the first stochastic dynamical systems model of pursuit-saccade coordination accounting for noise and delays in the sensorimotor system. The model uses Bayesian inference to predictively estimate visual motion, triggering saccades when confidence in predicted position error accumulates to a threshold. This model explains saccade frequency and trigger time distributions across target trajectories and makes novel predictions about the influence of sensory uncertainty in saccade decisions during pursuit.
Topics: Bayes Theorem; Decision Making; Forecasting; Humans; Models, Neurological; Motion Perception; Photic Stimulation; Pursuit, Smooth; Saccades; Stochastic Processes
PubMed: 33356899
DOI: 10.1152/jn.00492.2019 -
Vision Research Jul 2022Visual stability across saccades requires us to discriminate self-generated motion by eye movements from motion occurring in the external world. In the laboratory visual...
Visual stability across saccades requires us to discriminate self-generated motion by eye movements from motion occurring in the external world. In the laboratory visual stability is often studied by asking observers to discriminate the direction of trans-saccadic target displacements. It is a well established finding that in this paradigm performance is usually very poor. If observers are insensitive to the intra-saccadic motion and see the pre- and the post-saccadic target in one location, one of both targets should be reported as shifted when observers would localize them. Here, I asked participants to perform a saccade to a target. During saccade execution the target was displaced either in backward or forward direction. After finishing the saccade, subjects had to report the position of either the pre-or the post-saccadic target. I found that subjects mislocalized the pre-saccadic target to the physical position of the post-saccadic target. This mislocalization occurred only after backward but not after forward displacements.
Topics: Eye Movements; Humans; Motion; Saccades
PubMed: 35248889
DOI: 10.1016/j.visres.2022.108023 -
Proceedings of the National Academy of... Feb 2021Perceptual stability is facilitated by a decrease in visual sensitivity during rapid eye movements, called saccadic suppression. While a large body of evidence...
Perceptual stability is facilitated by a decrease in visual sensitivity during rapid eye movements, called saccadic suppression. While a large body of evidence demonstrates that saccadic programming is plastic, little is known about whether the perceptual consequences of saccades can be modified. Here, we demonstrate that saccadic suppression is attenuated during learning on a standard visual detection-in-noise task, to the point that it is effectively silenced. Across a period of 7 days, 44 participants were trained to detect brief, low-contrast stimuli embedded within dynamic noise, while eye position was tracked. Although instructed to fixate, participants regularly made small fixational saccades. Data were accumulated over a large number of trials, allowing us to assess changes in performance as a function of the temporal proximity of stimuli and saccades. This analysis revealed that improvements in sensitivity over the training period were accompanied by a systematic change in the impact of saccades on performance-robust saccadic suppression on day 1 declined gradually over subsequent days until its magnitude became indistinguishable from zero. This silencing of suppression was not explained by learning-related changes in saccade characteristics and generalized to an untrained retinal location and stimulus orientation. Suppression was restored when learned stimulus timing was perturbed, consistent with the operation of a mechanism that temporarily reduces or eliminates saccadic suppression, but only when it is behaviorally advantageous to do so. Our results indicate that learning can circumvent saccadic suppression to improve performance, without compromising its functional benefits in other viewing contexts.
Topics: Adolescent; Adult; Female; Humans; Learning; Male; Middle Aged; Photic Stimulation; Saccades; Time Factors; Visual Perception; Young Adult
PubMed: 33526665
DOI: 10.1073/pnas.2012937118 -
Scientific Reports Jan 2018How the visual system achieves perceptual stability across saccadic eye movements is a long-standing question in neuroscience. It has been proposed that an efference...
How the visual system achieves perceptual stability across saccadic eye movements is a long-standing question in neuroscience. It has been proposed that an efference copy informs vision about upcoming saccades, and this might lead to shifting spatial coordinates and suppressing image motion. Here we ask whether these two aspects of visual stability are interdependent or may be dissociated under special conditions. We study a memory-guided double-step saccade task, where two saccades are executed in quick succession. Previous studies have led to the hypothesis that in this paradigm the two saccades are planned in parallel, with a single efference copy signal generated at the start of the double-step sequence, i.e. before the first saccade. In line with this hypothesis, we find that visual stability is impaired during the second saccade, which is consistent with (accurate) efference copy information being unavailable during the second saccade. However, we find that saccadic suppression is normal during the second saccade. Thus, the second saccade of a double-step sequence instantiates a dissociation between visual stability and saccadic suppression: stability is impaired even though suppression is strong.
Topics: Adult; Female; Humans; Male; Memory; Saccades; Visual Perception
PubMed: 29321562
DOI: 10.1038/s41598-017-18554-w -
Proceedings. Biological Sciences Mar 2023How does the brain maintain an accurate visual representation of external space? Movement errors following saccade execution provide sufficient information to...
How does the brain maintain an accurate visual representation of external space? Movement errors following saccade execution provide sufficient information to recalibrate motor and visual space. Here, we asked whether spatial information for vision and saccades is processed in shared or in separate resources. We used saccade adaptation to modify both, saccade amplitudes and visual mislocalization. After saccade adaptation was induced, we compared participants' saccadic and perceptual localization before and after we inserted 'no error' trials. In these trials, we clamped the post-saccadic error online to the predicted endpoints of saccades. In separate experiments, we either annulled the retinal or the prediction error. We also varied the number of 'no error' trials across conditions. In all conditions, we found that saccade adaptation remained undisturbed by the insertion of 'no error' trials. However, mislocalization decreased as a function of the number of trials in which zero retinal error was displayed. When the prediction error was clamped to zero, no mislocalization was observed at all. The results demonstrate the post-saccadic error is used separately to recalibrate visual and saccadic space.
Topics: Humans; Saccades; Acclimatization; Brain; Movement; Retina
PubMed: 36855869
DOI: 10.1098/rspb.2022.2566 -
Journal of Vision Aug 2021Trans-saccadic memory consists of keeping track of objects' locations and features across saccades; pre-saccadic information is remembered and compared with...
Trans-saccadic memory consists of keeping track of objects' locations and features across saccades; pre-saccadic information is remembered and compared with post-saccadic information. It has been shown to have limited resources and involve attention with respect to the selection of objects and features. In support, a previous study showed that recognition of distinct post-saccadic objects in the visual scene is impaired when pre-saccadic objects are relevant and thus already encoded in memory (Poth, Herwig, Schneider, 2015). Here, we investigated the inverse (i.e. how the memory of pre-saccadic objects is affected by abrupt but irrelevant changes in the post-saccadic visual scene). We also modulated the amount of attention to the relevant pre-saccadic object by having participants either make a saccade to it or elsewhere and observed that pre-saccadic attentional facilitation affected how much post-saccadic changes disrupted trans-saccadic memory of pre-saccadic objects. Participants identified a flashed symbol (d, b, p, or q, among distracters), at one of six placeholders (figures "8") arranged in circle around fixation while planning a saccade to one of them. They reported the identity of the symbol after the saccade. We changed the post-saccadic scene in Experiment one by removing the entire scene, only the placeholder where the pre-saccadic symbol was presented, or all other placeholders except this one. We observed reduced identification performance when only the saccade-target placeholder disappeared after the saccade. In Experiment two, we changed one placeholder location (inward/outward shift or rotation re. saccade vector) after the saccade and observed that identification performance decreased with increased shift/rotation of the saccade-target placeholder. We conclude that pre-saccadic memory is disrupted by abrupt attention-capturing post-saccadic changes of visual scene, particularly when these changes involve the object prioritized by being the goal of a saccade. These findings support the notion that limited trans-saccadic memory resources are disrupted when object correspondence at saccadic goal is broken through removal or location change.
Topics: Humans; Saccades
PubMed: 34347017
DOI: 10.1167/jov.21.8.8