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Sensors (Basel, Switzerland) Feb 2024In this paper, we present and evaluate a calibration-free mobile eye-traking system. The system's mobile device consists of three cameras: an IR eye camera, an RGB eye...
In this paper, we present and evaluate a calibration-free mobile eye-traking system. The system's mobile device consists of three cameras: an IR eye camera, an RGB eye camera, and a front-scene RGB camera. The three cameras build a reliable corneal imaging system that is used to estimate the user's point of gaze continuously and reliably. The system auto-calibrates the device unobtrusively. Since the user is not required to follow any special instructions to calibrate the system, they can simply put on the eye tracker and start moving around using it. Deep learning algorithms together with 3D geometric computations were used to auto-calibrate the system per user. Once the model is built, a point-to-point transformation from the eye camera to the front camera is computed automatically by matching corneal and scene images, which allows the gaze point in the scene image to be estimated. The system was evaluated by users in real-life scenarios, indoors and outdoors. The average gaze error was 1.6∘ indoors and 1.69∘ outdoors, which is considered very good compared to state-of-the-art approaches.
Topics: Eye Movements; Fixation, Ocular; Eye-Tracking Technology; Cornea; Algorithms
PubMed: 38400392
DOI: 10.3390/s24041237 -
Journal of Neurophysiology Feb 2023Through the process of saccadic inhibition, visual events briefly suppress eye movements including microsaccades. In humans, saccadic inhibition has been shown to occur...
Through the process of saccadic inhibition, visual events briefly suppress eye movements including microsaccades. In humans, saccadic inhibition has been shown to occur in response to the presentation of parafoveal or peripheral visual distractors during fixation and target-directed saccades and to physical changes of behaviorally relevant visual objects. In monkeys performing tasks that controlled eye movements, saccadic inhibition of microsaccades and target-directed saccades has been shown. Using eye data from three previously published studies, we investigated how saccade rate changed while monkeys were presented with visual stimuli under conditions with loose or no viewing demands. In two conditions, animals passively sat while an LED lamp flashed or screen-wide images appeared in front of them. In the third condition, images were repeated semiperiodically while animals had to maintain their gaze within a wide rectangular area and detect oddballs. Despite animals not being required to maintain fixation or make saccades to particular targets, the onset of visual events led to a temporary reduction of saccade rate across all conditions. Interestingly, saccadic inhibition was found at image offsets as well. These results show that saccadic inhibition occurs in monkeys during free viewing. We investigated the time courses of saccade rate following visual stimuli during three conditions of free viewing in macaque monkeys. Under all conditions, saccade rate decreased transiently after the onset of visual stimuli. These results suggest that saccadic inhibition occurs during free viewing.
Topics: Humans; Animals; Saccades; Fixation, Ocular; Eye Movements; Macaca mulatta
PubMed: 36629324
DOI: 10.1152/jn.00225.2022 -
Schizophrenia Research Oct 2019Abnormal eye gaze is common in schizophrenia and linked to functional impairment. The hypothalamic neuropeptide oxytocin modulates visual attention to social stimuli,... (Randomized Controlled Trial)
Randomized Controlled Trial
Abnormal eye gaze is common in schizophrenia and linked to functional impairment. The hypothalamic neuropeptide oxytocin modulates visual attention to social stimuli, but its effects on eye gaze in schizophrenia are unknown. We examined visual scanning of faces in men with schizophrenia and neurotypical controls to quantify oxytocin effects on eye gaze. In a randomized, double-blind, crossover study, 33 men with schizophrenia and 39 matched controls received one dose of intranasal oxytocin (40 IU) and placebo on separate testing days. Participants viewed 20 color photographs of faces while their gaze patterns were recorded. We tested for differences in fixation time on the eyes between patients and controls as well as oxytocin effects using linear mixed-effects models. We also tested whether attachment style, symptom severity, and anti-dopaminergic medication dosage moderated oxytocin effects. In the placebo condition, patients showed reduced fixation time on the eyes compared to controls. Oxytocin was associated with an increase in fixation time among patients, but a decrease among controls. Higher attachment anxiety and greater symptom severity predicted increased fixation time on the eyes on oxytocin versus placebo. Anti-dopaminergic medication dosage and attachment avoidance did not impact response to oxytocin. Consistent with findings that oxytocin optimizes processing of social stimuli, intranasal oxytocin enhanced eye gaze in men with schizophrenia. Further work is needed to determine whether changes in eye gaze impact social cognition and functional outcomes. Both attachment anxiety and symptom severity predicted oxytocin response, highlighting the importance of examining potential moderators of oxytocin effects in future studies.
Topics: Adult; Double-Blind Method; Eye Movement Measurements; Facial Recognition; Fixation, Ocular; Humans; Male; Middle Aged; Object Attachment; Oxytocin; Schizophrenia; Social Perception; Time Factors
PubMed: 31416746
DOI: 10.1016/j.schres.2019.07.039 -
Vision Research Nov 2020When remembering an object at a given location, participants tend to return their gaze to that location even after the object has disappeared, known as...
When remembering an object at a given location, participants tend to return their gaze to that location even after the object has disappeared, known as Looking-at-Nothing (LAN). However, it is unclear whether LAN is associated with better memory performance. Previous studies reporting beneficial effects of LAN have often not systematically manipulated or assessed eye movements. We asked 20 participants to remember the location and identity of eight objects arranged in a circle, shown for 5 s. Participants were prompted to judge whether a location statement (e.g., "Star Right") was correct or incorrect, or referred to a previously unseen object. During memory retrieval, participants either fixated in the screen center or were free to move their eyes. Results reveal no difference in memory accuracy and response time between free-viewing and fixation while a LAN effect was found for saccades during free viewing, but not for microsaccades during fixation. Memory performance was better in those free-viewing trials in which participants made a saccade to the critical location, and scaled with saccade accuracy. These results indicate that saccade kinematics might be related to both memory performance and memory retrieval processes, but the strength of their link would differ between individuals and task demands.
Topics: Eye Movements; Fixation, Ocular; Humans; Memory; Mental Recall; Saccades
PubMed: 32827879
DOI: 10.1016/j.visres.2020.07.013 -
Scientific Reports Oct 2023Microsaccades, incessant "fixational eye movements" (< 1°), are an important window into cognitive functions. Yet, its role in visual perceptual learning...
Microsaccades, incessant "fixational eye movements" (< 1°), are an important window into cognitive functions. Yet, its role in visual perceptual learning (VPL)-improvements in visual discrimination due to practice-remains practically unexplored. Here we investigated whether and how microsaccades change in VPL. Human observers performed a Landolt acuity task for 5 consecutive days and were assigned to the Neutral or Attention group. On each trial, two peripheral Landolt squares were presented briefly along a diagonal. Observers reported the gap side of the target stimulus. Training improved acuity and modified the microsaccade rate; with training, the rate decreased during the fixation period but increased during the response cue. Furthermore, microsaccade direction during the response cue was biased toward the target location, and training enhanced and sped up this bias. Finally, the microsaccade rate during a task-free fixation period correlated with observers' initial acuity threshold, indicating that the fewer the microsaccades during fixation the better the individual visual acuity. All these results, which were similar for both the Neutral and Attention groups and at both trained and untrained locations, suggest that microsaccades could serve as a physiological marker reflecting functional dynamics in human perceptual learning.
Topics: Humans; Fixation, Ocular; Saccades; Cues; Visual Perception; Spatial Learning; Photic Stimulation
PubMed: 37783775
DOI: 10.1038/s41598-023-42768-w -
Journal of Vision May 2024What is the link between eye movements and sensory learning? Although some theories have argued for an automatic interaction between what we know and where we look that...
What is the link between eye movements and sensory learning? Although some theories have argued for an automatic interaction between what we know and where we look that continuously modulates human information gathering behavior during both implicit and explicit learning, there exists limited experimental evidence supporting such an ongoing interplay. To address this issue, we used a visual statistical learning paradigm combined with a gaze-contingent stimulus presentation and manipulated the explicitness of the task to explore how learning and eye movements interact. During both implicit exploration and explicit visual learning of unknown composite visual scenes, spatial eye movement patterns systematically and gradually changed in accordance with the underlying statistical structure of the scenes. Moreover, the degree of change was directly correlated with the amount and type of knowledge the observers acquired. This suggests that eye movements are potential indicators of active learning, a process where long-term knowledge, current visual stimuli and an inherent tendency to reduce uncertainty about the visual environment jointly determine where we look.
Topics: Humans; Eye Movements; Learning; Male; Young Adult; Female; Adult; Photic Stimulation; Visual Perception; Fixation, Ocular
PubMed: 38819805
DOI: 10.1167/jov.24.5.17 -
Vision Research Feb 2022Previous work suggests that subordinate-level object training improves exemplar-level perceptual discrimination over basic-level training. However, the extent to which...
Previous work suggests that subordinate-level object training improves exemplar-level perceptual discrimination over basic-level training. However, the extent to which visual fixation strategies and the use of visual features, such as color and spatial frequency (SF), change with improved discrimination was not previously known. In the current study, adults (n = 24) completed 6 days of training with 2 families of computer-generated novel objects. Participants were trained to identify one object family at the subordinate level and the other object family at the basic level. Before and after training, discrimination accuracy and visual fixations were measured for trained and untrained exemplars. To examine the impact of training on visual feature use, image color and SF were manipulated and tested before and after training. Discrimination accuracy increased for the object family trained at the subordinate-level, but not for the family trained at the basic level. This increase was seen for all image manipulations (color, SF) and generalized to untrained exemplars within the trained family. Both subordinate- and basic-level training increased average fixation duration and saccadic amplitude and decreased the number of total fixations. Collectively, these results suggest a dissociation between discrimination accuracy, indicative of recognition, and the associated pattern of changes present for visual fixations.
Topics: Adult; Fixation, Ocular; Humans; Pattern Recognition, Visual; Recognition, Psychology; Saccades
PubMed: 34826750
DOI: 10.1016/j.visres.2021.107971 -
Journal of Neurophysiology Aug 2020Express saccades are unusually short latency, visually guided saccadic eye movements. They are most commonly observed when the fixation spot disappears at a consistent,...
Express saccades are unusually short latency, visually guided saccadic eye movements. They are most commonly observed when the fixation spot disappears at a consistent, short interval before a target spot appears at a repeated location. The saccade countermanding task includes no fixation-target gap, variable target presentation times, and the requirement to withhold saccades on some trials. These testing conditions should discourage production of express saccades. However, two macaque monkeys performing the saccade countermanding task produced consistent, multimodal distributions of saccadic latencies. These distributions consisted of a longer mode extending from 200 ms to as much as 600 ms after target presentation and another consistently less than 100 ms after target presentation. Simulations revealed that, by varying express saccade production, monkeys could earn more reward. If express saccades were not rewarded, they were rarely produced. The distinct mechanisms producing express and longer saccade latencies were revealed further by the influence of regularities in the duration of the fixation interval preceding target presentation on saccade latency. Temporal expectancy systematically affected the latencies of regular but not of express saccades. This study highlights that cognitive control can integrate information across trials and strategically elicit intermittent very short latency saccades to acquire more reward. A serendipitous discovery that macaque monkeys produce express saccades under conditions that should discourage them reveals how cognitive control can adapt behavior to maximize reward.
Topics: Animals; Anticipation, Psychological; Behavior, Animal; Executive Function; Female; Fixation, Ocular; Macaca mulatta; Macaca radiata; Male; Reward; Saccades; Time Factors; Visual Perception
PubMed: 32667242
DOI: 10.1152/jn.00365.2020 -
Journal of Vision Apr 2020Fixation durations provide insights into processing demands. We investigated factors controlling fixation durations during scene viewing in two experiments. In...
Fixation durations provide insights into processing demands. We investigated factors controlling fixation durations during scene viewing in two experiments. In Experiment 1, we tested the degree to which fixation durations adapt to global scene processing difficulty by manipulating the contrast (from original contrast to isoluminant) and saturation (original vs. grayscale) of the entire scene. We observed longer fixation durations for lower levels of contrast, and longer fixation durations for grayscale than for color scenes. Thus fixation durations were globally slowed as visual information became more and more degraded, making scene processing increasingly more difficult. In Experiment 2, we investigated two possible sources for this slow-down. We used "checkerboard" stimuli in which unmodified patches alternated with patches from which luminance information had been removed (isoluminant patches). Fixation durations showed an inverted immediacy effect (longer, rather than shorter, fixation durations on unmodified patches) along with a parafoveal-on-foveal effect (shorter fixation durations, when an unmodified patch was fixated next). This effect was stronger when the currently fixated patch was isoluminant as opposed to unmodified. Our results suggest that peripheral scene information substantially affects fixation durations and are consistent with the notion of competition among the current and potential future fixation locations.
Topics: Adult; Female; Fixation, Ocular; Humans; Male; Time Factors; Visual Perception; Young Adult
PubMed: 32330229
DOI: 10.1167/jov.20.4.15 -
Nature Communications Sep 2021In spite of the reduced visual acuity, parafoveal information plays an important role in natural reading. However, competing models on reading disagree on whether words...
In spite of the reduced visual acuity, parafoveal information plays an important role in natural reading. However, competing models on reading disagree on whether words are previewed parafoveally at the lexical level. We find neural evidence for lexical parafoveal processing by combining a rapid invisible frequency tagging (RIFT) approach with magnetoencephalography (MEG) and eye-tracking. In a silent reading task, target words are tagged (flickered) subliminally at 60 Hz. The tagging responses measured when fixating on the pre-target word reflect parafoveal processing of the target word. We observe stronger tagging responses during pre-target fixations when followed by low compared with high lexical frequency targets. Moreover, this lexical parafoveal processing is associated with individual reading speed. Our findings suggest that reading unfolds in the fovea and parafovea simultaneously to support fluent reading.
Topics: Eye Movements; Female; Fixation, Ocular; Fovea Centralis; Humans; Macula Lutea; Male; Models, Neurological; Reading; Visual Cortex; Visual Perception; Young Adult
PubMed: 34475391
DOI: 10.1038/s41467-021-25571-x