Journal of Vision最新文献

This study examines the temporal and spatial components of microsaccade dynamics in homonymous hemianopia (HH) after ischemic stroke, and their association with patients' visual impairments. The eye position data were recorded during visual field testing in 15 patients with HH and 15 controls. Microsaccade rate (temporal) and direction (spatial) dynamics in HH were analyzed across visual field sectors with varying defect depth and compared with controls. Support vector machines were trained to characterize the visual field defects in HH based on microsaccade dynamics. Patients exhibited stronger microsaccadic inhibition in the sighted areas, postponed and stronger microsaccadic inhibition in areas of residual vision (ARVs) compared to controls. Meanwhile, a rebound was evident in the sighted areas but absent in the ARVs and blind areas. Microsaccades surviving the inhibition were more attracted toward the stimulus, whereas microsaccades after the inhibition were directed away from the stimulus in controls. Such pattern was not observed in HH. Dissociated temporal and spatial impairments of microsaccade dynamics suggest multi-fold impairments of the visual and oculomotor networks in HH. Based on the microsaccadic phase signature underlying microsaccade rate dynamics, we characterized patients' visual field defects and discovered regions with residual function inside both the blind and sighted hemifields. These findings suggest that monitoring microsaccade dynamics may provide valuable supplementary information beyond that captured by behavioral responses.

This study investigates how optical information and dynamical constraints influence movement production and perception. In Experiment 1, 16 volunteers walked or performed a Y-balance movement with and without sight on sturdy or foam-padded floors. The optical information and force environment affected the participants' kinematics, such as stride duration, stride length, stride width, gait speed, joint ranges of motion for walking, total movement duration, and joint ranges of motion for Y-balance. Naïve observers then watched these movements on a point-light display and distinguished movements executed under different optical information (Experiment 2) and force environment (Experiment 3) conditions. They were able to pick out movements performed without sight, especially for those performed on a padded floor; they were also able to discriminate movements performed on different supporting surfaces, especially when the actors were blindfolded. Thus, discriminating movement conditions from point-light displays was possible, and better with higher kinematic variability. Logistic regressions showed discriminating movements relied on the movement kinematics that varied the most between conditions. This information was valid and useful regardless of viewing perspective; that is, whether the walking and Y-balance were displayed in the frontal or side view, the perceptual performance was equivalent. Thus, both optical information and dynamical constraints shape movement patterns in ways that are perceptible through the kinematic variations.

Studies of the early visual system often require characterizing the visual preferences of large populations of neurons. This task typically requires multiple stimuli such as sparse noise and drifting gratings, each of which probes only a limited set of visual features. Here, we introduce a new dynamic stimulus with sharp-edged stripes that we term Zebra noise and a new analysis model based on wavelets, and we show that in combination they are highly efficient for mapping multiple aspects of the visual preferences of thousands of neurons. We used two-photon calcium imaging to record the activity of neurons in the mouse visual cortex. Zebra noise elicited strong responses that were more repeatable than those evoked by traditional stimuli. The wavelet-based model captured the repeatable aspects of the resulting responses, providing measures of neuronal tuning for multiple stimulus features: position, orientation, size, spatial frequency, drift rate, and direction. The method proved efficient, requiring only 5 minutes of stimulus (repeated three times) to characterize the tuning of thousands of neurons across visual areas. In combination, the Zebra noise stimulus and the wavelet-based model provide a broadly applicable toolkit for the rapid characterization of visual representations, promising to accelerate future studies of visual function.

To correctly parse the visual scene, one must detect edges and determine their underlying cause. Previous work has demonstrated that neural networks trained to differentiate shadow and occlusion edges exhibit sensitivity to boundary sharpness and texture differences. Here, we investigate whether human observers are also sensitive to these cues using synthetic edge stimuli formed by quilting together two natural textures, allowing us to parametrically manipulate boundary sharpness, texture modulation, and luminance modulation. Observers classified five sets of synthetic boundary images as shadows, occlusions, or textures generated by varying these three cues in all possible combinations. These three cues exhibited strong interactions to determine categorization. For sharp edges, increasing luminance modulation made it less likely the patch would be classified as a texture and more likely it would be classified as an occlusion, whereas for blurred edges, increasing luminance modulation made it more likely the patch would be classified as a shadow. Boundary sharpness had a profound effect, so that in the presence of luminance modulation, increasing sharpness decreased the likelihood of classification as a shadow and increased the likelihood of classification as an occlusion. Texture modulation had little effect, except for a sharp boundary with zero luminance modulation. Results were consistent across all five stimulus sets, and human performance was well explained by a multinomial logistic regression model. Our results demonstrate that human observers make use of the same cues as previous machine learning models when detecting and determining the cause of an edge.

For goal-directed movements like throwing darts or shooting a soccer penalty, the optimal location to aim depends on the endpoint variability of an individual. Currently, there is no consensus on whether people can optimize their movement planning based on information about their motor variability. Here, we tested the role of different types of feedback for movement planning under risk. We measured saccades toward a bar that consisted of a reward and a penalty region. Participants either received error-based feedback about their endpoint or reinforcement feedback about the resulting reward. We additionally manipulated the feedback schedule to assess the role of feedback frequency and whether feedback focusses on individual trials or a group of trials. Participants with trial-by-trial reinforcement feedback performed best. They were less loss-aversive, had the least endpoint deviation from optimality, and showed more consistent performance at the group level. This combination of reduced between-participant variability and the improved alignment with optimality suggests that reinforcement feedback about a single movement is particularly effective to optimize movement planning under risk.

Visual rivalry paradigms provide a powerful tool for probing the mechanisms of visual awareness and perceptual suppression. Although the dynamics and determinants of perceptual switches in visual rivalry have been extensively studied and modeled, recent advances in experimental design-particularly those that quantify the depth and variability of perceptual suppression-have outpaced the development of computational models. Here we extend an existing dynamical model of binocular rivalry to encompass two novel experimental paradigms: a threshold detection variant of binocular rivalry, and tracking continuous flash suppression. Together, these tasks provide complementary measures of the dynamics and magnitude of perceptual suppression. Through numerical simulation, we demonstrate that a single mechanism, competitive (hysteretic) inhibition between slowly adapting monocular populations, is sufficient to account for the suppression depth findings across both paradigms. This unified model offers a foundation for the development of a quantitative theory of perceptual suppression in visual rivalry.

Individuals with cerebral visual impairment (CVI) often struggle with visuospatial processing, particularly in highly cluttered or complex environments. These challenges are commonly assessed through visual search tasks, using global measures such as reaction time (RT), accuracy, and search area. Accordingly, impaired search performance in CVI manifests as longer RTs, lower accuracy, and broader search areas. However, rather than elucidating the underlying mechanism of the impaired search process, these measures decode its outcome. In the present study, we utilized eye-tracking data to compute detailed measures of fixation count and duration, aiming to characterize gaze pattern sequences and determine whether prolonged RTs in CVI stem from slower visual scanning or increased fixation counts. Our reanalysis of two previously published datasets reveals that longer RTs in CVI arise from elevated fixation counts, specifically on distractors, rather than from slower visual scanning. Our findings indicate recurrent disruptions in maintaining gaze on the target, likely reflecting difficulties in sustaining attention on the target, suppressing distractors, and preventing inhibition of return. Together, these findings highlight an inefficient search pattern that is more biased toward distractors than focused on targets. By revealing these underlying mechanisms, gaze-based measures offer a deeper understanding of visuospatial processing deficits in CVI.

In macular degeneration (MD), depth perception from binocular disparity is impacted in regions with vision loss in either eye, but monocular cues like motion parallax remain available. This study investigates whether combining motion parallax with disparity improves depth perception and compensates for the loss of depth due to central field loss (CFL). Eleven MD participants and 19 controls viewed a horizontal sine-wave corrugation in depth, defined by disparity and/or motion parallax, judging which half-cycle appeared farther away in depth. We measured thresholds for each cue alone and for the two cues combined. In MD participants, cue integration benefits depended on scotoma characteristics. Disparity performance correlated strongly with the size of the stereoblind zone, while motion parallax thresholds showed no significant relation, suggesting preservation despite CFL. MD participants with extensive stereoblind zones showed elevated thresholds for both single cues compared to controls but demonstrated optimal integration when disparity was added to motion parallax. Those with small stereoblind zones achieved control-like thresholds and exhibited optimal or better than predicted integration. However, asymmetric patterns emerged with suboptimal performance when motion parallax was added to threshold disparity. Controls with simulated scotomas maintained stable integration, contrasting with variable patterns in MD. Our results show that individuals with CFL retain significant capacity for depth cue integration, contingent upon residual binocular disparity. Thus, motion parallax emerges as a valuable compensatory cue to improve depth perception in individuals with MD.

How stimulus properties are processed in the human brain over time is critical to how we engage in dynamic everyday environments. To understand how changes in basic stimulus properties relate to changes in human electrical brain activity over time, previous work has estimated the brain's temporal response function (TRF) by cross-correlating random luminance sequences with electroencephalogram (EEG) signals at various lags to approximate the brain's response to temporal changes in luminance. Using this technique, it was found that luminance changes produce long-lasting "echoes" in the alpha frequency range. However, the neural origin of these echoes and the precise stimulus features that induce them have not been extensively studied. We measured TRFs in response to luminance and contrast changes. Additionally, the fact that EEG responses generated in the primary visual cortex (V1) have a unique pattern of polarity reversal depending on the visual field location (with upper stimuli projecting negatively and lower projecting positively) allowed us to test whether the TRFs generated from upper or lower visual field stimulation were counter-phased, as would be expected if the echoes were generated within V1. We found a luminance echo lasting ∼1 s in the alpha frequency and contrast echoes lasting only around 300 ms. For both stimuli, the TRF was initially counter-phased between upper and lower visual fields but quickly became in phase after ∼100 ms. Our findings demonstrate the existence of contrast (in addition to luminance) echoes in the alpha band, which appear to emerge from V1, perhaps as a traveling wave.

Continuous flash suppression (CFS) is a variant of interocular conflict that occurs when one eye views a dynamic high-contrast mask that increases the duration of target suppression. A variant of CFS known as tracking continuous flash suppression (tCFS) was developed, allowing the depth of interocular suppression to be measured. Although previous research has measured how the duration of suppression may be modulated by the contrast and size of the masking stimulus, no study has assessed how mask features impact suppression depth. In our first study, we manipulated mask contrast to measure the consequent impact on suppression depth as measured by the tCFS procedure. We observed that high mask contrast increased the threshold required for a target to break into awareness. Critically, the decrease in contrast required to re-suppress each target was proportionately the same across all conditions so that suppression depth-the ratio of the two thresholds-remained constant. In the second experiment, we manipulated the size of the masking stimulus and found no change in breakthrough/suppression thresholds or suppression depth (i.e., the difference between the thresholds when using log-contrast). These findings clarify that, although changes in mask contrast may alter the threshold to enter awareness, there is no overall change in suppression depth as the changes in breakthrough threshold are reflected by proportionately equivalent changes in suppression threshold. This result matches findings obtained with binocular rivalry showing that suppression depth is constant despite changes in stimulus contrast. Differing levels of mask contrast and size, therefore, can be used by researchers in CFS without altering the strength of suppression, consistent with the perspective that interocular suppression operates in small local spatial zones determined by receptive field size in the primary visual cortex.