Journal of Vision最新文献

After the offset of complex visual stimuli, rich stimulus information remains briefly available to the observer, reflecting a rapidly decaying iconic memory trace. Here we found that even if the cues are presented in the final stage of the stimulus presentation, the reportable information already starts decaying. Using closely spaced readout cues and a theoretical model of information availability, we observed that a cue has to be presented around 10 to 30 milliseconds before stimulus offset to access the full sensory information. We suggest that this does not reflect an early loss in sensory encoding, but instead it is a consequence of a latency in the processing of the cue that postpones the readout of the sensory representation by 10 to 30 milliseconds. Our analysis also shows that spatial proximity of items in complex arrays impacts sensory representation during both perceptual encoding and initial memory decay. Overall, these results provide a theoretical and empirical characterization of the readout from visual representations and offer a detailed insight into the transition from perception into iconic memory.

To describe the visual field of three common model species in vision science to understand the organization of their visual perceptual experience and contribute to continued studies of visual processing. Visual fields were measured using an ophthalmoscopic reflex technique in four common ferrets, four albino rats, and six northern tree shrews. Animals were anesthetized to avoid stress and the midpoint between their eyes was centered inside a spherical space. A rotating perimetric arm was manipulated in 10° increments around the head. At each increment, direct ophthalmoscopy was used to visualize limits of the retinal reflex for each eye, the overlap being the binocular visual field. Mean binocularity in the horizontal plane was 63.7 ± 5.1°, 79.1 ± 7.4°, and 53.6 ± 12.0° in the ferret, rat, and shrew, respectively. Maximum mean binocularity was 69.0 ± 1.6° in the ferret, 90.0 ± 3.1° in the rat, and 53.6 ± 12.2° in the shrew, located at 10° above, 40° above, and at the horizontal plane, respectively. Binocularity extended to 160°, 200°, and 180° in the sagittal plane in the ferret, rat, and shrew, respectively, from at least below the nose to above the head in all animals. Establishing the extent of the visual field accessible to the retina provides insight into the egocentric perceptual experience of animals. In describing the visual field, we provide a reference for the representation of the visual space in different cortical and retinal regions, many of which represent specific subregions of the visual field.

Gaze behavior during locomotion must balance the sampling of relevant information and the need for a stable gait. To maintain a safe gait in the light of declining resources, older adults might shift this balance toward the uptake of gait-related information. We investigated how violations of expectations affect gaze behavior and information uptake across age groups by asking younger and older adults to locomote through a virtual hallway, where they encountered expected and unexpected objects. We found that older adults look more on the floor, despite the translational locomotion, though not the rotational, being virtual. Dwell times on unexpected objects were increased in both age groups compared to expected objects. Although older adults showed shorter dwell times on expected objects, dwell times on unexpected objects were similar across age groups. Thus the difference between expected and unexpected objects was greater in older adults. Gaze distributions were more influenced by cognitive control capacities than by motor control capacities. Our findings indicate that unexpected information attracts attention during locomotion-particularly in older adults. However, during actual locomotion in the real world, increased information processing might come at the cost of reduced gait safety if processing resources are shifted away from stabilizing gait.

The accurate inference of causality between actions and their sensory outcomes requires determining their temporal relationship correctly despite variable delays within and across sensory modalities. Temporal recalibration-the perceptual realignment of actions with delayed sensory feedback-has been demonstrated across various sensorimotor domains. Here, we investigate whether this mechanism extends to saccadic eye movements and sensory events contingent on them. In three experiments, participants made horizontal saccades that triggered high-contrast flashes at varying delays. They then reported whether the flashes occurred during or after the saccade, allowing us to track perceived event timing. Exposure to consistent delays between saccade onset and the flash led to a shift in perceptual reports: flashes presented after saccade offset were more often judged as occurring during the movement. This recalibration effect was robust even when we manipulated relevant visual cues such as the presence of a structured background or the continuity of the saccade target. In a replay condition, we found a significant but much smaller recalibration effect between replayed saccades and flash, demonstrating the importance of action execution for visuomotor temporal recalibration. These findings highlight the visual system's remarkable adaptability to temporal delays between eye movements and their sensory consequences. A similar recalibration mechanism may support perceptual stability in natural vision by dynamically realigning saccades with their resulting visual input, even amid changing visual conditions.

When a manual reaching target is selected from a number of alternatives, decision uncertainty can often result in curvature of movement trajectories toward a nonchosen alternative. This curvature in the two-dimensional object plane is typically attributed to competitive interactions between different movement goals. Several models of action selection assume an explicit link between the momentary position of the hand and the state of the underlying decision process. Under this assumption, tracking the position of the hand can be used to infer the temporal evolution of the decision. However, even without a selection requirement, movements show variable amounts of curvature due to motor noise. We assessed the relative contributions of decision uncertainty and motor noise to the variability in curvature in naturalistic reach-to-grasp actions. Participants had to pick up one of two blocks (the brighter/dimmer block) and we manipulated decision uncertainty by varying the luminance difference between the two blocks. Single target baseline reaches were included to model the variability in curvature without a choice requirement. We assessed to what extent this baseline model can account for the curvature distributions observed under choice conditions, and tested several modifications of the model to capture any effects of decision uncertainty. The best model of the curvature distributions under choice conditions involved a mixture of the baseline component along with a separate choice component. The weight of this choice component and analysis of the likelihood of observed reaches under the choice/baseline components, suggest that the majority of reaches were unaffected by decision uncertainty and were compatible with the natural variability in movement trajectories due to motor noise. Unless the variability induced by factors unrelated to the decision process is adequately accounted for, the role of decision uncertainty may be overstated when it is inferred from reach trajectories.

A fundamental challenge in motion perception lies in the fact that the global motion of any translating object will generate a heterogeneous set of local motion signals that vary depending on the oriented contour information within each local region. This so-called aperture problem illustrates how the visual system must integrate diverse types of motion signals to attain direction selectivity that is invariant to visual form. Here, we investigated how form-invariant motion selectivity emerges across the human visual pathway by using functional magnetic resonance imaging (fMRI) to measure direction-selective responses to drifting gratings and random-dot motion, and then testing for reliable generalization across stimulus types. All visual areas of interest showed highly reliable direction-selective classification performance for a given stimulus type, but early areas V1 and V2 showed chance-level generalization between motion types. Indeed, V1 responses tended to confuse random-dot motion as resembling orthogonal grating motion, implying that drifting random dots generated oriented motion-streak responses in V1. By contrast, motion-sensitive areas MT+ and V3A showed reliable cross-generalization performance in our fMRI experiments that tested both linear and spiral motion trajectories. Our findings provide compelling evidence that motion direction selectivity becomes more invariant to stimulus form in higher visual areas, particularly along the dorsal visual pathway.

During self-movement, the visual system can identify scene-relative object motion via flow parsing and estimate the direction of self-movement (heading) from optic flow. However, the temporal dynamics of these two processes have not been examined and compared using matched displays. In this study, we examined how the accuracy of flow parsing and heading estimation changed with stimulus duration. Participants viewed a stereo optic flow display simulating forward translational self-movement through a cloud composed of wireframe objects with stimulus durations at 100, 200, 400, 700, and 1000 ms. In Experiment 1, a yellow dot probe moved vertically for 100 ms in the scene near the end of the trial. A nulling motion component was added through an adaptive staircase to the probe's image motion to determine when the probe was perceived to move vertically in the scene, which was then used to compute the accuracy of flow parsing. In Experiment 2, participants viewed the same optic flow display without the moving probe object. The simulated heading was randomly varied in each trial, and participants were asked to estimate heading at the end of the trial. As stimulus duration increased, the accuracy of flow parsing decreased, whereas the accuracy of heading estimation increased. These contrasting temporal dynamics suggest that despite both processes relying on optic flow, flow parsing and heading estimation involve distinct processing mechanisms with different temporal characteristics. This divergence, together with previous neurophysiological findings, led us to propose two potential neural mechanisms subserving these two processes to inspire future research.

Locomotion poses a challenge to clear and stable vision. Reflexive head and eye movements act to stabilize the retinal image, but these do not act perfectly, so retinal image motion is increased during walking compared with standing. We nevertheless perceive the world as clear and stable during locomotion, suggesting that the visual system is well-adapted to meet the challenges posed by locomotion. To better understand these processes, we assessed dynamic contrast sensitivity during locomotion by presenting brief (24 ms) foveal Gabor targets (6°, 11 cpd) at threshold contrast to observers walking on a treadmill in an otherwise darkened room. Head and ankle motion were tracked, and presentation time was randomized, which allowed post hoc binning of responses according to stride-cycle timing to investigate how sensitivity is impacted by head motion and stride-cycle timing. Contrast sensitivity was improved during walking compared with standing over large portions of the stride cycle, except for epochs aligned with heel strikes, which drive large and unpredictable perturbations. This resulted in periodicity in contrast sensitivity at two cycles per stride, with additional oscillations observed at four and six cycles per stride. Pupil size was found to be moderately larger during walking compared with standing and also exhibited periodic fluctuations that were phase-locked to the stride cycle. Perceptual oscillations reflect the entrainment of visual processing by active behaviors. Robust contrast sensitivity during walking may be supported by action-contingent effects of locomotion on visual cortical activity that have been observed in several animal models.

What is the impact of dynamic changes in facial visibility on identifying the eye and forehead region? This study examines how wearing or removing a mask affects the ability to visually identify the eyes. We investigate whether these changes impact the recognition of upper facial features and alter sensitivity to the misalignment of the face's upper and lower halves, which disrupts holistic face processing. Results show that removing a mask generally impairs visual identification, suggesting that the perception of the whole face hinders recognition of the upper half. This hindering is evident from the fact that the interference decreases when the face is misaligned. In contrast, the impairment in identification caused by adding a mask to a target face rises from losing original support of the holistic processing, given that it was not diminished when the upper and bottom halves were misaligned. Additional findings show that misalignment negatively affects the identification of faces where a mask was either maintained or added, suggesting that masks may actually help direct attention to relevant facial features, rather than being integrated into a holistic representation. We discuss these results in light of their theoretical and practical implications for visual identification, particularly in the context of dynamic changes to facial appearance.

During visual search, our attention extends around each fixation. It has been suggested that, in aging, there is a reduced attentional field, leading to visual function declines. To investigate the attentional field, 30 younger and 20 older adults performed a pop-out visual search task. We estimated each participant's attentional field size based on their search times in the presence of different sizes of gaze-contingent visible windows (25°, 20°, and 15° around fixation). Further, we tested whether performance in the visual search task was related to peripheral visual function. Participants performed a contrast discrimination task and two motion perception tasks (local and global motion perception). In these tasks, stimuli were presented at two different peripheral eccentricities (5° and 10°). Overall, older adults took longer than younger adults to report the presence of the target in the control full-view pop-out search task. Compared to younger participants, they also had a significantly smaller attentional field. In addition, irrespective of eccentricity, older adults had higher peripheral contrast discrimination thresholds and a higher threshold in global motion perception, but not local. We also found negative correlations between attentional field size and thresholds for contrast discrimination and for global motion perception for older adults. In conclusion, we observed reduced attentional fields in aging, which were associated with lowered contrast and lowered global motion perception. These results highlight the importance of spatial covert attention in peripheral visual function and support the notion of a decline in the functions of the dorsal visual network in aging.