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Current Biology : CB Feb 2022Humans are remarkably proficient at finding objects within complex visual scenes. According to current theories of attention, visual processing of an object of interest...
Humans are remarkably proficient at finding objects within complex visual scenes. According to current theories of attention, visual processing of an object of interest is favored through the preparatory activation of object-specific representations in visual cortex. One key problem that is inherent to real-world visual search but is not accounted for by current theories is that a given object will produce a dramatically different retinal image depending on its location, which is unknown in advance. For instance, the color of the retinal image depends on the illumination on the object, its shape depends on the viewpoint, and (most critically) its size can vary by several orders of magnitude, depending on the distance to the observer. In order to benefit search, preparatory activity thus needs to incorporate contextual expectations. In the current study, we measured fMRI blood-oxygen-level-dependent (BOLD) activity in human observers while they prepared to search for objects at different distances in indoor-scene photographs. First, we established that observers instantiated preparatory object representations: activity patterns in object-selective cortex evoked during search preparation (while no objects were presented) resembled activity patterns evoked by viewing those objects in isolation. Second, we demonstrated that these preparatory object representations were systematically modulated by expectations derived from scene context: activity patterns reflected the predicted retinal image of the object at each distance (i.e., distant search evoking smaller object representations and nearby search evoking larger object representations). These findings reconcile current theories of attentional selection with the challenges of real-world vision.
Topics: Attention; Brain Mapping; Humans; Magnetic Resonance Imaging; Motivation; Pattern Recognition, Visual; Photic Stimulation; Visual Cortex; Visual Perception
PubMed: 34919809
DOI: 10.1016/j.cub.2021.11.062 -
Journal of Vision Apr 2024We obtain large amounts of external information through our eyes, a process often considered analogous to picture mapping onto a camera lens. However, our eyes are never...
We obtain large amounts of external information through our eyes, a process often considered analogous to picture mapping onto a camera lens. However, our eyes are never as still as a camera lens, with saccades occurring between fixations and microsaccades occurring within a fixation. Although saccades are agreed to be functional for information sampling in visual perception, it remains unknown if microsaccades have a similar function when eye movement is restricted. Here, we demonstrated that saccades and microsaccades share common spatiotemporal structures in viewing visual objects. Twenty-seven adults viewed faces and houses in free-viewing and fixation-controlled conditions. Both saccades and microsaccades showed distinctive spatiotemporal patterns between face and house viewing that could be discriminated by pattern classifications. The classifications based on saccades and microsaccades could also be mutually generalized. Importantly, individuals who showed more distinctive saccadic patterns between faces and houses also showed more distinctive microsaccadic patterns. Moreover, saccades and microsaccades showed a higher structure similarity for face viewing than house viewing and a common orienting preference for the eye region over the mouth region. These findings suggested a common oculomotor program that is used to optimize information sampling during visual object perception.
Topics: Humans; Saccades; Male; Female; Adult; Fixation, Ocular; Young Adult; Visual Perception; Photic Stimulation; Pattern Recognition, Visual
PubMed: 38656530
DOI: 10.1167/jov.24.4.20 -
Journal of Vision Feb 2022Continuous tracking is a newly developed technique that allows fast and efficient data acquisition by asking participants to "track" a stimulus varying in some property...
Continuous tracking is a newly developed technique that allows fast and efficient data acquisition by asking participants to "track" a stimulus varying in some property (usually position in space). Tracking is a promising paradigm for the investigation of dynamic features of perception and could be particularly well suited for testing ecologically relevant situations difficult to study with classical psychophysical paradigms. The high rate of data collection may be useful in studies on clinical populations and children, who are unable to undergo long testing sessions. In this study, we designed tracking experiments with two novel stimulus features, numerosity and size, proving the feasibility of the technique outside standard object tracking. We went on to develop an ideal observer model that characterizes the results in terms of efficiency of conversion of stimulus strength into responses, and identification of early and late noise sources. Our ideal observer closely modeled results from human participants, providing a generalized framework for the interpretation of tracking data. The proposed model allows to use the tracking paradigm in various perceptual domains, and to study the divergence of human participants from ideal behavior.
Topics: Child; Humans; Models, Psychological; Motion Perception; Perceptual Masking; Space Perception; Visual Perception
PubMed: 35103756
DOI: 10.1167/jov.22.2.3 -
BMC Biology Nov 2022Sequential effects of environmental stimuli are ubiquitous in most behavioral tasks involving magnitude estimation, memory, decision making, and emotion. The human...
BACKGROUND
Sequential effects of environmental stimuli are ubiquitous in most behavioral tasks involving magnitude estimation, memory, decision making, and emotion. The human visual system exploits continuity in the visual environment, which induces two contrasting perceptual phenomena shaping visual perception. Previous work reported that perceptual estimation of a stimulus may be influenced either by attractive serial dependencies or repulsive aftereffects, with a number of experimental variables suggested as factors determining the direction and magnitude of sequential effects. Recent studies have theorized that these two effects concurrently arise in perceptual processing, but empirical evidence that directly supports this hypothesis is lacking, and it remains unclear whether and how attractive and repulsive sequential effects interact in a trial. Here we show that the two effects concurrently modulate estimation behavior in a typical sequence of perceptual tasks.
RESULTS
We first demonstrate that observers' estimation error as a function of both the previous stimulus and response cannot be fully described by either attractive or repulsive bias but is instead well captured by a summation of repulsion from the previous stimulus and attraction toward the previous response. We then reveal that the repulsive bias is centered on the observer's sensory encoding of the previous stimulus, which is again repelled away from its own preceding trial, whereas the attractive bias is centered precisely on the previous response, which is the observer's best prediction about the incoming stimuli.
CONCLUSIONS
Our findings provide strong evidence that sensory encoding is shaped by dynamic tuning of the system to the past stimuli, inducing repulsive aftereffects, and followed by inference incorporating the prediction from the past estimation, leading to attractive serial dependence.
Topics: Humans; Decision Making; Visual Perception; Vision, Ocular
PubMed: 36345010
DOI: 10.1186/s12915-022-01444-7 -
International Journal of Environmental... Jun 2022Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether...
Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether microsaccadic activity is modulated by the speed of radial optic flow stimuli. Experiments were performed in the dark on 19 subjects who stood in front of a screen covering 135 × 107° of the visual field. Subjects were instructed to fixate on a central fixation point while optic flow stimuli were presented in full field, in the foveal, and in the peripheral visual field at different dot speeds (8, 11, 14, 17, and 20°/s). Fixation in the dark was used as a control stimulus. For almost all tested speeds, the stimulation of the peripheral retina evoked the highest microsaccade rate. We also found combined effects of optic flow speed and the stimulated retinal region (foveal, peripheral, and full field) for microsaccade latency. These results show that optic flow speed modulates microsaccadic activity when presented in specific retinal portions, suggesting that eye movement generation is strictly dependent on the stimulated retinal regions.
Topics: Fixation, Ocular; Humans; Optic Flow; Photic Stimulation; Retina; Saccades; Visual Perception
PubMed: 35682346
DOI: 10.3390/ijerph19116765 -
ELife Nov 2020Neurons in primate V4 exhibit various types of selectivity for contour shapes, including curves, angles, and simple shapes. How are these neurons organized in V4 remains...
Neurons in primate V4 exhibit various types of selectivity for contour shapes, including curves, angles, and simple shapes. How are these neurons organized in V4 remains unclear. Using intrinsic signal optical imaging and two-photon calcium imaging, we observed submillimeter functional domains in V4 that contained neurons preferring curved contours over rectilinear ones. These curvature domains had similar sizes and response amplitudes as orientation domains but tended to separate from these regions. Within the curvature domains, neurons that preferred circles or curve orientations clustered further into finer scale subdomains. Nevertheless, individual neurons also had a wide range of contour selectivity, and neighboring neurons exhibited a substantial diversity in shape tuning besides their common shape preferences. In strong contrast to V4, V1 and V2 did not have such contour-shape-related domains. These findings highlight the importance and complexity of curvature processing in visual object recognition and the key functional role of V4 in this process.
Topics: Animals; Brain Mapping; Form Perception; Macaca mulatta; Male; Nerve Net; Neurons; Pattern Recognition, Visual; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 33211007
DOI: 10.7554/eLife.57502 -
Philosophical Transactions of the Royal... Jan 2023The dominant inferential approach to human 3D perception assumes a model of spatial encoding based on a physical description of objects and space. Prevailing models... (Review)
Review
The dominant inferential approach to human 3D perception assumes a model of spatial encoding based on a physical description of objects and space. Prevailing models based on this physicalist approach assume that the visual system infers an objective, unitary and mostly veridical representation of the external world. However, careful consideration of the phenomenology of 3D perception challenges these assumptions. I review important aspects of phenomenology, psychophysics and neurophysiology which suggest that human visual perception of 3D objects and space is underwritten by distinct and dissociated spatial encodings that are optimized for specific regions of space. Specifically, I argue that 3D perception is underwritten by at least three distinct encodings for (1) egocentric distance perception at the ambulatory scale, (2) exocentric distance (scaled depth) perception optimized for near space, and (3) perception of object shape and layout (unscaled depth). This tripartite division can more satisfactorily account for the phenomenology, psychophysics and adaptive logic of human 3D perception. This article is part of a discussion meeting issue 'New approaches to 3D vision'.
Topics: Humans; Depth Perception; Psychophysics; Distance Perception; Visual Perception; Space Perception
PubMed: 36511412
DOI: 10.1098/rstb.2021.0454 -
Journal of Vision Feb 2021The visual system can predict visual features across saccades based on learned transsaccadic associations between peripheral and foveal input. This has been shown for...
The visual system can predict visual features across saccades based on learned transsaccadic associations between peripheral and foveal input. This has been shown for simple visual features such as shape, size, and spatial frequency. The present study investigated whether transsaccadic predictions are also made for more complex visual stimuli. In an acquisition phase, new transsaccadic associations were established. In the first experiment, pictures of real-world objects changed category during the saccade (fruits were changed into balls or vice versa). In the second experiment, the gender of faces was manipulated during the saccade (faces changed from male to female or vice versa). In the following test phase, the stimuli were briefly presented in the periphery, and participants had to indicate which object or face, respectively, they had perceived. In both experiments, peripheral perception was biased toward the acquired associated foveal input. These results demonstrate that transsaccadic predictions are not limited to a small set of simple visual features but can also be made for more complex and realistic stimuli. Multiple new associations can be learned within a short time frame, and the resulting predictions appear to be object specific.
Topics: Adult; Association Learning; Female; Humans; Male; Photic Stimulation; Saccades; Visual Perception; Young Adult
PubMed: 33620379
DOI: 10.1167/jov.21.2.10 -
Journal of Neurophysiology Apr 2022Expectations about forthcoming visual motion shaped by observers' experiences are known to induce anticipatory smooth eye movements (ASEMs) and changes in visual...
Expectations about forthcoming visual motion shaped by observers' experiences are known to induce anticipatory smooth eye movements (ASEMs) and changes in visual perception. Previous studies have demonstrated discrete effects of expectations on the control of ASEM and perception. However, the tasks designed in those studies were not able to segregate the effects of expectations and execution of ASEM itself on perception. In the present study, we attempted to directly examine the effect of ASEM itself on visual speed perception with a two-alternative forced-choice (2AFC) task, in which observers were asked to track a pair of sequentially presented visual motion stimuli with their eyes and to judge whether the second stimulus (test stimulus) was faster or slower than the first (reference stimulus). Our results showed that observers' visual speed perception, quantified by a psychometric function, shifted according to ASEM velocity. This was the case even though there was no difference in the steady-state eye velocity. Further analyses revealed that the observers' perceptual decisions could be explained by a difference in the magnitude of retinal slip velocity in the initial phase of ocular tracking when the reference and test stimuli were presented, rather than in the steady-state phase. Our results provide psychophysical evidence of the importance of initial ocular tracking in visual speed perception and the strong impact of ASEM. We provide psychophysical evidence that the execution of anticipatory smooth eye movement (ASEM) leads to underestimation of visual speed perception, that is, observers perceive the object motion velocity as slower than when ASEM is not induced, even though the performance of subsequent ocular tracking is comparable. Moreover, our results showed that such perceptual decisions regarding object motion velocity were derived from the ASEM-induced decrease in retinal slip velocity during the initial phase of ocular tracking.
Topics: Eye Movements; Motion Perception; Pursuit, Smooth; Visual Perception
PubMed: 35353633
DOI: 10.1152/jn.00498.2021 -
Clinical and Experimental Dental... Feb 2023It is well known that a good microsurgeon needs eight important factors: a high resolution view, an optimally magnified view, optimal brightness of the working field,...
OBJECTIVES
It is well known that a good microsurgeon needs eight important factors: a high resolution view, an optimally magnified view, optimal brightness of the working field, optimal working space, fine surgical instruments and devices, fine motor skills, precise hand-eye coordination, and fine visual perceptions. Of these factors, the first five are highly depending on manufacturer development abilities. The remaining factors have a lots of possibilities that microsurgeons can improve by themselves. A microsurgeon needs to identify shape, size, angle, inclination, length, height, depth, spatial position, centering in the optical field, orthogonality, and parallelism in a second. Knowing one's tendency and acuity in perceptions, learning perceptions that one is not good at, and paying selective attention on one's difficult perceptions, will provide better surgical outcome. Aim of this series of research is designing visual targets measuring specific visual perceptions for microsurgeons, achieving mean values of each perceptions, and identifying the tendency on each perceptions.
MATERIAL AND METHODS
Two hundred and eighty volunteer dentists in Japan and France were tested and multiple comparisons were made among age, gender, visual acuity, three magnification levels, and inclination angles against a standard target.
RESULTS AND COCLUSION
There is a tendency that identifying 1° misalignment in parallelism is difficult.
Topics: Humans; Japan; Learning; Visual Acuity; Visual Perception; Microsurgery; Surgeons
PubMed: 36349438
DOI: 10.1002/cre2.684