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Philosophical Transactions of the Royal... Jan 2023Decades of research have shown that absolute egocentric distance is underestimated in virtual environments (VEs) when compared with the real world. This finding has... (Review)
Review
Decades of research have shown that absolute egocentric distance is underestimated in virtual environments (VEs) when compared with the real world. This finding has implications on the use of VEs for applications that require an accurate sense of absolute scale. Fortunately, this underperception of scale can be attenuated by several factors, making perception more similar to (but still not the same as) that of the real world. Here, we examine these factors as two categories: (i) experience inherent to the observer, and (ii) characteristics inherent to the display technology. We analyse how these factors influence the sources of information for absolute distance perception with the goal of understanding how the scale of virtual spaces is calibrated. We identify six types of cues that change with these approaches, contributing both to a theoretical understanding of depth perception in VEs and a call for future research that can benefit from changing technologies. This article is part of the theme issue 'New approaches to 3D vision'.
Topics: Virtual Reality; Distance Perception; Cues; Vision, Ocular; Technology; User-Computer Interface
PubMed: 36511405
DOI: 10.1098/rstb.2021.0456 -
ENeuro 2022Stereoscopic vision enables the perception of depth. To study the brain mechanisms behind stereoscopic vision using noninvasive brain imaging (magnetic resonance brain...
Stereoscopic vision enables the perception of depth. To study the brain mechanisms behind stereoscopic vision using noninvasive brain imaging (magnetic resonance brain imaging; MRI), scientists need to reproduce the independent views of the left and right eyes in the brain scanner using "dichoptic" displays. However, high-quality dichoptic displays are technically challenging and costly to implement in the MRI scanner. The novel miniature stereoscope system ("MRI stereoscope") is an affordable and open-source tool that displays high-quality dichoptic images inside the MRI scanner. The MRI stereoscope takes advantage of commonly used display equipment, the MRI head coil, and a display screen. To validate the MRI stereoscope, binocular disparity stimuli were presented in a 3T MRI scanner while neural activation was recorded using functional MRI in six human participants. The comparison of large binocular disparities compared with disparities close to zero evoked strong responses across dorsal and ventral extra-striate visual cortex. In contrast, binocularly anti-correlated stimuli, which are not perceived in depth, did not evoke comparable activation. These results are the proof-of-concept that the MRI stereoscope can deliver dichoptic images that produce the perception of stereoscopic depth during acquisition of MR responses. Application of the MRI stereoscope to neuroscience can help to address important questions in perception and consciousness.
Topics: Humans; Magnetic Resonance Imaging; Neuroimaging; Photic Stimulation; Vision Disparity; Vision, Binocular
PubMed: 35045974
DOI: 10.1523/ENEURO.0382-21.2021 -
Journal of Vision Apr 2024The perceived slant of a stereoscopic surface is altered by the presence of a surrounding surface, a phenomenon termed stereo slant contrast. Previous studies have shown...
The perceived slant of a stereoscopic surface is altered by the presence of a surrounding surface, a phenomenon termed stereo slant contrast. Previous studies have shown that a slanted surround causes a fronto-parallel surface to appear slanted in the opposite direction, an instance of "bidirectional" contrast. A few studies have examined slant contrast using slanted as opposed to fronto-parallel test surfaces, and these also have shown slant contrast. Here, we use a matching method to examine slant contrast over a wide range of combinations of surround and test slants, one aim being to determine whether stereo slant contrast transfers across opposite directions of test and surround slant. We also examine the effect of the test on the perceived slant of the surround. Test slant contrast was found to be bidirectional in virtually all test-surround combinations and transferred across opposite test and surround slants, with little or no decline in magnitude as the test-surround slant difference approached the limit. There was a weak bidirectional effect of the test slant on the perceived slant of the surround. We consider how our results might be explained by four mechanisms: (a) normalization of stereo slant to vertical; (b) divisive normalization of stereo slant channels in a manner analogous to the tilt illusion; (c) interactions between center and surround disparity-gradient detectors; and (d) uncertainty in slant estimation. We conclude that the third of these (interactions between center and surround disparity-gradient detectors) is the most likely cause of stereo slant contrast.
Topics: Humans; Depth Perception; Contrast Sensitivity; Photic Stimulation; Vision, Binocular
PubMed: 38683571
DOI: 10.1167/jov.24.4.24 -
Cerebral Cortex (New York, N.Y. : 1991) Oct 2022Much of our flexible behavior is dependent on responding efficiently to relevant information while discarding irrelevant information. Little is known, however, about how...
Much of our flexible behavior is dependent on responding efficiently to relevant information while discarding irrelevant information. Little is known, however, about how neural pathways governing sensory-motor associations can rapidly switch to accomplish such flexibility. Here, we addressed this question by electrically microstimulating middle temporal (MT) neurons selective for both motion direction and binocular disparity in monkeys switching between direction and depth discrimination tasks. Surprisingly, we frequently found that the observed psychophysical bias precipitated by delivering microstimulation to neurons whose preferred direction and depth were related to opposite choices in the two tasks was substantially shifted toward a specific movement. Furthermore, these effects correlated with behavioral switching performance. Our findings suggest that the outputs of sensory signals are task specific and that irrelevant sensory-motor pathways are gated depending on task demand so as to accomplish rapid attentional switching.
Topics: Vision Disparity; Neurons; Employment; Motion Perception; Photic Stimulation
PubMed: 35088074
DOI: 10.1093/cercor/bhab508 -
Scientific Reports Sep 2022Accurate shape perception is critical for object perception, identification, manipulation, and recreation. Humans are capable of making judgements of both objective...
Accurate shape perception is critical for object perception, identification, manipulation, and recreation. Humans are capable of making judgements of both objective (physical) and projective (retinal) shape. Objective judgements benefit from a global approach by incorporating context to overcome the effects of viewing angle on an object's shape, whereas projective judgements benefit from a local approach to filter out contextual information. Realistic drawing skill requires projective judgements of 3D targets to accurately depict 3D shape on a 2D surface, thus benefiting from a local approach. The current study used a shape perception task that comprehensively tests the effects of context on shape perception, in conjunction with a drawing task and several possible measures of local processing bias, to show that the perceptual basis of drawing skill in neurotypical adults is not due to a local processing bias. Perceptual flexibility, the ability to process local or global information as needed, is discussed as a potential mechanism driving both accurate shape judgements and realistic drawing.
Topics: Adult; Bias; Depth Perception; Form Perception; Humans; Perception
PubMed: 36050496
DOI: 10.1038/s41598-022-18858-6 -
Cerebral Cortex (New York, N.Y. : 1991) May 2023An object's identity can influence depth-position judgments. The mechanistic underpinnings underlying this phenomenon are largely unknown. Here, we asked whether... (Randomized Controlled Trial)
Randomized Controlled Trial
An object's identity can influence depth-position judgments. The mechanistic underpinnings underlying this phenomenon are largely unknown. Here, we asked whether context-dependent modulations of stereoscopic depth perception are expertise dependent. In 2 experiments, we tested whether training that attaches meaning (i.e. classification labels) to otherwise novel, stereoscopically presented objects changes observers' sensitivity for judging their depth position. In Experiment 1, observers were randomly assigned to 3 groups: a Greeble-classification training group, an orientation-discrimination training group, or a no-training group, and were tested on their stereoscopic depth sensitivity before and after training. In Experiment 2, participants were tested before and after training while fMRI responses were concurrently imaged. Behaviorally, stereoscopic performance was significantly better following Greeble-classification (but not orientation-discrimination, or no-) training. Using the fMRI data, we trained support vector machines to predict whether the data were from the pre- or post-training sessions. Results indicated that classification accuracies in V4 were higher for the Greeble-classification group as compared with the orientation-discrimination group for which accuracies were at chance level. Furthermore, classification accuracies in V4 were negatively correlated with response times for Greeble identification. We speculate that V4 is implicated in an expertise-dependent, object-tuning manner that allows it to better guide stereoscopic depth retrieval.
Topics: Humans; Depth Perception; Reaction Time
PubMed: 36786066
DOI: 10.1093/cercor/bhad026 -
Annual Review of Vision Science Sep 2021Most animals have at least some binocular overlap, i.e., a region of space that is viewed by both eyes. This reduces the overall visual field and raises the problem of... (Review)
Review
Most animals have at least some binocular overlap, i.e., a region of space that is viewed by both eyes. This reduces the overall visual field and raises the problem of combining two views of the world, seen from different vantage points, into a coherent whole. However, binocular vision also offers many potential advantages, including increased ability to see around obstacles and increased contrast sensitivity. One particularly interesting use for binocular vision is comparing information from both eyes to derive information about depth. There are many different ways in which this might be done, but in this review, I refer to them all under the general heading of stereopsis. This review examines the different possible uses of binocular vision and stereopsis and compares what is currently known about the neural basis of stereopsis in different taxa. Studying different animals helps us break free of preconceptions stemming from the way that stereopsis operates in human vision and provides new insights into the different possible forms of stereopsis.
Topics: Animals; Contrast Sensitivity; Depth Perception; Vision, Binocular; Vision, Ocular
PubMed: 34283925
DOI: 10.1146/annurev-vision-093019-113212 -
Investigative Ophthalmology & Visual... Jun 2021We introduce a set of dichoptic training tasks that differ in terms of (1) the presence of external noise and (2) the visual feature implicated (motion, orientation),... (Randomized Controlled Trial)
Randomized Controlled Trial
PURPOSE
We introduce a set of dichoptic training tasks that differ in terms of (1) the presence of external noise and (2) the visual feature implicated (motion, orientation), examining the generality of training effects between the different training and test cues and their capacity for driving changes in sensory eye dominance and stereoscopic depth perception.
METHODS
We randomly assigned 116 normal-sighted observers to five groups (four training groups and one no training group). All groups completed both pre- and posttests, during which they were tested on dichoptic motion and orientation tasks under noisy and noise-free conditions, as well as a binocular phase combination task and two depth tasks to index sensory eye dominance and binocular function. Training groups received visual training on one of the four dichoptic tasks over 3 consecutive days.
RESULTS
Training under noise-free conditions supported generalization of learning to noise-free tasks involving an untrained feature. By contrast, there was a symmetric learning transfer between the signal-noise and no-noise tasks within the same visual feature. Further, training on all tasks reduced sensory eye dominance but did not improve depth perception.
CONCLUSIONS
Training-driven changes in sensory eye balance do not depend on the stimulus feature or whether the training entails the presence of external noise. We conjecture that dichoptic visual training acts to balance interocular suppression before or at the site of binocular combination.
Topics: Adult; Contrast Sensitivity; Cues; Depth Perception; Discrimination Learning; Dominance, Ocular; Female; Humans; Male; Noise; Outcome Assessment, Health Care; Photic Stimulation; Sensory Thresholds; Signal Detection, Psychological; Task Performance and Analysis; Vision, Binocular; Visual Perception
PubMed: 34106211
DOI: 10.1167/iovs.62.7.12 -
Journal of Cataract and Refractive... Feb 2020
Topics: Biometry; Clinical Competence; Depth Perception; Humans; Lens Implantation, Intraocular; Multifocal Intraocular Lenses; Optics and Photonics; Presbyopia; Prosthesis Design
PubMed: 32126026
DOI: 10.1097/j.jcrs.0000000000000128 -
Optics Express Mar 2020Foveation and (de)focus are two important visual factors in designing near eye displays. Foveation can reduce computational load by lowering display details towards the...
Foveation and (de)focus are two important visual factors in designing near eye displays. Foveation can reduce computational load by lowering display details towards the visual periphery, while focal cues can reduce vergence-accommodation conflict thereby lessening visual discomfort in using near eye displays. We performed two psychophysical experiments to investigate the relationship between foveation and focus cues. The first study measured blur discrimination sensitivity as a function of visual eccentricity, where we found discrimination thresholds significantly lower than previously reported. The second study measured depth discrimination threshold where we found a clear dependency on visual eccentricity. We discuss the study results and suggest further investigation.
Topics: Adult; Depth Perception; Humans; Middle Aged; Photic Stimulation; Sensory Thresholds; Visual Perception; Young Adult
PubMed: 32225914
DOI: 10.1364/OE.28.006734