The Experts below are selected from a list of 7011 Experts worldwide ranked by ideXlab platform
Dennis M Levi - One of the best experts on this subject based on the ideXlab platform.
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transfer of perceptual learning from local Stereopsis to global Stereopsis in adults with amblyopia a preliminary study
Frontiers in Neuroscience, 2021Co-Authors: Michael A Silver, Adrien Chopin, Yasha Sheynin, Jian Ding, Dennis M LeviAbstract:It has long been debated whether the analysis of global and local stereoscopic depth is performed by one or separate systems. Global Stereopsis requires the visual system to solve a complex binocular matching problem to obtain a coherent percept of depth. In contrast, local Stereopsis requires only a simple matching of similar image features. In this case series, we recruited 5 adults with amblyopia who lacked global Stereopsis and trained them on a computerized local-disparity stereoscopic depth task for an average of 12 hours. Three out of five (60%) participants recovered fine global stereoscopic vision. Those who recovered tended to start the training with better initial performance on the local-disparity task, to have less severe amblyopia, and to improve more on the local-disparity training task. The transfer of learning from local Stereopsis to global Stereopsis is compatible with an interacting two-stage model.
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monocular blur alters the tuning characteristics of Stereopsis for spatial frequency and size
Royal Society Open Science, 2016Co-Authors: Ashley Craven, Dennis M Levi, Truyet Tran, Kevin GustafsonAbstract:Our sense of depth perception is mediated by spatial filters at different scales in the visual brain; low spatial frequency channels provide the basis for coarse Stereopsis, whereas high spatial frequency channels provide for fine Stereopsis. It is well established that monocular blurring of vision results in decreased stereoacuity. However, previous studies have used tests that are broadband in their spatial frequency content. It is not yet entirely clear how the processing of Stereopsis in different spatial frequency channels is altered in response to binocular input imbalance. Here, we applied a new stereoacuity test based on narrow-band Gabor stimuli. By manipulating the carrier spatial frequency, we were able to reveal the spatial frequency tuning of Stereopsis, spanning from coarse to fine, under blurred conditions. Our findings show that increasing monocular blur elevates stereoacuity thresholds ‘selectively’ at high spatial frequencies, gradually shifting the optimum frequency to lower spatial frequencies. Surprisingly, Stereopsis for low frequency targets was only mildly affected even with an acuity difference of eight lines on a standard letter chart. Furthermore, we examined the effect of monocular blur on the size tuning function of Stereopsis. The clinical implications of these findings are discussed.
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Stereopsis and amblyopia: A mini-review
Vision Research, 2015Co-Authors: Dennis M Levi, David C Knill, Daphne BavelierAbstract:Amblyopia is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experience early in life. Amblyopia is clinically important because it is a major cause of vision loss in infants and young children. Amblyopia is also of basic interest because it reflects the neural impairment that occurs when normal visual development is disrupted. Amblyopia provides an ideal model for understanding when and how brain plasticity may be harnessed for recovery of function. Over the past two decades there has been a rekindling of interest in developing more effective methods for treating amblyopia, and for extending the treatment beyond the critical period, as exemplified by new clinical trials and new basic research studies. The focus of this review is on Stereopsis and its potential for recovery. Impaired stereoscopic depth perception is the most common deficit associated with amblyopia under ordinary (binocular) viewing conditions (Webber & Wood, 2005). Our review of the extant literature suggests that this impairment may have a substantial impact on visuomotor tasks, difficulties in playing sports in children and locomoting safely in older adults. Furthermore, impaired Stereopsis may also limit career options for amblyopes. Finally, Stereopsis is more impacted in strabismic than in anisometropic amblyopia. Our review of the various approaches to treating amblyopia (patching, perceptual learning, videogames) suggests that there are several promising new approaches to recovering Stereopsis in both anisometropic and strabismic amblyopes. However, recovery of stereoacuity may require more active treatment in strabismic than in anisometropic amblyopia. Individuals with strabismic amblyopia have a very low probability of improvement with monocular training; however they fare better with dichoptic training than with monocular training, and even better with direct stereo training.
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recovery of Stereopsis through perceptual learning in human adults with abnormal binocular vision
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Jian Ding, Dennis M LeviAbstract:Stereopsis, the perception of depth based on the disparity of the images projected to the retinas of the two eyes, is an important process in our three-dimensional world; however, 3–5% of the population is stereoblind or has seriously impaired stereovision. Here we provide evidence for the recovery of Stereopsis through perceptual learning, the repetitive practice of a demanding visual task, in human adults long deprived of normal binocular vision. We used a training paradigm that combines monocular cues that were correlated perfectly with the disparity cues. Following perceptual learning (thousands of trials) with stereoscopic gratings, five adults who initially were stereoblind or stereoanomalous showed substantial recovery of Stereopsis, both on psychophysical tests with stimuli that contained no monocular cues and on clinical testing. They reported that depth “popped out” in daily life, and enjoyed 3D movies for the first time. After training, stereo tests with dynamic random-dot stereograms and band-pass noise revealed the properties of the recovered Stereopsis: It has reduced resolution and precision, although it is based on perceiving depth by detecting binocular disparity. We conclude that some human adults deprived of normal binocular vision can recover Stereopsis at least partially.
David J. Kriegman - One of the best experts on this subject based on the ideXlab platform.
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toward a stratification of helmholtz Stereopsis
Computer Vision and Pattern Recognition, 2003Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:Helmholtz Stereopsis has been previously introduced as a surface reconstruction technique that does not assume a model of surface reflectance. This technique relies on the use of multiple cameras and light sources, and it has been shown to be effective when the camera and source positions are known. Here, we take a stratified look at uncalibrated Helmholtz Stereopsis. We derive a photometric matching constraint that can be used to establish correspondence without any knowledge of the cameras and sources (except that they are co-located), and we determine conditions under which we can obtain affine and metric reconstructions. An implementation and experimental results are presented.
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Helmholtz Stereopsis: Exploiting Reciprocity for Surface Reconstruction
International Journal of Computer Vision, 2002Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:We present a method—termed Helmholtz Stereopsis—for reconstructing the geometry of objects from a collection of images. Unlike existing methods for surface reconstruction (e.g., stereo vision, structure from motion, photometric Stereopsis), Helmholtz Stereopsis makes no assumptions about the nature of the bidirectional reflectance distribution functions (BRDFs) of objects. This new method of multinocular Stereopsis exploits Helmholtz reciprocity by choosing pairs of light source and camera positions that guarantee that the ratio of the emitted radiance to the incident irradiance is the same for corresponding points in the two images. The method provides direct estimates of both depth and surface normals, and consequently weds the advantages of both conventional Stereopsis and photometric Stereopsis. Results from our implementation lend empirical support to our technique.
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helmholtz Stereopsis exploiting reciprocity for surface reconstruction
European Conference on Computer Vision, 2002Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:We present a method - termed Helmholtz Stereopsis - for reconstructing the geometry of objects from a collection of images. Unlike most existing methods for surface reconstruction (e.g., stereo vision, structure from motion, photometric stereo), Helmholtz Stereopsis makes no assumptions about the nature of the bidirectional reflectance distribution functions (BRDFs) of objects. This new method of multinocular Stereopsis exploits Helmholtz reciprocity by choosing pairs of light source and camera positions that guarantee that the ratio of the emitted radiance to the incident irradiance is the same for corresponding points in the two images. The method provides direct estimates of both depth and field of surface normals, and consequently weds the advantages of both conventional and photometric Stereopsis. Results from our implementations lend empirical support to our technique.
Stephen Grossberg - One of the best experts on this subject based on the ideXlab platform.
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Stereopsis and 3d surface perception by spiking neurons in laminar cortical circuits a method for converting neural rate models into spiking models
Neural Networks, 2012Co-Authors: Yongqiang Cao, Stephen GrossbergAbstract:A laminar cortical model of Stereopsis and 3D surface perception is developed and simulated. The model shows how spiking neurons that interact in hierarchically organized laminar circuits of the visual cortex can generate analog properties of 3D visual percepts. The model describes how monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the LGN and cortical areas V1, V2, and V4. It proposes how interactions between layers 4, 3B, and 2/3 in V1 and V2 contribute to Stereopsis, and how binocular and monocular information combine to form 3D boundary and surface representations. The model suggests how surface-to-boundary feedback from V2 thin stripes to pale stripes helps to explain how computationally complementary boundary and surface formation properties lead to a single consistent percept, eliminate redundant 3D boundaries, and trigger figure-ground perception. The model also shows how false binocular boundary matches may be eliminated by Gestalt grouping properties. In particular, the disparity filter, which helps to solve the correspondence problem by eliminating false matches, is realized using inhibitory interneurons as part of the perceptual grouping process by horizontal connections in layer 2/3 of cortical area V2. The 3D sLAMINART model simulates 3D surface percepts that are consciously seen in 18 psychophysical experiments. These percepts include contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind illusion, Stereopsis with polarity-reversed stereograms, da Vinci Stereopsis, and perceptual closure. The model hereby illustrates a general method of unlumping rate-based models that use the membrane equations of neurophysiology into models that use spiking neurons, and which may be embodied in VLSI chips that use spiking neurons to minimize heat production.
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a laminar cortical model of Stereopsis and three dimensional surface perception
CAS CNS Technical Report Series, 2010Co-Authors: Stephen Grossberg, Piers D L HoweAbstract:A laminar cortical model of Stereopsis and later stages of three-dimensional surface perception is proposed and simulated. The model describes boundary and surface interactions between LGN, V1, V2, and V4, and details how the interactions between layers 4, 3B, and 2/3A in V1 and V2 contribute to Stereopsis. In particular, the model clarifies how binocular and monocular information combine during binocular vision. Neural explanations are given for various psychophysical observations reported in studies on: contrast variations of dichoptic masking and the correspondence problem, da Vinci Stereopsis, Stereopsis with polarity-reversed stereograms, and various lightness illusions. By regulating physiology to psychophysics, the model is able to provide new functional insights and predictions about laminar cortical architecture.
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a laminar cortical model of Stereopsis and 3d surface perception closure and da vinci Stereopsis
Spatial Vision, 2005Co-Authors: Yongqiang Cao, Stephen GrossbergAbstract:A laminar cortical model of Stereopsis and 3D surface perception is developed and simulated. The model describes how monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the LGN and cortical areas V1, V2, and V4. It proposes how interactions between layers 4, 3B, and 2/3 in V1 and V2 contribute to Stereopsis, and how binocular and monocular information combine to form 3D boundary and surface representations. The model includes two main new developments: (1) It clarifies how surface-to-boundary feedback from V2 thin stripes to pale stripes helps to explain data about Stereopsis. This feedback has previously been used to explain data about 3D figure-ground perception. (2) It proposes that the binocular false match problem is subsumed under the Gestalt grouping problem. In particular, the disparity filter, which helps to solve the correspondence problem by eliminating false matches, is realized using inhibitory interneurons as part of the perceptual grouping process by horizontal connections in layer 2/3 of cortical area V2. The enhanced model explains all the psychophysical data previously simulated by Grossberg and Howe (2003), such as contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind illusion, Stereopsis with polarity-reversed stereograms, and da Vinci Stereopsis. It also explains psychophysical data about perceptual closure and variations of da Vinci Stereopsis that previous models cannot yet explain.
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a laminar cortical model of Stereopsis and three dimensional surface perception
Vision Research, 2003Co-Authors: Stephen Grossberg, Piers D L HoweAbstract:A laminar cortical model of Stereopsis and later stages of 3D surface perception is developed and simulated. The model describes how initial stages of monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the lateral geniculate nucleus and cortical areas V1, V2, and V4. In particular, it details how interactions between layers 4, 3B, and 2/3A in V1 and V2 contribute to Stereopsis, and clarifies how binocular and monocular information combine to form 3D boundary and surface representations. Along the way, the model modifies and significantly extends the disparity energy model. Neural explanations are given for psychophysical data concerning: contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind illusion, Stereopsis with polarity-reversed stereograms, da Vinci Stereopsis, and various lightness illusions. By relating physiology to psychophysics, the model provides new functional insights and predictions about laminar cortical architecture.
Todd E. Zickler - One of the best experts on this subject based on the ideXlab platform.
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toward a stratification of helmholtz Stereopsis
Computer Vision and Pattern Recognition, 2003Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:Helmholtz Stereopsis has been previously introduced as a surface reconstruction technique that does not assume a model of surface reflectance. This technique relies on the use of multiple cameras and light sources, and it has been shown to be effective when the camera and source positions are known. Here, we take a stratified look at uncalibrated Helmholtz Stereopsis. We derive a photometric matching constraint that can be used to establish correspondence without any knowledge of the cameras and sources (except that they are co-located), and we determine conditions under which we can obtain affine and metric reconstructions. An implementation and experimental results are presented.
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Helmholtz Stereopsis: Exploiting Reciprocity for Surface Reconstruction
International Journal of Computer Vision, 2002Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:We present a method—termed Helmholtz Stereopsis—for reconstructing the geometry of objects from a collection of images. Unlike existing methods for surface reconstruction (e.g., stereo vision, structure from motion, photometric Stereopsis), Helmholtz Stereopsis makes no assumptions about the nature of the bidirectional reflectance distribution functions (BRDFs) of objects. This new method of multinocular Stereopsis exploits Helmholtz reciprocity by choosing pairs of light source and camera positions that guarantee that the ratio of the emitted radiance to the incident irradiance is the same for corresponding points in the two images. The method provides direct estimates of both depth and surface normals, and consequently weds the advantages of both conventional Stereopsis and photometric Stereopsis. Results from our implementation lend empirical support to our technique.
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helmholtz Stereopsis exploiting reciprocity for surface reconstruction
European Conference on Computer Vision, 2002Co-Authors: Todd E. Zickler, P.n. Peter N Peter N Belhumeur, David J. KriegmanAbstract:We present a method - termed Helmholtz Stereopsis - for reconstructing the geometry of objects from a collection of images. Unlike most existing methods for surface reconstruction (e.g., stereo vision, structure from motion, photometric stereo), Helmholtz Stereopsis makes no assumptions about the nature of the bidirectional reflectance distribution functions (BRDFs) of objects. This new method of multinocular Stereopsis exploits Helmholtz reciprocity by choosing pairs of light source and camera positions that guarantee that the ratio of the emitted radiance to the incident irradiance is the same for corresponding points in the two images. The method provides direct estimates of both depth and field of surface normals, and consequently weds the advantages of both conventional and photometric Stereopsis. Results from our implementations lend empirical support to our technique.
Jenny C. A. Read - One of the best experts on this subject based on the ideXlab platform.
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binocular responsiveness of projection neurons of the praying mantis optic lobe in the frontal visual field
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2020Co-Authors: Ronny Rosner, Ghaith Tarawneh, Veronika Lukyanova, Jenny C. A. ReadAbstract:Praying mantids are the only insects proven to have stereoscopic vision (Stereopsis): the ability to perceive depth from the slightly shifted images seen by the two eyes. Recently, the first neurons likely to be involved in mantis Stereopsis were described and a speculative neuronal circuit suggested. Here we further investigate classes of neurons in the lobula complex of the praying mantis brain and their tuning to stereoscopically-defined depth. We used sharp electrode recordings with tracer injections to identify visual projection neurons with input in the optic lobe and output in the central brain. In order to measure binocular response fields of the cells the animals watched a vertical bar stimulus in a 3D insect cinema during recordings. We describe the binocular tuning of 19 neurons projecting from the lobula complex and the medulla to central brain areas. The majority of neurons (12/19) were binocular and had receptive fields for both eyes that overlapped in the frontal region. Thus, these neurons could be involved in mantis Stereopsis. We also find that neurons preferring different contrast polarity (bright vs dark) tend to be segregated in the mantis lobula complex, reminiscent of the segregation for small targets and widefield motion in mantids and other insects.
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second order cues to figure motion enable object detection during prey capture by praying mantises
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Vivek Nityananda, Diana Umeton, Adam Simmons, James Okeeffe, Jenny C. A. ReadAbstract:Detecting motion is essential for animals to perform a wide variety of functions. In order to do so, animals could exploit motion cues, including both first-order cues—such as luminance correlation over time—and second-order cues, by correlating higher-order visual statistics. Since first-order motion cues are typically sufficient for motion detection, it is unclear why sensitivity to second-order motion has evolved in animals, including insects. Here, we investigate the role of second-order motion in prey capture by praying mantises. We show that prey detection uses second-order motion cues to detect figure motion. We further present a model of prey detection based on second-order motion sensitivity, resulting from a layer of position detectors feeding into a second layer of elementary-motion detectors. Mantis Stereopsis, in contrast, does not require figure motion and is explained by a simpler model that uses only the first layer in both eyes. Second-order motion cues thus enable prey motion to be detected, even when perfectly matching the average background luminance and independent of the elementary motion of any parts of the prey. Subsequent to prey detection, processes such as Stereopsis could work to determine the distance to the prey. We thus demonstrate how second-order motion mechanisms enable ecologically relevant behavior such as detecting camouflaged targets for other visual functions including Stereopsis and target tracking.
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a novel form of stereo vision in the praying mantis
Current Biology, 2018Co-Authors: Vivek Nityananda, Ghaith Tarawneh, Sid Henriksen, Diana Umeton, Adam Simmons, Jenny C. A. ReadAbstract:Summary Stereopsis is the ability to estimate distance based on the different views seen in the two eyes [1–5]. It is an important model perceptual system in neuroscience and a major area of machine vision. Mammalian, avian, and almost all machine stereo algorithms look for similarities between the luminance-defined images in the two eyes, using a series of computations to produce a map showing how depth varies across the scene [3, 4, 6–14]. Stereopsis has also evolved in at least one invertebrate, the praying mantis [15–17]. Mantis Stereopsis is presumed to be simpler than vertebrates' [15, 18], but little is currently known about the underlying computations. Here, we show that mantis Stereopsis uses a fundamentally different computational algorithm from vertebrate Stereopsis—rather than comparing luminance in the two eyes' images directly, mantis Stereopsis looks for regions of the images where luminance is changing . Thus, while there is no evidence that mantis Stereopsis works at all with static images, it successfully reveals the distance to a moving target even in complex visual scenes with targets that are perfectly camouflaged against the background in terms of texture. Strikingly, these insects outperform human observers at judging stereoscopic distance when the pattern of luminance in the two eyes does not match. Insect Stereopsis has thus evolved to be computationally efficient while being robust to poor image resolution and to discrepancies in the pattern of luminance between the two eyes. Video Abstract
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Stereopsis in animals evolution function and mechanisms
The Journal of Experimental Biology, 2017Co-Authors: Vivek Nityananda, Jenny C. A. ReadAbstract:Stereopsis is the computation of depth information from views acquired simultaneously from different points in space. For many years, Stereopsis was thought to be confined to primates and other mammals with front-facing eyes. However, Stereopsis has now been demonstrated in many other animals, including lateral-eyed prey mammals, birds, amphibians and invertebrates. The diversity of animals known to have stereo vision allows us to begin to investigate ideas about its evolution and the underlying selective pressures in different animals. It also further prompts the question of whether all animals have evolved essentially the same algorithms to implement Stereopsis. If so, this must be the best way to do stereo vision, and should be implemented by engineers in machine Stereopsis. Conversely, if animals have evolved a range of stereo algorithms in response to different pressures, that could inspire novel forms of machine Stereopsis appropriate for distinct environments, tasks or constraints. As a first step towards addressing these ideas, we here review our current knowledge of stereo vision in animals, with a view towards outlining common principles about the evolution, function and mechanisms of stereo vision across the animal kingdom. We conclude by outlining avenues for future work, including research into possible new mechanisms of stereo vision, with implications for machine vision and the role of Stereopsis in the evolution of camouflage.
