scholarly journals Near-optimal combination of disparity across a log-polar scaled visual field

2019 ◽  
Author(s):  
Guido Maiello ◽  
Manuela Chessa ◽  
Peter J. Bex ◽  
Fabio Solari
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Depth Perception ◽  
Binocular Disparity ◽  
Spatial Scales ◽  
Visual Input ◽  
Depth Information ◽  
Central Vision

AbstractThe human visual system is foveated: we can see fine spatial details in central vision, whereas resolution is poor in our peripheral visual field, and this loss of resolution follows an approximately logarithmic decrease. Additionally, our brain organizes visual input in polar coordinates. Therefore, the image projection occurring between retina and primary visual cortex can be mathematically described by the log-polar transform. Here, we test and model how this space-variant visual processing affects how we process binocular disparity, a key component of human depth perception. We observe that the fovea preferentially processes disparities at fine spatial scales, whereas the visual periphery is tuned for coarse spatial scales, in line with the naturally occurring distributions of depths and disparities in the real-world. We further show that the visual field integrates disparity information across the visual field, in a near-optimal fashion. We develop a foveated, log-polar model that mimics the processing of depth information in primary visual cortex and that can process disparity directly in the cortical domain representation. This model takes real images as input and recreates the observed topography of disparity sensitivity in man. Our findings support the notion that our foveated, binocular visual system has been moulded by the statistics of our visual environment.Author summaryWe investigate how humans perceive depth from binocular disparity at different spatial scales and across different regions of the visual field. We show that small changes in disparity-defined depth are detected best in central vision, whereas peripheral vision best captures the coarser structure of the environment. We also demonstrate that depth information extracted from different regions of the visual field is combined into a unified depth percept. We then construct an image-computable model of disparity processing that takes into account how our brain organizes the visual input at our retinae. The model operates directly in cortical image space, and neatly accounts for human depth perception across the visual field.

scholarly journals Unique spatial integration in mouse primary visual cortex and higher visual areas

2019 ◽  
Author(s):  
Kevin A. Murgas ◽  
Ashley M. Wilson ◽  
Valerie Michael ◽  
Lindsey L. Glickfeld
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Spatial Information ◽  
Spatial Scales ◽  
Spatial Integration ◽  
Global Features ◽  
Wide Range ◽  
Visual Areas ◽  
Higher Visual Areas

AbstractNeurons in the visual system integrate over a wide range of spatial scales. This diversity is thought to enable both local and global computations. To understand how spatial information is encoded across the mouse visual system, we use two-photon imaging to measure receptive fields in primary visual cortex (V1) and three downstream higher visual areas (HVAs): LM (lateromedial), AL (anterolateral) and PM (posteromedial). We find significantly larger receptive field sizes and less surround suppression in PM than in V1 or the other HVAs. Unlike other visual features studied in this system, specialization of spatial integration in PM cannot be explained by specific projections from V1 to the HVAs. Instead, our data suggests that distinct connectivity within PM may support the area’s unique ability to encode global features of the visual scene, whereas V1, LM and AL may be more specialized for processing local features.

scholarly journals Cortical reorganization of the visual system in post-stroke hemianopia studied with fMRI

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 334-334
Author(s):  
Gereon Nelles ◽  
Guido Widmann ◽  
Joachim Esser ◽  
Anette Meistrowitz ◽  
Johannes Weber ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Visual Stimuli ◽  
Checkerboard Pattern ◽  
Partial Recovery ◽  
Area 18 ◽  
Area 19 ◽  
Stimulation Of

102 Introduction: Restitution of unilateral visual field defects following occipital cortex lesions occurs rarely. Partial recovery, however, can be observed in patients with incomplete lesion of the visual cortex. Our objective was to study the neuroplastic changes in the visual system that underlie such recovery. Methods and Results: Six patients with a left PCA-territory cortical stroke and 6 healthy control subjects were studied during rest and during visual stimulation using a 1.5 T fMRI with a 40 mT gradient. Visual stimuli were projected with a laptop computer onto a 154 x 115 cm screen, placed 90 cm in front of the gantry. Subjects were asked to fixate a red point in the center of the screen during both conditions. During stimulation, a black-and-white checkerboard pattern reversal was presented in each hemifield. For each side, 120 volumes of 48 contiguous axial fMRI images were obtained during rest and during hemifield stimulation in alternating order (60 volumes for each condition). Significant differences of rCBF between stimulation and rest were assessed as group analyses using statistical parametric mapping (SPM 99; p<0.01, corrected for multiple comparison). In controls, strong increases of rCBF (Z=7.6) occurred in the contralateral primary visual cortex V1 (area 17) and in V3a (area 18) and V5 (area 19). No differences were found between the right and left side in controls. During stimulation of the unaffected (left) visual field in hemianopic patients, activation occurred in contralateral V1, but the strongest increases of rCBF (Z>10) were seen in contralateral V3a (area 18) and V5 (area 19). During stimulation of the hemianopic (right) visual field, no activation was found in the primary visual cortex of either hemisphere. The most significant activation (Z=9.2) was seen in the ipsilateral V3a and V5 areas, and contralateral (left) V3a. Conclusions: Partial recovery from hemianopia is associated with strong ipsilateral activation of the visual system. Processing of visual stimuli in the hemianopic side spares the primary visual cortex and may involve recruitment of neurons in ipsilateral (contralesional) areas V3a and V5.

scholarly journals Retinotopic remapping of the visual system in deaf adults

2020 ◽  
Author(s):  
Alexandra T. Levine ◽  
Kate Yuen ◽  
André Gouws ◽  
Alex R. Wade ◽  
Antony B. Morland ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Lateral Geniculate Nucleus ◽  
Primary Visual Cortex ◽  
Central Visual Field ◽  
Auditory Cues ◽  
Lateral Geniculate ◽  
Visual Maps ◽  
Deaf Adults

AbstractDeaf individuals rely on visual rather than auditory cues to detect events in the periphery, putting a greater demand on neural resources for vision. Comparing visual maps in the brains of early deaf and hearing adults, we found a redistribution of neural resources in the lateral geniculate nucleus and primary visual cortex, with larger representations of the periphery, at a cost of smaller representations of the central visual field.

Man, Monkey, and Blindsight

1998 ◽  
Vol 4 (4) ◽  
pp. 227-230 ◽  
Author(s):  
Tirin Moore ◽  
Hillary R. Rodman ◽  
Charles G. Gross
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Visual Function ◽  
Forced Choice ◽  
Neural Mechanisms ◽  
Residual Vision ◽  
Choice Testing

The visual function that survives damage to the primary visual cortex (V1) in humans is often unaccompanied by awareness. This type of residual vision, called “blindsight,” has raised considerable interest because it implies a separation of conscious from unconscious vision mechanisms. The monkey visual system has proven to be a useful model in elucidating the possible neural mechanisms of residual vision and blindsight in humans. Clear similarities, however, between the phenomenology of human and monkey residual vision have only recently become evident. This article summarizes parallels between residual vision in monkeys and humans with damage to V1. These parallels Include the tendency of the remaining vision to require forced-choice testing and the fact that more robust residual vision remains when V1 damage is sustained early in life. NEUROSCIENTIST 4:227–230

Interaction between Colour and Depth Channels in Transparent Colour Perception

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 115-115
Author(s):  
K Okajima ◽  
M Takase ◽  
S Takahashi
Keyword(s):  
Information Processing ◽  
Visual System ◽  
Binocular Disparity ◽  
Depth Information ◽  
Apparent Depth ◽  
Colour Perception

Two colours can be perceived at one location on overlapping planes only when the front plane is transparent. This phenomenon suggests that colour information processing is not independent of depth information processing and vice versa. To investigate the interaction between colour and depth channels, we used colour stimuli and binocular parallax to identify the conditions for transparency. Each stimulus, presented on a CRT to one eye, consisted of a centre patch and a surround. Binocular disparity was set so that the centre patch could be seen behind the surround. However, the surround appears to be behind the centre patch when the surround is perceived as an opaque plane. We examined several combinations of basic colours for the centre patch and surround. The surround luminance was constant at 1.0 cd m−2 and the luminance of the centre was varied. Subjects used the apparent depth of the surround to report whether or not transparency occurred. The results show two types of transparency: ‘bright-centre transparency’ and ‘dark-centre transparency’. We found that the range of centre luminances which yield transparency depends on the combination of centre and surround colours, ie influences of brightness and colour opponency were found. We conclude that there is interaction between colour and depth channels in the visual system.

scholarly journals Blindsight and Unconscious Vision: What They Teach Us about the Human Visual System

2016 ◽  
Vol 23 (5) ◽  
pp. 529-541 ◽  
Author(s):  
Sara Ajina ◽  
Holly Bridge
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Human Visual System ◽  
Visual Information ◽  
Visual Loss ◽  
Physiological Conditions ◽  
The World ◽  
The Brain

Damage to the primary visual cortex removes the major input from the eyes to the brain, causing significant visual loss as patients are unable to perceive the side of the world contralateral to the damage. Some patients, however, retain the ability to detect visual information within this blind region; this is known as blindsight. By studying the visual pathways that underlie this residual vision in patients, we can uncover additional aspects of the human visual system that likely contribute to normal visual function but cannot be revealed under physiological conditions. In this review, we discuss the residual abilities and neural activity that have been described in blindsight and the implications of these findings for understanding the intact system.

Quantitative Measurement of Human Visual Characteristic on Depth Perception with Using Random-Dot Stimulus

2000 ◽  
Vol 44 (21) ◽  
pp. 3-500-3-500
Author(s):  
Jing-Long Wu ◽  
Kazuyoshi Tsukamoto
Keyword(s):  
Depth Perception ◽  
Quantitative Measurement ◽  
Binocular Disparity ◽  
Experimental Results ◽  
Depth Information ◽  
Head Mounted Display ◽  
Visual Characteristic

Human interactive characteristic between the binocular disparity and the occlusion for depth perception is measured with using random-dot stimulus. The experimental results suggested that if the binocular disparity is set at a proper value, the depth information is mainly obtained from the cue of the binocular disparity, and if the occlusion ratio is larger than some constant value the depth information is obtained from the cue of the occlusion. Based on the experimental results, we can find a method to make images with depth information in the Head Mounted Display (HMD) when the cues of the binocular disparity and the occlusion are concurrently used.

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