scholarly journals Processing of the S-cone signals in the early visual cortex of primates

2013 ◽  
Vol 31 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Youping Xiao
Keyword(s):  
Visual Cortex ◽  
Color Vision ◽  
Short Wavelength ◽  
Nonhuman Primates ◽  
Striate Cortex ◽  
Color Perception ◽  
Visual Pathway ◽  
Visual Features ◽  
Area V2 ◽  
Early Visual Cortex

AbstractThe short-wavelength-sensitive (S) cones play an important role in color vision of primates, and may also contribute to the coding of other visual features, such as luminance and motion. The color signals carried by the S cones and other cone types are largely separated in the subcortical visual pathway. Studies on nonhuman primates or humans have suggested that these signals are combined in the striate cortex (V1) following a substantial amplification of the S-cone signals in the same area. In addition to reviewing these studies, this review describes the circuitry in V1 that may underlie the processing of the S-cone signals and the dynamics of this processing. It also relates the interaction between various cone signals in V1 to the results of some psychophysical and physiological studies on color perception, which leads to a discussion of a previous model, in which color perception is produced by a multistage processing of the cone signals. Finally, I discuss the processing of the S-cone signals in the extrastriate area V2.

scholarly journals Color perception matches selectivity in human early visual cortex

2020 ◽  
Vol 13 (1) ◽  
pp. 253-255
Author(s):  
Qian Wang ◽  
Lu Luo ◽  
Jing Wang ◽  
Guoming Luan
Keyword(s):  
Visual Cortex ◽  
Color Perception ◽  
Early Visual Cortex

scholarly journals Disentangling the representation of identity from head view along the human face processing pathway

2016 ◽  
Author(s):  
J. Swaroop Guntupalli ◽  
Kelsey G. Wheeler ◽  
M. Ida Gobbini
Keyword(s):  
Visual Cortex ◽  
Frontal Cortex ◽  
Face Perception ◽  
Face Processing ◽  
Visual Features ◽  
Fusiform Face Area ◽  
Invariant Representation ◽  
Face Area ◽  
Early Visual Cortex ◽  
Occipital Face Area

AbstractNeural models of a distributed system for face perception implicate a network of regions in the ventral visual stream for recognition of identity. Here, we report an fMRI neural decoding study in humans that shows that this pathway culminates in a right inferior frontal cortex face area (rIFFA) with a representation of individual identities that has been disentangled from variable visual features in different images of the same person. At earlier stages in the pathway, processing begins in early visual cortex and the occipital face area (OFA) with representations of head view that are invariant across identities, and proceeds to an intermediate level of representation in the fusiform face area (FFA) in which identity is emerging but still entangled with head view. Three-dimensional, view-invariant representation of identities in the rIFFA may be the critical link to the extended system for face perception, affording activation of person knowledge and emotional responses to familiar faces.Significance StatementIn this fMRI decoding experiment, we address how face images are processed in successive stages to disentangle the view-invariant representation of identity from variable visual features. Representations in early visual cortex and the occipital face area distinguish head views, invariant across identities. An intermediate level of representation in the fusiform face area distinguishes identities but still is entangled with head view. The face-processing pathway culminates in the right inferior frontal area with representation of view-independent identity. This paper clarifies the homologies between the human and macaque face processing systems. The findings show further, however, the importance of the inferior frontal cortex in decoding face identity, a result that has not yet been reported in the monkey literature.

scholarly journals Cortical Double-Opponent Cells in Color Perception: Perceptual Scaling and Chromatic Visual Evoked Potentials

i-Perception ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 204166951775271 ◽  
Author(s):  
Valerie Nunez ◽  
Robert M. Shapley ◽  
James Gordon
Keyword(s):  
Visual Cortex ◽  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Color Perception ◽  
Neural Substrates ◽  
Response Dynamics ◽  
Early Visual Cortex ◽  
Visual Evoked

In the early visual cortex V1, there are currently only two known neural substrates for color perception: single-opponent and double-opponent cells. Our aim was to explore the relative contributions of these neurons to color perception. We measured the perceptual scaling of color saturation for equiluminant color checkerboard patterns (designed to stimulate double-opponent neurons preferentially) and uniformly colored squares (designed to stimulate only single-opponent neurons) at several cone contrasts. The spatially integrative responses of single-opponent neurons would produce the same response magnitude for checkerboards as for uniform squares of the same space-averaged cone contrast. However, perceived saturation of color checkerboards was higher than for the corresponding squares. The perceptual results therefore imply that double-opponent cells are involved in color perception of patterns. We also measured the chromatic visual evoked potential (cVEP) produced by the same stimuli; checkerboard cVEPs were much larger than those for corresponding squares, implying that double-opponent cells also contribute to the cVEP response. The total Fourier power of the cVEP grew sublinearly with cone contrast. However, the 6-Hz Fourier component’s power grew linearly with contrast-like saturation perception. This may also indicate that cortical coding of color depends on response dynamics.

scholarly journals Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude

2018 ◽  
Vol 30 (12) ◽  
pp. 1788-1802 ◽  
Author(s):  
Michele Fornaciai ◽  
Joonkoo Park
Keyword(s):  
Visual Cortex ◽  
Neural Activity ◽  
Stimulus Onset ◽  
Neural Representation ◽  
Numerical Magnitude ◽  
Sensory Representation ◽  
Area V2 ◽  
Early Visual Cortex ◽  
Multivariate Pattern ◽  
Number Perception

Recent studies have demonstrated that the numerosity of visually presented dot arrays is represented in low-level visual cortex extremely early in latency. However, whether or not such an early neural signature reflects the perceptual representation of numerosity remains unknown. Alternatively, such a signature may indicate the raw sensory representation of the dot-array stimulus before becoming the perceived representation of numerosity. Here, we addressed this question by using the connectedness illusion, whereby arrays with pairwise connected dots are perceived to be less numerous compared with arrays containing isolated dots. Using EEG and fMRI in two independent experiments, we measured neural responses to dot-array stimuli comprising 16 or 32 dots, either isolated or pairwise connected. The effect of connectedness, which reflects the segmentation of the visual stimulus into perceptual units, was observed in the neural activity after 150 msec post stimulus onset in the EEG experiment and in area V3 in the fMRI experiment using a multivariate pattern analysis. In contrast, earlier neural activity before 100 msec and in area V2 was strictly modulated by numerosity regardless of connectedness, suggesting that this early activity reflects the sensory representation of a dot array before perceptual segmentation. Our findings thus demonstrate that the neural representation for numerosity in early visual cortex is not sufficient for visual number perception and suggest that the perceptual encoding of numerosity occurs at or after the segmentation process that takes place later in area V3.

scholarly journals Solving visual correspondence between the two eyes via domain-based population encoding in nonhuman primates

2017 ◽  
Vol 114 (49) ◽  
pp. 13024-13029 ◽  
Author(s):  
Gang Chen ◽  
Haidong D. Lu ◽  
Hisashi Tanigawa ◽  
Anna W. Roe
Keyword(s):  
Visual Cortex ◽  
Nonhuman Primates ◽  
Population Coding ◽  
Stereoscopic Vision ◽  
Imaging Data ◽  
Area V2 ◽  
Visual Correspondence ◽  
Visual Cortical Area ◽  
Visual Cortical ◽  
The Brain

Stereoscopic vision depends on correct matching of corresponding features between the two eyes. It is unclear where the brain solves this binocular correspondence problem. Although our visual system is able to make correct global matches, there are many possible false matches between any two images. Here, we use optical imaging data of binocular disparity response in the visual cortex of awake and anesthetized monkeys to demonstrate that the second visual cortical area (V2) is the first cortical stage that correctly discards false matches and robustly encodes correct matches. Our findings indicate that a key transformation for achieving depth perception lies in early stages of extrastriate visual cortex and is achieved by population coding.

scholarly journals Novel Visual Perceptual Phenomenon in Isoluminant Bi-Coloured Square-Wave Gratings

2019 ◽  
Author(s):  
Azaac Wei En Tan ◽  
Gerrit W Maus
Keyword(s):  
Visual Cortex ◽  
Spatial Frequency ◽  
Human Perception ◽  
Visual Pathway ◽  
Colour Perception ◽  
Future Directions ◽  
Square Wave ◽  
Early Visual Cortex ◽  
Illusory Percept ◽  
Perceptual Phenomenon

Visual illusions, beyond their ability to entertain, reveal the “flaws” and limits of human perception, and how our visual senses can be fooled. In this study, we present a novel illusory percept generated by isoluminant bi-coloured square-wave gratings. We document the physical characteristics of the stimuli that affect the strength of the illusion and the illusory colours perceived, and consider potential mechanisms underlying this phenomenon. In line with our hypotheses, the results reveal that the strength of the illusion varies with the spatial frequency of the grating, and that the illusory percept is motion-dependent. Analysis of the illusory colours perceived reveals a relationship between the stimulus colours and the illusory colours perceived. This relationship demonstrates integration of the typically independent red-green parvocellular and blue-yellow koniocellular channels in the visual pathway. Overall, this pioneering study points towards a new mechanism of colour perception and integration, possibly in the early visual cortex. Possible future directions of research employing these coloured square-wave gratings are discussed.

scholarly journals Representation of Color, Form, and their Conjunction across the Human Ventral Visual Pathway

2020 ◽  
Author(s):  
JohnMark Taylor ◽  
Yaoda Xu
Keyword(s):  
Visual Cortex ◽  
Temporal Cortex ◽  
Visual Pathway ◽  
Significant Feature ◽  
Form Processing ◽  
Neuroscience Research ◽  
Ventral Visual Pathway ◽  
Early Visual Cortex ◽  
Form Feature ◽  
Interactive Coding

AbstractDespite decades of neuroscience research, our understanding of the relationship between color and form processing in the primate ventral visual pathway remains incomplete. Using fMRI multivoxel pattern analysis, this study examined the coding of color with both a simple form feature (orientation) and a mid-level form feature (curvature) in human early visual areas V1 to V4, posterior and central color regions, and shape areas in ventral and lateral occipito-temporal cortex. With the exception of the central color region (which showed color but not form decoding), successful color and form decoding was found in all other regions examined, even for color and shape regions showing univariate sensitivity to one feature. That said, all regions exhibited significant feature decoding biases, with decoding from color and shape regions largely consistent with their univariate preferences. Color and form are thus represented in neither a completely distributed nor a completely modular manner, but a biased distributed manner. Interestingly, coding of one feature in a brain region was always tolerant to changes in the other feature, indicating relative independence of color and form coding throughout the ventral visual cortex. Although evidence for interactive coding of color and form also existed, the effect was weak and only existed for color and orientation conjunctions in early visual cortex. No evidence for interactive coding of color and curvature was found. The predominant relationship between color and form coding in the human brain appears to be one of anatomical coexistence (in a biased distributed manner), but representational independence.

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