Visual Functions of Primate Area V4

Pasupathy, Anitha; Popovkina, Dina; Kim, Taekjun

doi:10.1146/annurev-vision-030320-041306

Cited by 60 publications

(53 citation statements)

References 148 publications

(152 reference statements)

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“…This process has been reported to occur in the ventral visual pathway (V1-V2-V4-IT) in a hierarchical manner ( Connor et al, 2007 ). The mid-level area V4 plays an important role in this process ( Roe et al, 2012 ; Pasupathy et al, 2020 ). Many V4 neurons selectively respond to curvatures ( Pasupathy and Connor, 1999 ) and complex shape features ( Desimone and Schein, 1987 ; Gallant et al, 1993 ; Kobatake and Tanaka, 1994 ).…”

Section: Introductionmentioning

confidence: 99%

Curvature-processing domains in primate V4

Tang

Song

Liu

et al. 2020

eLife

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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.

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Section: Introductionmentioning

confidence: 99%

Curvature-processing domains in primate V4

Tang

Song

Liu

et al. 2020

eLife

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“…Additionally, V4 neuronal responses depend on the joint stimulus statistics shown within their receptive fields, as in studies of selectivity for stimulus textures (Okazawa et al, 2017). Together, these studies suggest V4 neurons encode the relationship between spatially adjacent image features, in order to extract mid-level representations of object shape and surfaces (Desimone and Schein, 1987;Ghose and Ts'o, 1997;Hegde and Van Essen, 2006;Roe et al, 2012;Pasupathy et al, 2020). While each of these studies probes distinct forms of selectivity, together they reinforce the notion that V4 tuning might differ strongly for a small target stimulus within the receptive field when it appears in isolation or amid other nearby stimuli.…”

Section: Discussionmentioning

confidence: 87%

Feature representation under crowding in V1 and V4 neuronal populations

Henry

Kohn

2021

Preprint

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Visual perception depends strongly on spatial context. A profound example is visual crowding, whereby the presence of nearby stimuli impairs discriminability of object features. Despite extensive work on both perceptual crowding and the spatial integrative properties of visual cortical neurons, the link between these two aspects of visual processing remains unclear. To understand better the neural basis of crowding, we recorded simultaneously from neuronal populations in V1 and V4 of fixating macaque monkeys. We assessed the information about the orientation of a visual target available from the measured responses, both for targets presented in isolation and amid distractors. Both single neuron and population responses had less information about target orientation when distractors were present. Information loss was moderate in V1 and more substantial in V4. Information loss could be traced to systematic divisive and additive changes in neuronal tuning. Tuning changes were more severe in V4; in addition, tuning exhibited greater context-dependent distortions in V4, further restricting the ability of a fixed sensory readout strategy to extract accurate feature information across changing environments. Our results provide a direct test of crowding effects at different stages of the visual hierarchy, reveal how these effects alter the spiking activity of cortical populations by which sensory stimuli are encoded, and connect these changes to established mechanisms of neuronal spatial integration.

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“…Two fundamental properties of neurons in early visual cortex-collinear facilitation and flexible surround suppression-may provide critical building blocks for segmented object representations in later stages by enhancing the representation of collinear contours (Kapadia et al, 1995;Polat et al, 1998;Bakin et al, 2000;Bauer and Heinze, 2002) and contrasting texture regions (Blakemore and Tobin, 1972;Nelson and Frost, 1985;Knierim and van Essen, 1992;Kapadia et al, 1995;Levitt and Lund, 1997;Nothdurft et al, 1999;Cavanaugh et al, 2002;Coen-Cagli et al, 2015). These signals may enhance continuous contours at the expense of texture elements (Gheorghiu et al, 2014) and contribute to the emergence of object-based representations (Pasupathy et al, 2020). Thus, when there are sizable contrasts in color (as in our stimuli) or texture or long contours that bound objects, contextual modulations in early and midlevel processing stages may facilitate the enhanced representation of segmented objects in IT cortex.…”

Section: Segmented Representation Of Visual Scenesmentioning

confidence: 99%

Encoding of Partially Occluded and Occluding Objects in Primate Inferior Temporal Cortex

Namima

Pasupathy

2021

J. Neurosci.

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Object segmentation-the process of parsing visual scenes-is essential for object recognition and scene understanding. We investigated how responses of neurons in macaque inferior temporal (IT) cortex contribute to object segmentation under partial occlusion. Specifically, we asked whether IT responses to occluding and occluded objects are bound together as in the visual image or linearly separable reflecting their segmentation. We recorded the activity of 121 IT neurons while two male animals performed a shape discrimination task under partial occlusion. We found that for a majority (60%) of neurons, responses were enhanced by partial occlusion, but they were only weakly shape selective for the discriminanda at all levels of occlusion. Enhancement of IT responses in these neurons depended largely on the area of occlusion but only minimally on the color and shape of the occluding dots. In contrast to the above group of neurons, a sizable minority responded best to the unoccluded stimulus and showed strong selectivity for the shape of the discriminanda. In these neurons, response magnitude and shape selectivity declined with increasing levels of occlusion. Simulations revealed that the response characteristics of both classes of neurons were consistent with a model in which the responses to the occluded shape and the occluders are weighted separately and linearly combined. Overall, our results support the hypothesis that information about occluded and occluding stimuli are linearly separable and easily decodable from IT responses and that IT neurons encode a segmented representation of the visual scene.

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Visual Functions of Primate Area V4

Cited by 60 publications

References 148 publications

Curvature-processing domains in primate V4

Curvature-processing domains in primate V4

Feature representation under crowding in V1 and V4 neuronal populations

Encoding of Partially Occluded and Occluding Objects in Primate Inferior Temporal Cortex

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