Selective Tuning for Contrast in Macaque Area V4

Sani, Ilaria; Santandrea, Elisa; Golzar, Ashkan; Morrone, Maria Concetta; Chelazzi, Leonardo

doi:10.1523/jneurosci.3465-13.2013

Cited by 28 publications

(43 citation statements)

References 89 publications

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“…Indeed, while multiple physiological [38, 39] as well as psychophysical [21, 23, 24, 40] studies have linked changes in contrast detection and discrimination performance to response changes in a V1 population of neurons, activity in areas V2 and V3 has also been found to correlate with decisions in contrast detection tasks [41]. Even the majority of V4 neurons show monotonic sigmoidal contrast responses that can be characterised using parameter values largely similar to the ones we used [42], especially in case of short stimulus presentation durations [43]. …”

Section: Discussionmentioning

confidence: 99%

Apparent Motion Suppresses Responses in Early Visual Cortex: A Population Code Model

2016

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Two stimuli alternately presented at different locations can evoke a percept of a stimulus continuously moving between the two locations. The neural mechanism underlying this apparent motion (AM) is thought to be increased activation of primary visual cortex (V1) neurons tuned to locations along the AM path, although evidence remains inconclusive. AM masking, which refers to the reduced detectability of stimuli along the AM path, has been taken as evidence for AM-related V1 activation. AM-induced neural responses are thought to interfere with responses to physical stimuli along the path and as such impair the perception of these stimuli. However, AM masking can also be explained by predictive coding models, predicting that responses to stimuli presented on the AM path are suppressed when they match the spatio-temporal prediction of a stimulus moving along the path. In the present study, we find that AM has a distinct effect on the detection of target gratings, limiting the maximum performance at high contrast levels. This masking is strongest when the target orientation is identical to the orientation of the inducers. We developed a V1-like population code model of early visual processing, based on a standard contrast normalization model. We find that AM-related activation in early visual cortex is too small to either cause masking or to be perceived as motion. Our model instead predicts strong suppression of early sensory responses during AM, consistent with the theoretical framework of predictive coding.

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Section: Discussionmentioning

confidence: 99%

Apparent Motion Suppresses Responses in Early Visual Cortex: A Population Code Model

2016

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“…Neurons in most visual areas (except perhaps V4: Sani et al, 2013) respond poorly to low contrast stimuli. In these situations, the normalization operation is likely to be dominated by the constant term r of Eqs.…”

Section: Stimulus Propertiesmentioning

confidence: 99%

Contextual modulation and stimulus selectivity in extrastriate cortex

Krause

Pack

2014

Vision Research

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Contextual modulation is observed throughout the visual system, using techniques ranging from single-neuron recordings to behavioral experiments. Its role in generating feature selectivity within the retina and primary visual cortex has been extensively described in the literature. Here, we describe how similar computations can also elaborate feature selectivity in the extrastriate areas of both the dorsal and ventral streams of the primate visual system. We discuss recent work that makes use of normalization models to test specific roles for contextual modulation in visual cortex function. We suggest that contextual modulation renders neuronal populations more selective for naturalistic stimuli. Specifically, we discuss contextual modulation's role in processing optic flow in areas MT and MST and for representing naturally occurring curvature and contours in areas V4 and IT. We also describe how the circuitry that supports contextual modulation is robust to variations in overall input levels. Finally, we describe how this theory relates to other hypothesized roles for contextual modulation.

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“…This experimental situation is more analogous to natural 920 vision, where different aspects of a complex stimulus fall on the receptive fields of 921 different neurons. Using these stimuli, our results demonstrate that neuronal responses to 922 luminance and context are extremely heterogeneous (Figure 4; see also Bushnell et al, 923 2011;Sani et al, 2013), even as early as primary visual cortex. Furthermore, in response 924 to these stimuli, many individual units were not very sensitive to luminance (e.g.…”

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confidence: 51%

Neuronal population mechanisms of lightness perception

Ruff

Brainard

Cohen

2018

Preprint

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The way that humans and animals perceive the lightness of an object depends on its physical luminance as well as its surrounding context. While neuronal responses throughout the visual pathway are modulated by context, the relationship between neuronal responses and lightness perception is poorly understood. We searched for a neuronal mechanism of lightness by recording responses of neuronal populations in monkey primary visual cortex (V1) and area V4 to stimuli that produce a lightness illusion in humans, in which the lightness of a disk depends on the context in which it is embedded. We found that the way individual units encode the luminance (or equivalently for our stimuli, contrast) of the disk and its context is extremely heterogeneous. This motivated us to ask whether the population representation in either V1 or V4 satisfies three criteria: 1) disk luminance is represented with high fidelity, 2) the context surrounding the disk is also represented, and 3) the representations of disk luminance and context interact to create a representation of lightness that depends on these factors in a manner consistent with human psychophysical judgments of disk lightness. We found that populations of units in both V1 and V4 fulfill the first two criteria, but that we cannot conclude that the two types of information in either area interact in a manner that clearly predicts human psychophysical measurements: the interpretation of our population measurements depends on how subsequent areas read out lightness from the population responses.New & NoteworthyA core question in visual neuroscience is how the brain extracts stable representations of object properties from the retinal image. We searched for a neuronal mechanism of lightness perception by determining whether the responses of neuronal populations in primary visual cortex and area V4 could account for a lightness illusion measured using human psychophysics. Our results suggest that comparing psychophysics with population recordings will yield insight into neuronal mechanisms underlying a variety of perceptual phenomena.

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Selective Tuning for Contrast in Macaque Area V4

Cited by 28 publications

References 89 publications

Apparent Motion Suppresses Responses in Early Visual Cortex: A Population Code Model

Apparent Motion Suppresses Responses in Early Visual Cortex: A Population Code Model

Contextual modulation and stimulus selectivity in extrastriate cortex

Neuronal population mechanisms of lightness perception

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