STIMULUS COMPETITION IN ATTENTION: A NEURAL MODEL OF VISUAL CORTEX AREA V4

When a monkey is presented simultaneously two stimuli in the receptive field of a neuron in the visual cortex area V4, the neuron firing rate response is intermediate between the neuron response when both stimuli are presented alone. This phenomenon is called stimulus competition. To study its basic underlying neural mechanisms, we calculate the neuron firing rate response to different stimulus configurations. We find that stimulus competition can arise from the neuron's response properties alone, but only for a limited set of stimulus pair parameters. Furthermore, network properties may be important in modifying the inputs so that competition may occur for much wider sets of stimulus pairs.

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Population receptive field tuning properties of visual cortex during childhood

10.1101/213108 ◽

2017 ◽

Cited By ~ 2

Author(s):

T. M. Dekker ◽

D.S. Schwarzkopf ◽

B. de Haas ◽

M. Nardini ◽

M.I. Sereno

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Spatial Information ◽

Neural Mechanisms ◽

Neuronal Populations ◽

Spatial Tuning ◽

Age Related ◽

Visuospatial Perception ◽

Cortical Magnification ◽

Age Related Changes

AbstractImprovements in visuospatial perception such as contrast sensitivity and Vernier acuity continue until late in childhood, but the neural mechanisms driving these age-related changes are currently unclear. One contributing factor could be the protracted development of spatial tuning of neuronal populations across the visual cortex. Here we tested this possibility using population receptive field (pRF) mapping (Dumoulin and Wandell, 2008) in 6-to 12-year-old children and adults. We fitted pRF models to BOLD signals measured in areas V1-V4 and V3a during fMRI whilst participants watched wedge and ring stimuli traversing the visual field. Cortical magnification and the width of pRF tuning functions changed with viewing eccentricity in all participants. However, there were no age-related changes in pRF size, shape, cortical magnification, or map consistency across any of the visual areas measured. These results suggest that visuospatial perception in late childhood beyond age 6 years is not substantially limited by low-level spatial tuning properties of neuronal populations in visual cortex. Instead, performance improvements in this period may reflect more efficient use of the spatial information available in the visual system when forming perceptual judgments. These findings are an important step towards disentangling which neural mechanisms contribute to the eventual emergence of mature spatial vision, and for understanding the processes that determine the scope for visual plasticity at different stages of life.

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Responses of Primate Visual Cortical V4 Neurons to Simultaneously Presented Stimuli

Journal of Neurophysiology ◽

10.1152/jn.2002.88.3.1128 ◽

2002 ◽

Vol 88 (3) ◽

pp. 1128-1135 ◽

Cited By ~ 44

Author(s):

Timothy J. Gawne ◽

Julie M. Martin

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Firing Rate ◽

Cortical Neurons ◽

Clear Relationship ◽

Substantial Fraction ◽

Receptive Field Properties ◽

Direct Support ◽

V4 Neurons ◽

Visual Cortical

We report here results from 45 primate V4 visual cortical neurons to the preattentive presentations of seven different patterns located in two separate areas of the same receptive field and to combinations of the patterns in the two locations. For many neurons, we could not determine any clear relationship for the responses to two simultaneous stimuli. However, for a substantial fraction of the neurons we found that the firing rate was well modeled as the maximum firing rate of each stimulus presented separately. It has previously been proposed that taking the maximum of the inputs (“MAX” operator) could be a useful operation for neurons in visual cortex, although there has until now been little direct physiological evidence for this hypothesis. Our results here provide direct support for the hypothesis that the MAX operator plays a significant (although certainly not exclusive) role in generating the receptive field properties of visual cortical neurons.

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Modulation of Sensory Suppression: Implications for Receptive Field Sizes in the Human Visual Cortex

Journal of Neurophysiology ◽

10.1152/jn.2001.86.3.1398 ◽

2001 ◽

Vol 86 (3) ◽

pp. 1398-1411 ◽

Cited By ~ 179

Author(s):

Sabine Kastner ◽

Peter De Weerd ◽

Mark A. Pinsk ◽

M. Idette Elizondo ◽

Robert Desimone ◽

...

Keyword(s):

Visual Cortex ◽

Visual Field ◽

Receptive Field ◽

Neural Representation ◽

Lower Visual Field ◽

Human Visual Cortex ◽

Area V4 ◽

Upper Visual Field ◽

Neurophysiological Studies ◽

Extrastriate Areas

Neurophysiological studies in monkeys show that when multiple visual stimuli appear simultaneously in the visual field, they are not processed independently, but rather interact in a mutually suppressive way. This suggests that multiple stimuli compete for neural representation. Consistent with this notion, we have previously found in humans that functional magnetic resonance imaging (fMRI) signals in V1 and ventral extrastriate areas V2, V4, and TEO are smaller for simultaneously presented (i.e., competing) stimuli than for the same stimuli presented sequentially (i.e., not competing). Here we report that suppressive interactions between stimuli are also present in dorsal extrastriate areas V3A and MT, and we compare these interactions to those in areas V1 through TEO. To exclude the possibility that the differences in responses to simultaneously and sequentially presented stimuli were due to differences in the number of transient onsets, we tested for suppressive interactions in area V4, in an experiment that held constant the number of transient onsets. We found that the fMRI response to a stimulus in the upper visual field was suppressed by the presence of nearby stimuli in the lower visual field. Further, we excluded the possibility that the greater fMRI responses to sequential compared with simultaneous presentations were due to exogeneous attentional cueing by having our subjects count T's or L's at fixation, an attentionally demanding task. Behavioral testing demonstrated that neither condition interfered with performance of the T/L task. Our previous findings suggested that suppressive interactions among nearby stimuli in areas V1 through TEO were scaled to the receptive field (RF) sizes of neurons in those areas. Here we tested this idea by parametrically varying the spatial separation among stimuli in the display. Display sizes ranged from 2 × 2° to 7 × 7° and were centered at 5.5° eccentricity. Based on the effects of display size on the magnitude of suppressive interactions, we estimated that RF sizes at an eccentricity of 5.5° were <2° in V1, 2–4° in V2, 4–6° in V4, larger than 7° (but still confined to a quadrant) in TEO, and larger than 6° (confined to a quadrant) in V3A. These estimates of RF sizes in human visual cortex are strikingly similar to those measured in physiological mapping studies in the homologous visual areas in monkeys.

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A distinct population of heterogeneously color-tuned neurons in macaque visual cortex

Science Advances ◽

10.1126/sciadv.abc5837 ◽

2021 ◽

Vol 7 (8) ◽

pp. eabc5837

Author(s):

Sunny Nigam ◽

Sorin Pojoga ◽

Valentin Dragoi

Keyword(s):

Visual Cortex ◽

Natural Scenes ◽

Natural Environments ◽

Social Signals ◽

Distinct Population ◽

Area V4 ◽

Cortex Area ◽

Close Proximity ◽

Color Signals ◽

High Degree

Color is a key feature of natural environments that higher mammals routinely use to detect food, avoid predators, and interpret social signals. The distribution of color signals in natural scenes is widely variable, ranging from uniform patches to highly nonuniform regions in which different colors lie in close proximity. Whether individual neurons are tuned to this high degree of variability of color signals is unknown. Here, we identified a distinct population of cells in macaque visual cortex (area V4) that have a heterogeneous receptive field (RF) structure in which individual subfields are tuned to different colors even though the full RF is only weakly tuned. This spatial heterogeneity in color tuning indicates a higher degree of complexity of color-encoding mechanisms in visual cortex than previously believed to efficiently extract chromatic information from the environment.

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Neural Mechanisms of Spatial Selective Attention in Areas V1, V2, and V4 of Macaque Visual Cortex

Journal of Neurophysiology ◽

10.1152/jn.1997.77.1.24 ◽

1997 ◽

Vol 77 (1) ◽

pp. 24-42 ◽

Cited By ~ 973

Author(s):

Steven J. Luck ◽

Leonardo Chelazzi ◽

Steven A. Hillyard ◽

Robert Desimone

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Selective Attention ◽

Receptive Fields ◽

Simultaneous Presentation ◽

Neural Mechanisms ◽

Spontaneous Firing ◽

Firing Rates ◽

Behavioral Paradigm ◽

Sensory Responses

Luck, Steven J., Leonardo Chelazzi, Steven A. Hillyard, and Robert Desimone. Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex. J. Neurophysiol. 77: 24–42, 1997. Many neurons in extrastriate visual cortex have large receptive fields, and this may lead to significant computational problems whenever multiple stimuli fall within a single field. Previous studies have suggested that when multiple stimuli fall within a cell's receptive field, they compete for the cell's response in a manner that can be biased in favor of attended stimuli. In the present study we examined this role of attention in areas V1, V2, and V4 of macaque monkeys with the use of a behavioral paradigm in which attention was directed to one of two stimulus locations. When two stimuli were presented simultaneously inside the cell's receptive field (which could be accomplished only in areas V2 and V4), we found that the cell's response was strongly influenced by which of the two stimuli was attended. The size of this attention effect was reduced when the attended and ignored stimuli were presented sequentially rather than simultaneously. In addition, the effects became very weak and inconsistent in these areas when only one of the two stimuli was located inside the receptive field. Attention thus modulated sensory responses primarily when two or more simultaneous stimuli competed for access to a neuron's receptive field. As in areas V2 and V4, attention did not modulate sensory responses in area V1 when only a single stimulus was inside the receptive field. In addition, the small receptive fields in this area precluded the simultaneous presentation of attended and ignored stimuli inside the receptive field, making it impossible to determine whether attention effects would be observed under the conditions that led to consistent attention effects in areas V2 and V4. Spontaneous firing rates in areas V2 and V4 were found to be 30–40% higher when attention was directed inside rather than outside the receptive field, even when no stimulus was present in the receptive field. Spontaneous firing rates also varied according to the particular location within the receptive field that was attended. These shifts in spontaneous activity may reflect a top-down signal that biases responses in favor of stimuli at the attended location.

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Faculty Opinions recommendation of Receptive field structure varies with layer in the primary visual cortex.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1024414.287911 ◽

2005 ◽

Author(s):

Matteo Carandini

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Primary Visual Cortex ◽

Field Structure

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Faculty Opinions recommendation of Population receptive field estimates in human visual cortex.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1095861.564007 ◽

2008 ◽

Author(s):

Josh Trachtenberg

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Human Visual Cortex

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Superimposed gratings induce diverse response patterns of gamma oscillations in primary visual cortex

Scientific Reports ◽

10.1038/s41598-021-83923-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bin Wang ◽

Chuanliang Han ◽

Tian Wang ◽

Weifeng Dai ◽

Yang Li ◽

...

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Field Potential ◽

Gamma Oscillations ◽

Neural Mechanisms ◽

Model Parameters ◽

Response Patterns ◽

Region Difference ◽

High Gamma ◽

Spiking Activity

AbstractStimulus-dependence of gamma oscillations (GAMMA, 30–90 Hz) has not been fully understood, but it is important for revealing neural mechanisms and functions of GAMMA. Here, we recorded spiking activity (MUA) and the local field potential (LFP), driven by a variety of plaids (generated by two superimposed gratings orthogonal to each other and with different contrast combinations), in the primary visual cortex of anesthetized cats. We found two distinct narrow-band GAMMAs in the LFPs and a variety of response patterns to plaids. Similar to MUA, most response patterns showed that the second grating suppressed GAMMAs driven by the first one. However, there is only a weak site-by-site correlation between cross-orientation interactions in GAMMAs and those in MUAs. We developed a normalization model that could unify the response patterns of both GAMMAs and MUAs. Interestingly, compared with MUAs, the GAMMAs demonstrated a wider range of model parameters and more diverse response patterns to plaids. Further analysis revealed that normalization parameters for high GAMMA, but not those for low GAMMA, were significantly correlated with the discrepancy of spatial frequency between stimulus and sites’ preferences. Consistent with these findings, normalization parameters and diversity of high GAMMA exhibited a clear transition trend and region difference between area 17 to 18. Our results show that GAMMAs are also regulated in the form of normalization, but that the neural mechanisms for these normalizations might differ from those of spiking activity. Normalizations in different brain signals could be due to interactions of excitation and inhibitions at multiple stages in the visual system.

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