Faculty Opinions recommendation of Time course and time-distance relationships for surround suppression in macaque V1 neurons.

Finding a target among uniformly oriented non-targets is typically faster when this target is perpendicular, rather than parallel, to the non-targets. The V1 Saliency Hypothesis (V1SH), that neurons in the primary visual cortex (V1) signal saliency for exogenous attentional attraction, predicts exactly the opposite in a special case: each target or non-target comprises two equally sized disks displaced from each other by 1.2 disk diameters center-to-center along a line defining its orientation. A target has two white or two black disks. Each non-target has one white disk and one black disk, and thus, unlike the target, activates V1 neurons less when its orientation is parallel rather than perpendicular to the neurons’ preferred orientations. When the target is parallel, rather than perpendicular, to the uniformly oriented non-targets, the target’s evoked V1 response escapes V1’s iso-orientation surround suppression, making the target more salient. I present behavioral observations confirming this prediction.

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Strength of surround suppression is proportional to the time course of response magnitude in cat V1

Neuroscience Research ◽

10.1016/j.neures.2007.06.321 ◽

2007 ◽

Vol 58 ◽

pp. S55

Author(s):

Satoshi Shimegi

Keyword(s):

Time Course ◽

Response Magnitude ◽

Surround Suppression

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The time course of contrast masking reveals two distinct mechanisms of human surround suppression

Journal of Vision ◽

10.1167/6.6.808 ◽

2010 ◽

Vol 6 (6) ◽

pp. 808-808 ◽

Cited By ~ 1

Author(s):

Y. Petrov ◽

M. Carandini ◽

S. P. McKee

Keyword(s):

Time Course ◽

Surround Suppression

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The time course of different surround suppression mechanisms

10.1101/432773 ◽

2018 ◽

Author(s):

Michael-Paul Schallmo ◽

Alex M. Kale ◽

Scott O. Murray

Keyword(s):

Time Course ◽

Occipital Lobe ◽

Surround Suppression ◽

Neural Responses ◽

Response Component ◽

Low Level ◽

Response Characteristics ◽

Early Visual Cortex ◽

Suppression Mechanism ◽

Oriented Parallel

AbstractWhat we see depends on the spatial context in which it appears. Previous work has linked the reduction of perceived stimulus contrast in the presence of surrounding stimuli to the suppression of neural responses in early visual cortex. It has also been suggested that this surround suppression depends on at least two separable neural mechanisms, one ‘low-level’ and one ‘higher-level,’ which can be differentiated by their response characteristics. In a recent study, we found evidence consistent with these two suppression mechanisms using psychophysical measurements of perceived contrast. Here, we used EEG to demonstrate for the first time that neural responses in the human occipital lobe also show evidence of two separable suppression mechanisms. Eighteen adults (10 female and 8 male) each participated in a total of 3 experimental sessions, in which they viewed visual stimuli through a mirror stereoscope. The first session was used to definitively identify the C1 component, while the second and third comprised the main experiment. ERPs were measured in response to center gratings either with no surround, or with surrounding gratings oriented parallel or orthogonal, and presented either in the same eye (monoptic) or opposite eye (dichoptic). We found that the earliest ERP component (C1; ∼60 ms) was suppressed in the presence of surrounding stimuli, but that this suppression did not depend on surround configuration, suggesting a low-level suppression mechanism which is not tuned for relative orientation. A later response component (N1; ∼160 ms) showed stronger surround suppression for parallel and monoptic stimulus configurations, consistent with our earlier psychophysical results and a higher-level, binocular, orientation-tuned suppression mechanism. We conclude that these two surround suppression mechanisms have distinct response time courses in the human visual system, which can be differentiated using electrophysiology.

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Dynamics of Response to Perceptual Pop-Out Stimuli in Macaque V1

Journal of Neurophysiology ◽

10.1152/jn.00441.2007 ◽

2007 ◽

Vol 98 (6) ◽

pp. 3436-3449 ◽

Cited By ~ 11

Author(s):

Matthew A. Smith ◽

Ryan C. Kelly ◽

Tai Sing Lee

Keyword(s):

Visual Cortex ◽

Shape From Shading ◽

Feedback Signal ◽

Surround Suppression ◽

Contextual Modulation ◽

Modulation Response ◽

V1 Neurons ◽

Long Latency ◽

Specific Feedback ◽

Early Visual Cortex

Contextual modulation due to feature contrast between the receptive field and surrounding region has been reported for numerous stimuli in primary visual cortex. One type of this modulation, iso-orientation surround suppression, has been studied extensively. The degree to which surround suppression is related to other forms of contextual modulation remains unknown. We used shape-from-shading stimuli in a field of distractors to test the latency and magnitude of contextual modulation to a stimulus that cannot be distinguished with an orientation-selective mechanism. This stimulus configuration readily elicits perceptual pop-out in human observers and induces a long-latency contextual modulation response in neurons in macaque early visual cortex. We found that animals trained to detect the location of a pop-out stimulus were better at finding a sphere that appeared to be lit from below in the presence of distractors that were lit from above. Furthermore, neuronal responses were stronger and had shorter latency in the condition where behavioral performance was best. This asymmetry is compatible with earlier psychophysical findings in human observers. In the population of V1 neurons, the latency of the contextual modulation response is 145 ms on average (ranging from 70 to 230 ms). This is much longer than the latency for iso-orientation surround suppression, indicating that the underlying circuitry is distinct. Our results support the idea that a feature-specific feedback signal generates the pop-out responses we observe and suggest that V1 neurons actively participate in the computation of perceptual salience.

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The spatial extent over which neurons in macaque striate cortex pool visual signals

Visual Neuroscience ◽

10.1017/s0952523802194065 ◽

2002 ◽

Vol 19 (4) ◽

pp. 439-452 ◽

Cited By ~ 84

Author(s):

JONATHAN B. LEVITT ◽

JENNIFER S. LUND

Keyword(s):

Receptive Field ◽

Striate Cortex ◽

Macaque Monkey ◽

Visual Signals ◽

High Contrast ◽

Surround Suppression ◽

Low Contrast ◽

V1 Neurons ◽

Visual Inputs ◽

Recorded Activity

We recorded activity of single units in macaque monkey primary visual cortex (V1) to define the retinotopic extent of the visual inputs that drive or modulate V1 neuron responses in parafoveal and peripheral (calcarine) cortex. We used high-contrast drifting grating stimuli to define the extent of the area over which responses summate and the extent of the receptive-field surround. We found responses of most V1 cells to summate over 1 deg, with a suppressive surround typically twice that in diameter, though for some cells (even in parafoveal V1) surrounds exceeded 13 deg in diameter. Surprisingly, we found no significant laminar differences in these dimensions or in the strength of surround suppression. We found that surround suppression in most cells arises from both the ends and sides of the receptive field. Our measures indicate that the strongest modulatory input arises from regions immediately adjacent to the excitatory summation area. These physiological measures suggest that the high-contrast summation field of V1 neurons can be accounted for by the sum of lateral geniculate nucleus (LGN) inputs offered to the local cortical column, with monosynaptic lateral connections within area V1 adding the larger dimensions of the low-contrast summation field and the near surround. Neither of these inputs suffice to explain the largest surrounds, which most likely derive from feedback from extrastriate visual areas.

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Visual Spatial Characterization of Macaque V1 Neurons

Journal of Neurophysiology ◽

10.1152/jn.2001.85.5.1873 ◽

2001 ◽

Vol 85 (5) ◽

pp. 1873-1887 ◽

Cited By ~ 167

Author(s):

Michael P. Sceniak ◽

Michael J. Hawken ◽

Robert Shapley

Keyword(s):

Spatial Organization ◽

Spatial Summation ◽

Surround Suppression ◽

Visual Responses ◽

V1 Neurons ◽

Spatial Characterization ◽

Difference Of Gaussians ◽

Visual Spatial ◽

Dog Model

This study characterizes the spatial organization of excitation and inhibition that influences the visual responses of neurons in macaque monkey's primary visual cortex (V1). To understand the spatial extent of excitatory and inhibitory influences on V1 neurons, we performed area-summation experiments with suprathreshold contrast stimulation. The extent of spatial summation and the magnitude of surround suppression were estimated quantitatively by analyzing the spatial summation experiments with a difference of Gaussians (DOG) model. The average extent of spatial summation is approximately the same across layers except for layer 6 cells, which tend to sum more extensively than cells in the other layers. On average, the extent of length and width summation is approximately equal. Across the population, surround suppression is greatest in layer 4B and weakest in layer 6. Estimates of summation and suppression are compared for the DOG (subtractive) model and a normalization (divisive) model. The two models yield quantitatively similar estimates of the extent of excitation and inhibition. However, the normalization (divisive) model predicts weaker surround strength than the DOG model.

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