College of Optometry Faculty Proceedings, Presentations, Posters, Speeches, Lectures, etc.

Title

Spatial summation properties of V2 neurons in macaque monkeys

Format

Poster

Conference Title

Society of Neuroscience Annual Meeting

Organization/Association/Group

Society of Neuroscience

Location

New Orleans, Louisiana / November 8-12, 2003

Publication Date / Copyright Date

10-1-2003

Abstract

Stimulation outside the classic receptive-field (CRF) of a primary visual cortical (V1) neuron results in contrast-dependent spatial interactions of neural signals (Sceniak et al, 1999; 2001; Cavanaugh et al, 2002). In this study we determined whether similar contrast dependent center-surround interactions exist in V2 neurons by performing area summation experiments both in V1 (n=54) and V2 (n=62) of anesthetized and paralyzed monkeys. The locations of the receptive fields were similar between the two areas and were within the central 6 degrees. Within animal comparisons of the surround effects between V1 and V2 revealed that the spatial summation properties of V2 neurons were generally similar to those in V1 units. Specifically, as in V1, the receptive fields of over 90% of V2 neuron consisted of an excitatory summation area (CRF) and a suppressive surround region. The magnitude of the surround effect ranged from complete (100%) suppression to no (0%) suppression both in V1 and V2. The overall strength of the surround suppression did not differ between V1 and V2 units when high contrast stimuli were used. As previously reported in V1, the diameters of the CRFs and the suppressive surrounds of V2 units were smaller when high contrast gratings (80%) were used compared to those measured with low contrast gratings (20%). Although the range of the CRF sizes were similar in both cortical areas, the average CRF of V2 units (2.31±0.14 degree) for high contrast gratings was much larger than that of V1 units (1.5±0.11 degree). The results suggest that the neuronal network underlying the spatial summation properties of V2 units are similar to that of V1 units.

Disciplines

Optometry

Keywords

visual cortex, extrastriate cortex, striate cortex, receptive field

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