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


Effects of Stimulus Contrasts on Long-range Signal Interactions in V1 and V2 Neurons of Macaque Monkeys



Conference Title

Society of Neuroscience Annual Meeting


Society of Neuroscience


San Diego, California / October 23-27. 2004

Publication Date / Copyright Date



Stimulation outside the classic receptive-field (CRF) of a V1 neuron is known to exert subthreshold inhibitory or excitatory influences over unit’s responses to stimuli confined to its CRF, depending on stimulus contrasts for CRF stimulation and the orientation of surround stimuli. However, it is not known whether V2 neurons show similar center/surround interactions or at what stimulus contrast for CRFs, the surround effects become excitatory from inhibitory. Using microelectrode recording methods in both V1 and V2 of normal adult monkeys, we examined the effects of high-contrast (80%) surround stimuli on CRF responses when center stimulus contrasts were varied for 2, 5, 10, 20, 50, 80 and 100%. The orientation of surround stimuli was either matched (iso-oriented) or orthogonal to CRF stimuli. Both in V1 and V2, iso-oriented surround stimuli exerted excitatory influences if CRF contrast was less than 30%, whereas orthogonal surround had inhibitory effects. The magnitude of these effects was greater in V2 than in V1. For CRF contrasts greater than 40%, iso-oriented surround stimuli exerted inhibitory effects while orthogonal surround gratings had little or no effects on CRF responses. These results suggest that although the neuronal network underlying the spatial summation properties of V2 neurons appears to be similar to that of V1 neurons, the surround effects are stronger and more extensive in V2 than in V1.




visual cortex, development, electrophysiology, receptive field

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