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INFLUENCE OF ATTENTION ON CENTER-SURROUND INTERACTIONS IN ALERT MONKEY V1.

MIT, Cambridge, Ctr. For Learning & Memory and Dept. of Brain & Cognitive Sci.

One of the remarkable properties of neurons in primary visual cortex (V1) is that their responses are modulated by the presence of stimuli outside the classical receptive field (CRF) only when a stimulus is placed within their CRF. A key issue is whether contextual modulation in V1 is a neural correlate of perception or merely a low-level competitive interaction of feed-forward inputs that vie for a neuron

s response. If contextual modulation aids perception, then this modulation should be influenced by the behavioral state of the animal, such as attention. Here we have investigated the spatial and temporal effects of the extra-classical surround on center responses and the influence of attentional state. Monkeys were trained to attend to a small peripheral spot while fixating on a centrally placed spot. They had to leave a bar as soon as the attention spot was extinguished while maintaining fixation in order to earn juice reward. After determining the cell

s receptive field and its preferred orientation, a center patch consisting of drifting sinusoidal gratings was placed within its CRF. A surround grating patch extending 5 degrees from the center, and of similar or orthogonal orientation to the CRF, was also presented. The attention spot was located within the cell

s CRF or in the opposite hemi-field. In cases where the attentional state was not manipulated, the iso-oriented surround suppressed center responses while the orthogonal surround either facilitated responses or had little influence. The suppressive effect of the surround was almost always preceded by an initial facilitation that lasted between 150-200 ms. These responses were compared with those when the monkey attended towards the CRF. Our preliminary results show that the influence of surround was delayed in time when attention was directed towards CRF. Thus center-surround interactions in V1 can be modulated by the attentional state of the animal.
Support Contributed By: NIH grant EY07023.

Citation:
J. Sharma, D.C. Lyon, M. Sur. INFLUENCE OF ATTENTION ON CENTER-SURROUND INTERACTIONS IN ALERT MONKEY V1. Program No. 484.6. 2003 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2003. Online.