Contextual modulation in primary visual cortex

Investigated extra-receptive field contextual modulation (CM) in primary visual cortex (area V1) of 4 awake, behaving macaque monkeys. CM was studied using texture displays in which texture covering the receptive field (RF) was the same in all trials, but the perceptual context of this texture could vary depending on the configuration of extra-RF texture elements. Results show robust CM when disparity, color, luminance, and orientation cues variously defined a textured figure centered on the RF of V1 neurons. CM was found to have a spatial extent of 8-10 deg. diameter parafoveally. CM correlated with perceptual experience of both binocularly rivalrous texture displays and of displays with a simple example of surface occlusion. CM in V1 was found to have a characteristic latency of 80-100 msec after stimulus onset, potentially allowing feedback from extrastriate areas to underlie to this effect.