ACTIVITY CHANGES IN EARLY VISUAL-CORTEX REFLECT MONKEYS PERCEPTS DURING BINOCULAR-RIVALRY

WHEN the two eyes view dissimilar images, we experience binocular riva lry, in which one eye's view dominates for several seconds and is then replaced by that of the other eye(1,2). What causes these perceptual changes in the absence of any change in the stimulus? We showed previo usly that some neurons in monkey cortical area MT show changes in acti vity during motion rivalry that reflect the perceived direction of mot ion(3). To determine whether perception-related modulation of activity occurs in other visual cortical areas, we recorded from individual ne urons in V1, V2 and V4 while monkeys reported the perceived orientatio n of rival gratings of two orthogonal orientations. Many cells, partic ularly in V4, showed patterns of activity that correlated with the per ceptual dominance and suppression of one stimulus. The majority were o rientation-selective and could be driven equally well from either eye. It has been previously suggested that binocular rivalry involves reci procal inhibition between monocular neurons within V1 (for example, se e ref, 4), but our results do not support this view; rather, we propos e that binocular rivalry arises through interactions between binocular neurons at several levels in the visual pathways, and that similar me chanisms may underlie other multistable perceptual states that occur w hen viewing ambiguous images.