Direction of motion discrimination after early lesions of striate cortex (V1) of the macaque monkey

Previous studies have established that humans and monkeys with damage to st riate cortex are able to detect and localize bright targets within the resu ltant scotoma. Electrophysiological evidence in monkeys suggests that resid ual vision also might include sensitivity to direction of visual motion. We tested whether macaque monkeys with longstanding lesions of striate cortex (V1), sustained in infancy, could discriminate visual stimuli on the basis of direction of motion. Three monkeys with unilateral striate cortex lesio ns sustained in infancy were tested 2-5 years postlesion on a direction of motion discrimination task. Each monkey was trained to make saccadic eye mo vements to a field of moving dots or to withhold such eye movements, depend ing on the direction of motion in a coherent random dot display. With small er motion displays, monkeys were unable to detect or discriminate motion wi thin the scotoma, although they could discriminate moving from static stimu li. Yet, each monkey was able to discriminate direction of motion when the motion stimulus was larger, but still confined to the scotoma. The results demonstrate that the recovery after infant damage to striate cortex include s some sensitivity to direction of visual motion.