Abstract

Recent anatomical experiments in macaque monkeys have identified the presumed cortical pathway for motion processing. Using a combination of psychophysical, recording, and lesion techniques our laboratory has begun to investigate the types of motion processing that occur at each cortical level in this pathway. Our psychophysical experiments show that monkeys and humans have similar thresholds for perceiving shear motion and 2- and 3-D structures from motion. These experiments also show that the monkey and human nervous systems integrate motion information across both space and time to form neural representations of 3-D surfaces. Restricted ibotenic acid-induced cortical lesions to the middle temporal area (area MT) of macaque monkeys produced increased thresholds for the perception of both shear motion and structure from motion. These deficits were restricted to that part of the visual field that corresponded to the locus of the lesion within the retinotopic representation in area MT. The deficits appeared to be specific to motion perception since contrast sensitivity thresholds were not affected by the lesions. Interestingly the shear motion thresholds recovered in 3–4 days. This result suggests that either there has been a reorganization of the retinotopic map within regions of area MT that were not damaged or parallel motion pathways have been recruited or strengthened during the recovery period.

© 1987 Optical Society of America