Visuomotor deficits and fast recovery after area V6A lesion in monkeys.

In order to study the involvement of area V6A in visually guided behavior, restricted lesions to the anterior bank of the parieto-occipital sulcus (POs) were made in two adult Cercopithecus aethiops monkeys, trained in visuomotor tests. Beside the known clinical signs of parietal deficit (abnormal posture of the arm contralateral to the most recent lesion and reluctance to use it), misreaching was evident soon after surgery and disappeared quickly. Uncertainties in a landmark test and prolonged response times to the pressing of light-buttons lasted for a few weeks and 1 month, respectively. As suggested by previous anatomical and physiological data, these findings confirm the role of the POs region in the execution of reaching movements. Moreover, they also demonstrate that following lesion, locally networked areas can rapidly adjust in order to re-establish pre-lesional behavior. These adjustments take place well before that any anatomical changes may occur.