Stimulus cancellation by macaques with unilateral frontal or parietal lesions.

Monkeys' spontaneous behaviors in cancelling a variety of visual and somatosensory stimuli were measured before, and acutely after, unilateral periarcuate (N = 16) and inferior parietal (n = 14) cortical removals. Postoperative behavior was analyzed for both severity of change from the preoperative baseline, and for the type of behavior (perceptual or premotor) affected by the lesion. Overall the two lesion groups could not be differentiated by severity or type of deficit. In two tasks, premotor deficits, manifest as extreme disuse of the hand contralateral to the lesion, were significantly worse in the parietal than the frontal group. In a third, the frontal group showed a greater perceptual deficit, manifest as marked preference for acting within ipsilesional space, than the parietal. In the three remaining tasks, premotor and perceptual deficits were equal in the two groups. These quantitative behavioral data suggest that deficits are more highly contingent upon task requirements than upon lesion sites. This in turn suggests that frontal and parietal association cortical fields each play multiple, and sometimes interchangeable, roles in the spatially directed attention and motor behavior of the monkey.