Effects of cortical lesions on somatosensory tasks

Abstract

Lesions were made in the subdivisions of the postcentral gyrus and in related cortical areas of monkeys. After the operation, the monkeys were trained on 6 tactual discrimination problems, and their performance was compared with those of a normal control group. Severe and apparently permanent damage to the ability to perform all tasks was observed after the postcentral lesions, but little or no effects were seen after the removal of the motor cortex or of the posterior parietal lobule. Destruction of area 3 of the postcentral gyrus had the most serious consequences, the monkeys with this lesion being unable to learn any but the easiest discriminations. Lesions of area 1 or of area 2 resulted in an inferior performance of tasks which required information mainly from cutaneous or deep receptors, respectively. The results of these behavioral studies support and extend the anatomical and physiologic data that demonstrate that the postcentral gyrus consists of a core area, which receives the heaviest thalamic projection and is crucial to a broad range of somatosensory functions, flanked by areas selectively responsive to stimulation of the cutaneous or the deep receptors. The fact that lesions of areas closely connected to the postcentral gyrus by corticocortical fibers do not impair somatosensory discriminations suggests that the necessary abilities are based mainly on the relation with the thalamus rather than on interareal cortical integration.