Visually guided reaching and tactile discrimination performance in the monkey: the effects of removals of parietal cortex soon after birth.

Unilateral removals of parietal cortex were made soon after birth in 5 monkeys. The inferior parietal lobule was removed alone or together with the superior parietal lobule; the second somatosensory area (SII) was removed alone or together with posterior parietal surface cortex. Neurological changes were observed; and the animals were assessed quantitatively for their accuracy of reaching for visual targets and for their ability to discriminate between objects by palpation in the dark. Each hand was evaluated separately. Disorders of reaching (confined to the contralateral hand) were found to persist longer than in animals with comparable removals made at a later age; whereas the ability to make tactile discriminations was not more severely impaired after an early than a late ablation.