The effects of unilateral or bilateral removals of the second somatosensory cortex (area SII): a profound tactile disorder in monkeys.

Three groups of monkeys were studied; one with bilateral removals of the second somatosensory projection cortex (SII); another with similar unilateral removals; and an unoperated control group. Both lesion groups were significantly impaired on tasks of tactile learning and tactile retention. However, there were no differences between groups on the great majority of tasks of motor learning, nor on spatial alternation in the dark. The animals with unilateral removals were generally impaired whether using the hand contralateral to or ispilateral to the removal.