EFFECTS OF SMALL LESIONS IN SENSORY CORTEX IN TRAINED MONKEYS

Abstract

Small lesions were made in the hand region of the classical sensory cortex (areas 3,1 and 2) of trained Macaca nemestrina monkeys. The consequent impairment was measured and stated in quantitative terms by means of tests for motor power, dexterity and the ability to make tactile discriminations. Post-operative recovery was also recorded. The results obtained are compared and contrasted with similar lesions previously made in the motor cortex (area 4) of other monkeys. Sensory cortex lesions did not cause inability to make movements, but did cause loss of tactile sensation, marked impairment of motor power and dexterity and, in some cases, unawareness of the movements made and the arrest of a limb in a bizarre position. Histological examination of the brains by the Marchi method was made in order to correlate anatomical data with functional loss. These studies showed that there was a most intimate connection of areas 3, 1 and 2 with area 4, and also that these 4 cortical areas form a unit linked with the thalamus and spinal cord, but sending few fibers into areas more anterior and posterior.