EFFECT OF PREOCCIPITAL AND TEMPORAL DECORTICATION ON LEARNED VISUAL DISCRIMINATION IN MONKEYS

Abstract

Monkeys were trained to choose the correct one of 2 doors, one marked with upright and the other with inverted letter "F," to obtain food reward. If properly controlled, this represents a discrimination based on difference in pattern. When they had learned the discrimination, the monkeys were subjected to operation, i.e., aspiration of certain cortical areas, then retested to determine whether the discrimination habit had been retained. Extirpation of preoccipital cortex, roughly that designated as areas 18 and 19, abolished the discrimination if the left and right areas were removed in one operation. The discrimination could be relearned. If right and left sides were extirpated seriatim with training between operations, the habit was retained throughout, indicating a bilateral compensatory process initiated after unilateral operation. Subtotal temporal lobe decortication alone fails to affect the discrimination, but such operation on an animal already lacking parastriate areas abolishes the habit, which cannot be relearned. This is true of all animals lacking both parastriate and temporal cortex bilaterally, no matter what the order of operations. The authors conclude that the intact animal parastriate cortex is essentially concerned in leaving a discrimination, and temporal cortex, though not essentially involved in original learning, becomes essential in relearning after bilateral parastriate lesions.