ELECTRICAL STIMULATION OF FRONTAL CORTEX IN MONKEYS DURING LEARNING OF AN ALTERNATION TASK

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Abstract
Stimulating electrodes were implanted chronically over frontal cortex. Subjects were trained on an automatic alternation task throughout several testing sessions. Control monkeys had electrodes placed over occipital cortex and stimulation was applied during learning of visual discriminations. The stimulus was a square wave pulse, with settings of 1 millisec, 22 per sec., and strength of 60-90% of convulsive threshold. Results were (1) criterion on the alternation task was reached within normal limits of training trials; (2) during stimulation, scores of correct repsonses were depressed, but did not drop to chance level; (3) as performance on the task improved, stimulation became increasingly less effective in depressing learning scores; (4) after the task had been learned stimulation did not correct performance; (5) stimulation of occipital cortex had no effects on alternation, but interfered with learning of visual discriminations; (6) Stimulation of frontal cortex did not affect learning of visual discriminations.