RELATIONSHIP OF SLOW POTENTIAL CHANGES TO RESPONSE SPEED AND MOTIVATION IN MAN

Slow potential changes were recorded from the scalp of ten adult subjects during performance of a disjunctive reaction task. Tones separated by a constant 1.0 sec interval were employed for the conditional and imperative stimuli. The subject was instructed to execute or withhold a digital response, depending upon the frequency of the imperative stimulus. Motivational state was manipulated by two different sets of instructions. 1. 1. Contingent negative variations (CNVs) were obtained in all subjects under conditions of both high and low motivation. 2. 2. In a majority of subjects performing with closed eyes, potentials originating from the eyes were seen to contaminate activity recorded from the vertex. This problem was not encountered in subjects who had their eyes open and fixated. 3. 3. Within subjects, the fastest reaction times were preceded by CNVs of significantly larger amplitude than were the slowest responses. A comparable relationship was not found between subjects. 4. 4. Reaction times were shorter, and the negative evoked potential to the warning stimulus had a significantly greater amplitude when the subjects were in a state of high motivation than when they were urged to relax. Other potentials, including the CNV, did not show this difference between motivational conditions. 5. 5. Trials in which subjects were required to respond were followed by a broad positive wave of moderate amplitude, whereas trials in which they withheld a response were followed by a short positive wave of much greater amplitude. The height of both potentials was significantly correlated with mean reaction time across subjects. © 1969.