A cortical evoked potential that reflects the conditioned, positive incentive value of the stimulus. II. Drive motivation (hunger).

It was shown that the late negative wave evoked in squirrel monkey cortex by tone cues signalling the availability of reward was smaller when the animal did not respond to the cue and often disappeared if the animal ignored many cues in succession. It decreased in amplitude as a test session progressed, and the rate of this decrease increased if the rate of reinforcement was increased. In some animals the size of the evoked wave was smaller if the animal was not fasted before a test session. In some animals the average size of a significant positive correlation with the number of cues responded to and a negative correlation with the animal's average reaction time. It is concluded that the evoked wave is probably a reflection of the conditioned incentive value of the cue.