A cortical evoked potential that reflects the conditioned, positive incentive value of the stimulus. I. The evoked potential.

As squirrel monkeys learned that a tone cue signalled the availability of a food reward there appeared in pre- and post-central cortex a surface negative waveform in response to the cue. This waveform disappeared, concomitantly with the animal's behavioral response, during extinction and pseudoconditioning. It was independent of changes in cue intensity sufficient to markedly alter earlier components of evoked activity and it disappeared when evoked activity was averaged with the behavioral response, rather than the cue, as reference point. It was concluded that this evoked potential reflects cortical activity somewhere in the stimulus-response sequence between the recognition of the cue and the decision to act.