Fig. 1.

The effect of CS+ cue presentations and amphetamine microinjection (20 μg dose depicted) on responding for sucrose during extinction conditions. Presentation of the Pavlovian sucrose cue ordinarily triggered a moderate increase in responding on the sucrose-associated lever. Intra-accumbens amphetamine nearly tripled the incentive impact triggered by the CS+ sucrose cue, expressed by the increase in pressing elicited by the cue, but amphetamine had relatively little effect on pressing in the absence of the cue.