Dopamine and the elements of incentive learning explains how, in lever pressing for food tasks, incentive learning produces a gradient of attractiveness of environment stimuli: during magazine training, food activates dopaminergic neurons and the click and food cup become conditioned incentive stimuli, acquiring the ability to elicit approach and other responses; during lever-press training, the click activates dopaminergic neurons and the lever and lever-related stimuli become conditioned incentive stimuli. In conditioned place preference, amphetamine enhances dopaminergic neurotransmission and stimuli paired with amphetamine become conditioned incentive stimuli. In conditioned activity experiments, test-box stimuli paired with a dopamine-enhancer, e.g., cocaine, produce greater activity revealing incentive learning. In conditioned avoidance, the offset of an aversive warning stimulus putatively activates dopaminergic neurons leading safety-related stimuli to become conditioned incentive stimuli. If trained animals are treated with a dopamine receptor blocker, the initially intact ability of conditioned incentive stimuli to control responding declines over trials.
Age-dependent differences in the strength and persistence of psychostimulant-induced conditioned activity in rats
