Effects of prior experience on differential learning under amphetamine.

Differential learning of operant behavior under non-drug and amphetamine states was explained with a "drug-behavior-reinforcement interaction" process. When a drug affects the relationship between ongoing behavior and existing reinforcement contingencies, the sets of behavioral patterns subjected to the process of reinforcement or non-reinforcement under a drug may differ from the patterns under non-drug conditions. If, following sufficient training, the drug conditions are then changed, persistence of these behavioral patterns may result in a difference from those patterns produced if acquisition occurs solely under non-drug conditions. To investigate this process, groups of rats were given varying amounts of non-drug acquisition training on a response-duration differentiation task before being given extended training under 0.75 mg/kg d-amphetamine. All groups were then tested under non-drug conditions. Amphetamine significantly enhanced performance, and this enhancement transferred to subsequent non-drug conditions. However, if non-drug training occurred before drug training, this enhancement was greatly attenuated. Furthermore, only those behavioral components under which amphetamine led to an increase in reinforcement rate showed enhancement in the non-drug state. The results, which supported the present position, were discussed in relation to a "stimulus generalization decrement" explanation of differential learning under amphetamine.