Alteration of response patterning by d-amphetamine on repeated acquisition in rats.

The acute effects of d-amphetamine on response patterning in a repeated acquisition baseline were investigated with rats. Each session the animals acquired a different four-member response sequence on three levers. Each sequence (trial) completion produced a food pellet. Errors produced a brief timeout that was reset by responses made during the timeout. Acute doses of d-amphetamine (0.5-4.0 mg/kg) and saline were administered 30 min presession. The response patterns analyzed were perseverative responses to a single lever (runs), and a response to each lever in either a left-to-right or right-to-left direction (traverses). The trial position, frequency, and lever location of error and timeout responses that occurred in the context of runs and traverses were studied. In contrast to control sessions, higher doses of d-amphetamine produced increases in the number of error and timeout responses emitted. The majority of these responses occurred as runs; traverse responding did not exceed control levels. Furthermore, the run error and timeout responding tended to occur early in the session and on a single response lever. The results are consistent with the view that d-amphetamine disrupts stimulus control and produces perseverative responding which may account for previous reports of disruption in repeated acquisition tasks following d-amphetamine administration.