Effects of d-amphetamine on the performance of rats in an animal analogue of the A-X Continuous Performance Test

Schizophrenia patients subjected to the A-X Continuous Performance Test (A- X CPT) show cognitive deficits that are thought to reflect impaired represe ntation and maintenance of context information, An issue deserving attentio n is to what extent the acute amphetamine model of schizophrenia also model s these cognitive deficits. The present experiment examined the effect of a cute d-amphetamine (AMP) on the performance of rats in an animal analogue o f the A-X CPT, Subjects first learned to solve an A --> X +, B --> X -, A - -> Y- discrimination task, with A and B representing visual features; X and Y designating auditory target stimuli; --> signifying a serial presentatio n; and + and - referring to food reinforcement and nonreinforcement, respec tively. Frequency of food-magazine visits was the dependent measure. After mastering the discrimination, rats received test trials under either saline or 0.5 mg/kg AMP (s.c.). At test, the interval between feature and target presentation was varied; reinforcement contingencies were maintained. AMP s ignificantly impaired performance on the A --> X +/ B --> X - discriminatio n by increasing the response level on 13 --> X - trials. AMP did not signif icantly affect performance on the A --> X +/ A --> Y - discrimination. Howe ver, AMP also increased magazine responding in the absence of the presentat ion of features and targets. A parsimonious conclusion based on these preli minary results is that acute AMP does not affect processing of context info rmation provided by the visual features in this procedure. It rather has a more nonspecific response-enhancing effect, especially with respect to stim uli associated with the delivery of food.