Effects of d-amphetamine and prefrontal cortical cooling on delayed matching-to-sample behavior

The interaction was examined between d-amphetamine (s-A) and dysfunction induced by localized cooling of the dorsolateral prefrontal cortex. Saline or d-A(0.1,0.2 or 0.4 mg/kg) was administered to monkeys in two conditions; normal cortical temperature (no cooling -NC) and frontal cooling (FC). Errors, reaction time (RT), eye movements, and motor activity were recorded during performance of a delayed matching-to-sample task with intratrial delays of 1-32 sec. Although d-A and FC had little effect on percentage of correct responses at the shortest delay, each of the two treatments significantly decreased correct responses, at longer delays; drug and FC combined produced a significantly greater decrease than either treatment alone. Motor activity and eye movements were increased by either d-A or FC; the two treatments combined had an even greater effect. In the NC condition, two-choice RT was decreased by the drug; it was increased by drug-FC combinations. These findings indicate that d-A and FC potentiate each other in their behavioral effects.