Reversal and nonreversal shifts under amphetamine

Abstract

Rats were trained in a Y maze on a two-choice simultaneous brightness discrimination with light as S+ and dark as S- (position irrelevant). Half of the animals were then switched to reversal, where the reinforcement contingencies of the original training were reversed, and the other half were switched to nonreversal, in which they learned a simultaneous right-left discrimination. Nonreversal was acquired faster than reversal in saline injected animals. The administration of 1 mg/kg d-amphetamine did not affect the acquisition of the initial brightness discrimination and of nonreversal. In contrast, the drug facilitated dramatically reversal learning. The results indicate that amphetamine enhances the attention to, or the associability of, the discriminative stimuli, leading to rapid learning to these stimuli under changed contingencies of reinforcement.

Facilitation of discrimination transfers under amphetamine: the relative control by S+ and S? and general transfer effects

“…Facilitated discrimination learning exhibited under amphetamine could stem from an enhancement of either of these processes or both. Our earlier experiments with reversal learning indicated that amphetamine did not affect the associative strengths of the discriminative stimuli, but rather enhanced the attention to, or the associability of, these stimuli (Weiner et al 1986 a, b;Weiner and Feldon 1986). The present results extend and clarify the effects of amphetamine on processes underlying discrimination learning.…”

“…This amphetamine-induced facilitation cannot be explained in terms of the establishment of approach and avoidance responses to specific stimuli, since the specific values of the discriminative stimuli were changed. However, for the same reason, this result cannot be attributed to enhanced associability of the specific discriminative stimuli, as was the case with reversal learning (Weiner and Feldon 1986). Thus, amphetamine-produced facilitation in the New S÷/ S-transfer reflects the effect of the drug on some other process involved in discrimination learning that is not stimulus specific.…”

“…position) common to both the initial and transfer problems (Mackintosh 1983). However, this possibility was ruled out by data from nonreversal learning (Weiner and Feldon 1986).…”

“…In a series of experiments, we tested the effects of I mg/ kg d-amphetamine on stimulus control using transfer from one discrimination to another (Weiner and Feldon 1986;Weiner et al 1986a, b). Animals were trained on a simultaneous brightness discrimination and then transferred either to nonreversal, in which the irrelevant (position) stimuli of the initial training became relevant, or to reversal, in which the original stimuli remained relevant but their reinforcement contingencies were reversed.…”

Contrasting effects of vasopressin, desglycinamide-vasopressin and amphetamine on a delayed matching to position task in rats

“…There is evidence from rodent studies to show that low doses (about 0.5-2.0 mg/kg) of the amphetamines can improve performance in certain reversal learning tasks, perhaps by enhancing attention or short term retrieval (Kulig and Calhoun 1972;Weiner and Feldon 1986), and that similar doses enhance retention of passive avoidance performance (Martinez et al 1980a), possibly by peripheral action (Martinez et al 1980a, b). In similar vein, Sahgal (1986) found that the drug (1-10 mg/kg) improved performance in a more complex avoidance task, and Robbins and Sahakian (1983) mention an unpublished study which suggested that an extremely low dose of AMP -0.05 mg/kg -had a small, barely significant, beneficial effect on accuracy in an auditory discrimination task.…”