Effect of d-amphetamine on post-error slowing in healthy volunteers.

RATIONALE: Post-error slowing has long been considered a sign of healthy error detection and an important component of cognitive function. However, the neuropharmacological processes underlying post-error slowing are poorly understood. OBJECTIVES: This study investigated the effect of the dopamine agonist d-amphetamine on post-error slowing and secondarily, the potential mediator of drug-induced euphoria and potential moderators of personality and baseline task performance. METHODS: Healthy male and female participants (N = 110) completed four study sessions, at which d-amphetamine (placebo 5, 10, 20 mg) was administered under double-blind, counter-balanced conditions. At each session, participants completed subjective drug effect assessments and a working memory task (N-back) to measure post-error slowing. They completed the Multidimensional Personality Questionnaire (MPQ) during screening. RESULTS: Amphetamine (20 mg) reduced post-error slowing, consistent with a dampened behavioral reactivity to errors. This was not related to drug-induced euphoria. Although higher scores on MPQ constraint were related to less post-error slowing under placebo conditions, neither personality nor baseline cognitive performance moderated the effects of amphetamine on post-error slowing. CONCLUSIONS: The finding that amphetamine reduced post-error slowing supports the idea that dopamine plays a role in error stimulus processing. The finding is discussed in relation to an existing literature on the mechanisms and function of behavioral and electrophysiological indices of error sensitivity.