Effect of an acute d-amphetamine administration on context information memory in healthy volunteers: evidence from a source memory task.

RATIONALE Previous research demonstrated a positive effect of d-amphetamine on long-term verbal memory. An improvement in memory for contextual information is proposed as a possible mechanism underlying the d-amphetamine facilitation effect. OBJECTIVES A double blind, placebo controlled experiment was used to examine the processes involved in episodic memory affected by an acute administration of d-amphetamine. We investigated whether positive effects of d-amphetamine on item memory could be extended to context information by using a source memory paradigm. METHODS In a within-subjects design with two sessions, two study lists were presented in each session and participants were required to make an old/new recognition decision (item memory) and a list discrimination judgement (source memory) after delays of 1 h, 1 day and 1 week. RESULTS Enhancement of item memory after d-amphetamine intake was observed on delayed tests only, confirming that amphetamine does not affect short-term memory or memory acquisition, but rather a process operating after initial encoding. Importantly, we found an enhancement in remembering the source of recognized items after d-amphetamine administration. CONCLUSION The present study suggests that an acute administration of d-amphetamine helps to bind different features of an item in memory, in turn leading to an increased ability to recollect both the item and its context.