Effects of Ecstasy/Polydrug Use on Memory for Associative Information Running Head: Ecstasy and Associative Information

pattern was revealed. In a recognition phase, participants were presented with a single abstract pattern in the centre of the screen and asked to identify in which of the six boxes it had first appeared. The task consisted of two trials, where participants were required to learn six (Trial 1) and eight (Trial 2) pattern-location pairs. While there were no group differences on the majority of outcome measures, for number of errors, the group by trial interaction approached significance with posthoc tests confirming that ecstasy users made more errors than nonusers on the eight pair trial. Roberts et al. (2009) administered a face-number associative learning task in which participants learned to associate specific numbers with particular faces over a number of trials. Relative to cannabis-only controls and drug free persons, ecstasy users performed significantly worse overall averaged over all trials. During the performance of the task, fMRI revealed that ecstasy users displayed higher levels of activation in a number of brain regions including the left superior frontal gyrus, [BA (Brodman areas) 6 and 9], the middle frontal gyrus bilaterally, (BA 10 and 11) as well as bilateral temporal and occipital lobe structures. In addition, right hemisphere parietal lobe structures also exhibited higher levels of activation in ecstasy users. In contrast, ecstasy users had a number of regions exhibiting lower levels of activation (including the right anterior cingulate and the left posterior cingulate and parahippocampal gyrus). Both cannabis and ecstasy users exhibited lower levels of activation in the right medial frontal gyrus and left parahippocampalgyrus. It is possible that elevated activity levels in the prefrontal cortex are caused by this area taking over functions normally served by more posterior structures. Studies specifically examining word-pair associative learning in ecstasy/polydrug users have produced ambiguous results with apparent ecstasy-related effects confounded with other factors (Gouzoulis-Mayfrank et al. 2003) or due to other drugs (Montgomery et al. 2005a) or only apparent under more demanding conditions (Brown et al. 2010). In those studies where deficits have been observed ecstasy users’ failure to form paired associates as readily as nonusers might be attributable to a number of factors. For example, they may simply be unable to recall the response word. Alternatively, there might be a tendency for users to mismatch cues and responses by producing the associate of a different cue word. In this sense ecstasy users might be unable to maintain the original pair binding. This is in line with Kroll et al.’s (1996) theory that false memories are formed when we inappropriately recombine previously presented information to form episodes that have not occurred.