Specific Effects of Two Enantiomeres of N-ethyl-3,4-methylendioxyamphetamine (MDE) on Semantic Processing in fMRI

Abstract:
Abstract: A semantic processing task was used in order to study the neural correlates of the different psychotropic and neuropsychological effects of both the S- and R-enantiomere of MDE. After a baseline-measurement without drug the S- or the R-enantiomere were applicated in a randomized double-blind design. The cognitive task performed in fMRI was a semantic similarity judgement using word pairs which either were directly semantically related, indirectly semantically related or not semantically related. Color similarity judgements served as control conditions. Image processing and statistical analysis were carried out using SPM99b (Wellcome Institute of Neurology). Comparisons of the effects of the two enantiomeres against baseline revealed enhanced neural activity during application of the S-enantiomere that was regionally different from the neural activity during the R-enantiomere. S-enantiomere related activity was exclusively localized in right parietal and frontal regions. Comparing both drugs against each other increased neural activity was observed bilaterally in inferior frontal cortex for the S-enantiomere. These effects were paralleled by different effects of the enantiomeres on a behavioral semantic priming task. We conclude that there are specific neural correlates of the effects of the S- and R-enantiomeres of MDE on semantic processing. 1 Spitzer, M. et al. (1996). Cogn Brain Res, 4, 149-161