The effects of scopolamine, an anticholinergic drug, of trimipramine, a tricyclic antidepressant with both anticholinergic and sedative properties, of diazepam and a placebo, on explicit memory and repetition priming were assessed using a free-recall task and a word-stem completion task. Forty-eight healthy volunteers took part in this double-blind study. Diazepam provoked a dissociation between free recall, which was profoundly impaired, and word completion, which was spared. No significant changes in memory performances were observed in the scopolamine group; however, a significant correlation between explicit and implicit memory performances was observed in this group. At the low dose used, the effects of trimipramine on memory were mild. The results suggest that the cholinergic system is involved in the priming effect.
The effects of 0.2 mg/kg orally administered diazepam and of a placebo on explicit memory, implicit and knowledge memory were assessed using a free recall task, a word-stem completion task and two category-generation tasks. Twenty four healthy volunteers took part in this double-blind study. Diazepam impaired explicit but not implicit memory. The drug also spared knowledge memory. Explicit memory was linked with the diazepam-induced sedation and with the self-rated affective load of to-be remembered words, but implicit memory was not. The diazepam-induced dissociation between explicit and implicit memory supports the notion of two distinct forms of memory and reproduced the dissociation observed in organic amnesia.
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