An investigation of the effects of benzodiazepine receptor ligands and of scopolamine on conceptual priming

Scopolamine and lorazepam both produce anterograde impairments of explicit memory but only lorazepam impairs implicit memory as assessed by perceptual priming tasks. The main aim of the two experiments reported in this articl e was to determine the effects of these drugs on conceptual priming. Experi ment 1 compared the effects of lorazepam (1,2 mg PO) with scopolamine (0.3, 0.6 mg SC) and placebo in a study with 60 healthy volunteers. Experiment 2 compared the separate and combined effects of lorazepam (2 mg PO) and flum azenil (2 mg IV) with placebo in a study with 48 healthy volunteers. We fou nd that conceptual priming in category generation tasks was intact followin g lorazepam in both studies. This preservation of conceptual priming contra sted with lorazepam-induced impairments on explicit memory tasks. In conjun ction with previous findings, these results are interpreted as providing fu rther support for the notion that conceptual and perceptual priming are sub served by distinct memory systems, one based on the operations of semantic memory, the other possibly based on a perceptual representation system. Tha t lorazepam impairs perceptual but not conceptual priming suggests that the neurochemical substrates of the two kinds of priming are distinct.