Benzodiazepines and semantic memory: effects of lorazepam on the Moses illusion

When asked "How many animals of each kind did Moses take on the ark?", people fail to notice the distortion introduced by the impostor "Moses" and respond "two". It has been argued that the effect must be due to the existence of a partial-match process. In most situations, the form of a question is not likely to closely match the memory representation it queries. Thus, for the partial match hypothesis people ignore some semantic distortions. In the same vein, it has been shown that the benzodiazepine lorazepam drug induces some impairments of semantic memory as participants under lorazepam provide more incorrect recalls than placebo do with general information questions. The aim of this study was to investigate the effects of the benzodiazepine lorazepam on the Moses illusion paradigm. The effects of lorazepam (0.038 mg/kg) and of a placebo were investigated in 28 healthy volunteers. Twenty-two illusory questions were presented along with 72 normal general information questions. Lorazepam impaired the ability to detect the Moses illusion. Moreover, lorazepam participants appeared less biased to consider a question distorted than placebo participants. The temporary and reversible semantic memory impairments experienced by participants when falling into the Moses illusion are more frequent under lorazepam. The amnesic drug lorazepam may impair semantic processing as well as the strategic control of memory.