Exploring the Effects of Diazepam and Lorazepam

Aims : * exploring lorazepam (0.038 mg/kg) effects, after a single oral intake, in healthy volunteers, on the neural correlates of encoding and retrieval of information during a word-stem completion task (implicit memory), using fMRI * comparing lorazepam effects to diazepam (0.3 mg/kg)effects * exploring benzodiazepines effects, after a single oral intake, on the neural correlates of successful encoding of information within explicit memory using fMRI Hypothesis : * both diazepam and lorazepam will impair explicit memory performance, but lorazepam only will impair perceptual priming * lorazepam and diazepam will modify the normal correlates of information encoding within explicit memory * lorazepam only will alter the neural correlates of perceptual priming