Effects of lorazepam upon recollective experience in recognition memory

The effects of lorazepam (2 mg) and placebo upon recognition memory with and without conscious recollection were assessed in a cross-over study with normal volunteers. When recognising a word from study lists presented before and 1, 3 and 5 h after drug administration, subjects were required to indicate whether they could consciously recollect the word's prior occurrence or recognised it on the basis of "knowing"; in the absence of conscious recollection. Lorazepam only impaired word recognition which was accompanied by conscious recollection, and further, the level of this impairment correlated significantly with each of three different indices of subjects' arousal at the time of presentation of each list. Recognition in the absence of conscious recollection was not impaired but somewhat heightened by lorazepam, and these effects did not significantly relate to any index of arousal. These findings are interpreted as providing further support for the notion that recognition entails two distinct components, one based on contextual and associative information and related to conscious recollection, the other possibly based on a "traceless" perceptual or semantic memory system and related to feelings of knowing in the absence of conscious recollection. Implications are drawn for a contextual-encoding/retrieval account of lorazepam-induced amnesia.