The effect of midazolam on implicit memory tests

Substantial empirical evidence exists suggesting that there are distinct forms of explicit and implicit memory. However, methodological problems have hampered attempts to identify the nature of the information processing underlying these forms of memory. These problems include the contamination of performance on implicit memory tests by explicit memory processes, as well as a host of difficulties inherent in correlational approaches that involve amnesiac subjects. In this paper we attempt to explore whether midazolam, a benzodiazepine used in surgical anesthesia, might be useful for studying implicit memory. Specifically, we attempt to determine whether midazolam produces selective effects on explicit, as opposed to implicit, memory. We focus on midazolam because of prior studies demonstrating that benzodiazepines do not affect implicit memory and because its rapid pharmacokinetics ensure that sedative effects are minimized when testing occurs at relatively short retention intervals. The results of an experiment using free recall, fragment completion and perceptual identification tests suggest that midazolam diminishes memory in implicit and explicit memory tests, although the diminution is proportionally larger in explicit memory. These results constrain the inferences that may be drawn when midazolam is used to explore implicit memory.