Ketamine, a drug that blocks NMDA receptors, impairs episodic memory. Using fMRI, brain activity was measured in healthy volunteers during memory encoding and retrieval under two intravenous doses of ketamine in a double-blind, placebo-controlled, randomized, within-subjects design. Encoding and retrieval were separated across two study-test cycles to isolate drug effects on each process. Results suggest that ketamine increases left frontal activation when elaborative semantic processing is needed during encoding, and successful encoding on the drug relies on additional incidental non-verbal processing. At retrieval, ketamine appears to impair access to contextual features of studied items. Even when behavior appears normal, ketamine alters recruitment of key brain regions for episodic memory.
A small pilot study tested whether a low dose of ketamine could increase hypnotizability in healthy volunteers who initially scored low on the Stanford Clinical Hypnotizability Scale. Ketamine, used clinically as an anesthetic and for depression, can produce dissociation and detachment similar to hypnotic states. Participants' subjective dissociation ratings and hypnotizability scores both moved in the predicted direction, but the results were not definitive. The findings suggest that further research is warranted to explore ketamine's potential to enhance hypnotizability.