Ketamine Disrupts Frontal and Hippocampal Contribution to Encoding and Retrieval of Episodic Memory: An fMRI Study
Cerebral Cortex November 10, 2004 G. Honey, R. Honey, C. O'Loughlin et al. 116 citations
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.