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Subtle effects of ketamine on memory when administered following stimulus presentation
David J LaPorte1, Teresa A Blaxton, Tamara Michaelidis
1Department of Psychology, Indiana University of Pennsylvania, Uhler Hall, Indiana, PA 15705-1068, USA. laporte@iup.edu
Psychopharmacology
|February 19, 2005
Summary
Ketamine did not affect word recall when given after learning, but it did reduce reminiscence. This suggests N-methyl-D-aspartate receptor antagonists impact memory consolidation.
Area of Science:
- Neuroscience
- Psychopharmacology
Background:
- N-methyl-D-aspartate (NMDA) receptor antagonists, like ketamine, are known to impair learning and memory.
- Previous human studies administered antagonists before learning, making it difficult to distinguish memory impairment from attention deficits.
Purpose of the Study:
- To investigate the effects of ketamine on verbal recall when administered *after* stimulus presentation.
- To differentiate direct effects on memory consolidation from secondary effects on attention or sensory processing.
Main Methods:
- A double-blind, placebo-controlled crossover study involving 24 healthy participants.
- Participants received ketamine (0.3 mg/kg) or placebo via injection.
- Verbal memory was tested before infusion, with delayed recall assessed 45 minutes post-infusion.
Main Results:
- Ketamine administration led to a significant increase in psychiatric symptoms.
- No significant differences were observed in immediate or delayed word recall between ketamine and placebo conditions.
- Reminiscence, the recall of previously unrecalled items, was significantly reduced after ketamine administration.
Conclusions:
- Ketamine's effects on memory are not solely due to attention deficits when administered post-stimulus.
- Findings indicate that NMDA receptor antagonism can impair specific aspects of memory consolidation, such as reminiscence.