The effects of a subpsychotic dose of ketamine on recognition and source memory for agency: implications for pharmacological modelling of core symptoms of schizophrenia

Neuropsychopharmacology. 2006 Feb;31(2):413-23. doi: 10.1038/sj.npp.1300846.

Abstract

Ketamine is increasingly used to model the cognitive deficits and symptoms of schizophrenia. We investigated the extent to which ketamine administration in healthy volunteers reproduces the deficits in episodic recognition memory and agency source monitoring reported in schizophrenia. Intravenous infusions of placebo or 100 ng/ml ketamine were administered to 12 healthy volunteers in a double-blind, placebo-controlled, randomized, within-subjects study. In response to presented words, the subject or experimenter performed a deep or shallow encoding task, providing a 2(drug) x 2(depth of processing) x 2(agency) factorial design. At test, subjects discriminated old/new words, and recalled the sources (task and agent). Data were analyzed using multinomial modelling to identify item recognition, source memory for agency and task, and guessing biases. Under ketamine, item recognition and cued recall of deeply encoded items were impaired, replicating previous findings. In contrast to schizophrenia, there was a reduced tendency to externalize agency source guessing biases under ketamine. While the recognition memory deficit observed with ketamine is consistent with previous work and with schizophrenia, the changes in source memory differ from those reported in schizophrenic patients. This difference may account for the pattern of psychopathology induced by ketamine.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Double-Blind Method
  • Excitatory Amino Acid Antagonists / administration & dosage*
  • Excitatory Amino Acid Antagonists / blood
  • Female
  • Humans
  • Ketamine / administration & dosage*
  • Ketamine / blood
  • Male
  • Memory Disorders / chemically induced*
  • Memory Disorders / physiopathology
  • Mental Recall / drug effects*
  • Models, Psychological
  • Neuropsychological Tests / statistics & numerical data
  • Recognition, Psychology / drug effects*
  • Schizophrenic Psychology*
  • Verbal Learning / drug effects

Substances

  • Excitatory Amino Acid Antagonists
  • Ketamine