Ketamine-Induced Hallucinations

Psychopathology. 2015;48(6):376-85. doi: 10.1159/000438675. Epub 2015 Sep 12.


Background: Ketamine, the NMDA glutamate receptor antagonist drug, is increasingly employed as an experimental model of psychosis in healthy volunteers. At subanesthetic doses, it safely and reversibly causes delusion-like ideas, amotivation and perceptual disruptions reminiscent of the aberrant salience experiences that characterize first-episode psychosis. However, auditory verbal hallucinations, a hallmark symptom of schizophrenia, have not been reported consistently in healthy volunteers even at high doses of ketamine.

Sampling and methods: Here we present data from a set of healthy participants who received moderately dosed, placebo-controlled ketamine infusions in the reduced stimulation environment of the magnetic resonance imaging (MRI) scanner. We highlight the phenomenological experiences of 3 participants who experienced particularly vivid hallucinations.

Results: Participants in this series reported auditory verbal and musical hallucinations at a ketamine dose that does not induce auditory hallucination outside of the scanner.

Conclusions: We interpret the observation of ketamine-induced auditory verbal hallucinations in the context of the reduced perceptual environment of the MRI scanner and offer an explanation grounded in predictive coding models of perception and psychosis - the brain fills in expected perceptual inputs, and it does so more in situations of altered perceptual input. The altered perceptual input of the MRI scanner creates a mismatch between top-down perceptual expectations and the heightened bottom-up signals induced by ketamine. Such circumstances induce aberrant percepts, including musical and auditory verbal hallucinations. We suggest that these circumstances might represent a useful experimental model of auditory verbal hallucinations and highlight the impact of ambient sensory stimuli on psychopathology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Delusions / chemically induced
  • Dose-Response Relationship, Drug
  • Female
  • Frontal Lobe / drug effects*
  • Frontal Lobe / physiopathology*
  • Hallucinations / chemically induced*
  • Hallucinations / diagnosis
  • Humans
  • Ketamine / administration & dosage
  • Ketamine / adverse effects*
  • Magnetic Resonance Imaging
  • Male
  • Perception
  • Psychotic Disorders / drug therapy*
  • Psychotic Disorders / pathology
  • Young Adult


  • Ketamine