Subanaesthetic ketamine and altered states of consciousness in humans
Phillip E. Vlisides, Tarik Bel‐bahar, Amanda Nelson, K. Chilton, Ezra E. Smith, Ellen Janke, Vijay Tarnal, Paul Picton, Richard E. Harris, George A. Mashour
British Journal of Anaesthesia April 13, 2018 DOI: 10.1016/j.bja.2018.03.011 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study Peer reviewed |
|---|---|
| Sample size | 15 |
| Population | Human volunteers |
| Intervention | Ketamine infusion |
| Dose | 0.5 mg kg-1 over 40 min |
| Duration | Before, during, and after 40-minute infusion |
| Topics | Ketamine Altered states of consciousness Esketamine |
| Keywords | Altered state Consciousness Cognitive science |
| Citations | 117 |
| Key findings | Ketamine-induced altered states of consciousness are accompanied by reduced alpha power in the precuneus and temporal-parietal junction. |
Abstract
BackgroundDespite its designation as a 'dissociative anaesthetic,' the dissociative and psychoactive effects of ketamine remain incompletely understood. The goal of this study was to characterise the subjective experiences and accompanying EEG changes with subanaesthetic doses of ketamine.MethodsHigh-density EEG was recorded in 15 human volunteers before, during, and after subanaesthetic ketamine infusion (0.5 mg kg-1 over 40 min), with self-reported measures of altered states of consciousness obtained after ketamine exposure. Sensor- and source-level EEG changes were analysed with a focus on spectral power and regional changes.ResultsKetamine-induced altered states were characterised predominantly by dissociative experiences such as disembodiment and ego transcendence; sensory disturbances were also common. Ketamine broadly decreased low-frequency power, with mean reductions largest at alpha (8-12 Hz) in parietal (-0.94 dB, P<0.001) and occipital (-1.8 dB, P<0.001) channel clusters. Significant decreases in alpha were identified in the precuneus and temporal-parietal junction.ConclusionsKetamine induces altered states of consciousness during periods of reduced alpha power in the precuneus and temporal-parietal junction. Modulation of these temporal-parietal loci are candidate mechanisms of the psychoactive effects of ketamine, given that this region is involved in multisensory integration, body representation, and consciousness.