Characteristic patterns of EEG oscillations in sheep (Ovis aries) induced by ketamine may explain the psychotropic effects seen in humans.
A U Nicol, A J Morton
Scientific Reports June 11, 2020 DOI: 10.1038/s41598-020-66023-8 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 12 |
| Population | Sheep |
| Intervention | Ketamine |
| Dose | 24 mg/kg |
| Topics | Esketamine Ketamine |
| Key findings | Ketamine produces alternating low and high frequency EEG oscillations during recovery from sedation, and at high doses can cause complete cessation of cortical EEG activity. |
Abstract
Ketamine is a valuable anaesthetic and analgesic that in recent years has gained notoriety as a recreational drug. Recently, ketamine has also been proposed as a novel treatment for depression and post-traumatic stress disorder. Beyond its anaesthetic actions, however, the effects of ketamine on brain activity have rarely been probed. Here we examined the cortical electroencephalography (EEG) response to ketamine of 12 sheep. Following ketamine administration, EEG changes were immediate and widespread, affecting the full extent of the EEG frequency spectrum measured (0-125 Hz). After recovery from sedation during which low frequency activity dominated, the EEG was characterised by short periods (2-3 s) of alternating low (<14 Hz) and high (>35 Hz) frequency oscillation. This alternating EEG rhythm phase is likely to underlie the dissociative actions of ketamine, since it is during this phase that ketamine users report hallucinations. At the highest intravenous dose used (24 mg/kg), in 5/6 sheep we observed a novel effect of ketamine, namely the complete cessation of cortical EEG activity. This persisted for up to several minutes, after which cortical activity resumed. This phenomenon is likely to explain the 'k-hole', a state of oblivion likened to a near death experience that is keenly sought by ketamine abusers.
Comparable studies
Other observational and cohort studies on ketamine, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Taming the Ketamine Tiger Volunteers from a prison population | 2010 | Observational study | n = 20 |
| Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin Humans | 2017 | Observational study | |
| Disruption of Frontal–Parietal Communication by Ketamine, Propofol, and Sevoflurane Surgical patients undergoing induction of anesthesia with intravenous ketamine | 2013 | Observational cohort | n = 30 |
| Do the dissociative side effects of ketamine mediate its antidepressant effects? Treatment-resistant inpatients with major depressive disorder or bipolar disorder | 2014 | Observational cohort | n = 108 |
| Concomitant BDNF and sleep slow wave changes indicate ketamine-induced plasticity in major depressive disorder Patients with treatment-resistant major depressive disorder | 2012 | Observational cohort | n = 30 |
Citations in the library
Cited by 10
- A hidden Markov model reliably characterizes ketamine-induced spectral dynamics in macaque local field potentials and human electroencephalograms PLoS Computational Biology August 18, 2021
- A neuroscientific model of near-death experiences. Nature Reviews Neurology June 1, 2025
- Subthreshold repetitive transcranial magnetic stimulation suppresses ketamine-induced poly population spikes in rat sensorimotor cortex Frontiers in Neuroscience October 21, 2022
- An Update of Ketamine Illicit Use Ketamine Revisited - New Insights into NMDA Inhibitors September 14, 2022
- Olfactory bulb circuits drive ketamine-enhanced high-frequency oscillations via kainate and GABAergic mechanisms. Neuropharmacology May 6, 2026
and 5 more in the library
Cites 9
- Ketamine: a paradigm shift for depression research and treatment Neuron March 1, 2019
- Ketamine – More mechanisms of action than just NMDA blockade Trends in Anaesthesia and Critical Care March 22, 2014
- Evidence that Subanesthetic Doses of Ketamine Cause Sustained Disruptions of NMDA and AMPA-Mediated Frontoparietal Connectivity in Humans Journal of Neuroscience August 19, 2015
- A Review of the Nonmedical Use of Ketamine: Use, Users and Consequences Journal of Psychoactive Drugs December 1, 2000
- A REVIEW OF KETAMINE ABUSE AND DIVERSION Depression and Anxiety August 1, 2016
and 4 more in the library