Behavioural brain research
January 5, 2025
Santiago Castro-Zaballa, Joaquín González, Matías Cavelli et al.
4 citations
In cats, high-frequency oscillations (HFO, >100 Hz) in the brain's electrical activity are linked to breathing during wakefulness but not during sleep. A sub-anesthetic dose of ketamine increases the power of these HFO, and they remain tied to the inhalation phase of respiration. The enhanced HFO appear to originate in the olfactory bulb and travel to the prefrontal cortex. Blocking the nostrils reduces the ketamine-enhanced HFO in both regions. Auditory stimulation does not affect these oscillations. The findings suggest that ketamine's enhancement of respiration-coupled HFO may disrupt cortical information processing, potentially contributing to its neuropsychiatric effects.
Neuropharmacology
September 15, 2026
Taisiia Prosvirova, Wiktoria Podolecka, Jacek Wrobel et al.
Ketamine rapidly reorganizes fast brain rhythms differently across cortical networks. In freely moving rats, neocortical gamma power increased broadly, while the olfactory bulb showed suppressed gamma alongside robust high-frequency oscillations (HFO; 130-180 Hz). Local blockade of non-NMDA glutamate receptors in the olfactory bulb suppressed ketamine-enhanced HFO in the bulb, ventral striatum, and prefrontal cortex without affecting neocortical gamma, indicating separate circuit mechanisms. Within the bulb, a kainate receptor antagonist markedly reduced HFO, while AMPA receptor blockade had minimal effect. Blocking GABA-A receptors reduced HFO power while increasing gamma power, showing that fast inhibition is necessary for HFO expression. The findings suggest that tonic kainate-dependent depolarization recruits interneurons to generate an inhibitory network rhythm that drives HFO propagation through olfactory-limbic circuits.
Journal of psychopharmacology (Oxford, England)
July 24, 2025
Mark Jeremy Hunt, Jacek Wróbel
Subanesthetic doses of ketamine produce rapid psychotomimetic and long-lasting antidepressant effects, yet its mechanisms remain unclear. Neurophysiological recordings in freely moving rodents reveal that ketamine and other NMDAR antagonists markedly enhance high-frequency oscillations (HFO, >100 Hz) across olfactory and frontostriatal brain regions. This rhythm is remarkably coherent across distinct regions, modulated by slower oscillations, and driven largely by respiration-locked olfactory bulb activity. Similar activity has been observed in other mammals. This review is the first synthesis of studies on NMDAR antagonist-enhanced HFO, identifying gaps and urging more human research.