Ketamine produces distinct brain-wave patterns that may be linked to its therapeutic effects. General anesthesia selectively blocks one of these patterns—theta oscillations—while leaving another pattern, beta-gamma oscillations, intact. In 52 participants, ketamine given during anesthesia preserved beta-gamma power increases but eliminated the characteristic theta augmentation seen during awake administration. This suggests that different neurophysiologic effects of ketamine can be separated, offering a way to investigate which brain-wave changes underlie its antidepressant, analgesic, or dissociative properties.
A standardized propofol-based anesthesia protocol with EEG monitoring and verbal priming about dreaming led 69% of 452 surgical patients to report dreaming, and 93% of those who received all protocol elements did so. Most dreams were positive (86%), and dreamers reported higher subjective sleep quality than nondreamers. The protocol was safe, with no intraoperative awareness, and recovery times and medication use did not differ between groups. Adherence was high for most elements but low for the no-stimulation emergence period. The approach is feasible in routine clinical care and aligns with Enhanced Recovery After Surgery principles.
Ketamine produces dissociative, analgesic, and antidepressant effects, but it is unclear whether its underlying neurophysiological signatures can be separated. In this observational cohort study, 52 participants (healthy volunteers, elective surgery patients, and patients with depression) received a subanesthetic infusion of ketamine or placebo, with or without general anesthesia. When ketamine was given under general anesthesia, its characteristic low-frequency brain wave augmentation was absent, while high-frequency power modulation was preserved. This selective modulation suggests a method for investigating the distinct roles of high- and low-frequency neural activity in ketamine's behavioral effects.