A single dose of ketamine (0.54 mg/kg infused over 30 minutes) rapidly alters brain electrical activity in healthy volunteers, producing a decrease in prefrontal theta cordance—a QEEG measure linked to cerebral blood flow—and an increase in central region theta cordance within 10 to 30 minutes. These changes resemble those seen after one week of treatment with standard antidepressants in people who respond to them, but occur much faster. The prefrontal theta cordance reduction correlated with ketamine and norketamine blood levels at 10 minutes. The findings suggest that theta cordance reduction could serve as a marker and predictor of ketamine's rapid antidepressant effect, a hypothesis warranting testing in depressed patients.
Psilocybin, a serotonergic psychedelic with antidepressant potential, altered sleep architecture in healthy volunteers the night after administration. In a randomized, double-blinded trial, 20 healthy adults (10 women, ages 28–53) received psilocybin or placebo. Psilocybin prolonged REM sleep latency and showed a trend toward reduced total REM sleep duration, with no changes in NREM sleep or whole-night EEG power spectra. Contrary to expectations, psilocybin suppressed slow-wave activity in the first sleep cycle, providing no evidence for sleep-related neuroplasticity. The findings suggest that psilocybin's antidepressant properties may involve sleep changes, possibly through different mechanisms than those of classical antidepressants.
Sleep in people with recurrent isolated sleep paralysis (RISP) is disturbed even outside episodes and beyond REM sleep. Spectral analysis of full-night polysomnography recordings from 17 RISP patients and 17 controls revealed significantly higher theta power in REM and NREM 2 stages in RISP patients, with a similar trend in other stages. Alpha power showed a downward trend in deep sleep. EEG microstate analysis during NREM 3 found preserved prototypical generators but abnormal temporal dynamics, including altered transitions between microstates C and D and between A and B. The findings suggest that understanding RISP requires examining processes beyond REM, and microstate dynamics may serve as functional biomarkers.