Psilocybin intoxication did not affect daytime or sleep-related declarative memory consolidation in a small sample exploratory analysis.

Psilocybin is investigated as a fast-acting antidepressant used in conjunction with psychotherapy. Intact cognitive functions, including memory, are one of the basic conditions of effective psychedelic-assisted therapy. While cognitive and memory processing is attenuated on various domains during psilocybin intoxication, the effect of psilocybin on the consolidation of memories learned outside of acute intoxication is not known. Thus the main aim of the current study was to test the effects of psilocybin on (A) memory consolidation of previously learned material just after the psilocybin session and (B) on overnight memory consolidation the night just after the psilocybin session. 20 healthy volunteers (10 M/10F) were enrolled in a placebo-controlled, double-blind, cross-over design. Effects on declarative memory consolidation in condition (A) The Groton Maze Learning Task and Rey Auditory Verbal Learning Test were used, and for (B) the Pair Associative Learning Test was used. We did not find psilocybin to improve memory consolidation. At the same time, we did not find psilocybin to negatively affect memory consolidation in any of the tests used. This evidence adds to the safety profile for the use of psilocybin.

Psilocybin-Mediated Attenuation of Gamma Band Auditory Steady-State Responses (ASSR) Is Driven by the Intensity of Cognitive and Emotional Domains of Psychedelic Experience.

Psilocybin is a classical serotoninergic psychedelic that induces cognitive disruptions similar to psychosis. Gamma activity is affected in psychosis and is tightly related to cognitive processing. The 40 Hz auditory steady-state responses (ASSR) are frequently used as indicators to test the ability to generate gamma activity. Based on previous literature, we studied the impact of psilocybin on 40 Hz ASSR in healthy volunteers. The study was double blind and placebo controlled with a crossover design. A sample of 20 healthy subjects (10M/10F) received psilocybin orally 0.26 mg/kg or placebo. Participants were measured four times in total, one time before ingestion of psilocybin/placebo and one time after ingestion, during the peak of intoxication. A series of 500 ms click trains were used for stimulation. Psilocybin induced a psychedelic effect and decreased 40 Hz ASSR phase-locking index compared to placebo. The extent of the attenuation was related to Cognition and Affect on the Hallucinogen Rating Scale. The current study shows that psilocybin lowers the synchronization level and the amplitude of 40 Hz auditory steady-state responses, which yields further support for the role of gamma oscillations in cognitive processing and its disturbance.