PM506. Psilocybin Clinical Trial: Acute Effects and its relationship to the brain activity as measured by quantitative EEG

Abstract

Abstract Objectives: The serotonergic hallucinogen psilocybin, has profound effects on the human mind, which can be characterized by alteration in perception, thinking disorder and strong emotional salience. The character of the altered state of consciousness induced by hallucinogens is hardly predictable; while an important role has the environment in which psilocybin is administered (setting). Methods: Twenty volunteers completed the psilocybin (0.26 mg/kg, average dose 18.7 mg) session in a double-blind, placebo-controlled arrangement in a comfortable living-room-like setting. This study describes the phenomenology (evaluated objectively by Brief Psychiatric Rating Scale (BPRS) and subjectively by Altered States of Consciousness Scale (ASCS)), physiological parameters and pharmacokinetics of psilocybin intoxication. It also focuses on the relationship between electrophysiological measures of brain activity and phenomenology. Results: The effects of psilocybin peaked in 60 minutes (average blood levels 20 ng/ml) and subsided after 6 hours (average blood levels 4 ng/ml). Psilocybin induced mydriasis (rarely anisocoria), an increase in blood pressure and heart rate compared to placebo. A significant increase of psychopathology was documented by BPRS (subscale thought disorder and hallucinations) and ASCS (subscales visual restructuralization, oceanic boundlessness and to a lesser extent anxious ego dissolution). Psilocybin decreased the EEG spectral power in alpha frequency band, however increased the power of gamma oscillations. The LORETA analysis revealed the source of decreased alpha in midline parietal structures and occipital lobes. The increase in higher frequencies was pronounced in large temporal areas. EEG findings will be correlated with neuropsychiatric scales. Conclusion: We confirmed the safety and beneficial effects of psilocybin administration in a clinical trial under controlled experimental conditions. The decrement of EEG alpha activity was observed mainly in brain structures involved in Default Mode Network, which is thought to represent introspective processes. We hope that these findings will help facilitate future clinical trials using psychedelic substances in patients. This study was supported by the projects IGA MHCR NT/13897, “National Institute of Mental Health (NIMH–CZ)”, grant number ED2.1.00/03.0078, and by the European Regional Development Fund.