Effects of Ayahuasca on the human EEG

Ayahuasca ingestion increased 36-44 Hz ("40 Hz") brain wave power in posterior scalp regions, consistent with intensified visual imagery. The study recorded EEG from 11 members of the Santo Daime Doctrine before and after drinking ayahuasca. Power increases appeared from left occipital-temporal-parietal electrodes with eyes closed and spread across most of the posterior scalp with eyes open. Slow theta and alpha rhythms tended to decrease, while 14-30 Hz beta power increased. Analysis of four ayahuasca samples showed average doses of 55.6 mg harmine, 43.9 mg tetrahydroharmine, 41.3 mg DMT, 4.6 mg harmaline, and 3.1 mg harmol per 75 ml. The DMT concentration was sufficient for psychoactive effects, with β-carbolines providing MAO inhibition to maintain oral activity.

Study at a glance

Abstract

EEG data were recorded under field conditions from 11 members of the Santo Daime Doctrine, a Brazilian shamanistic religion, before and after ingesting the psychoactive alkaloid preparation, ayahuasca, or daime, as they term it. Post-ingestion, we observed increases in power in the 36-44 Hz frequency band ("40 Hz") from the left occipital-temporal-parietal scalp electrodes in the eyes-closed condition, which extended to most of the posterior scalp in the eyes-open condition. The results are consistent with many reports that ayahuasca intensifies visual imagery. These results are discussed in terms of a thalamocortical model of the role of 40 Hz activity in brain function and conscious experience. We also noted tendencies toward decreases in the power of slow (theta and alpha) brain rhythms, and increases in the 14-30 Hz beta band, in accord with studies reported 30 years ago with other consciousness-altering compounds. Analysis of four ayahuasca samples yielded an average composition per ingested dose (75 ml) of 55.6 mg harmine, 43.9 mg tetrahydroharmine, 41.3 mg N,N-dimethyltryptamine (DMT), 4.6 mg harmaline, and 3.1 mg harmol. The DMT appeared to be of sufficient concentration to promote psychoactive effects, while the β-carbolines functioned to supply MAO inhibitors necessary to prevent degradation of DMT and to maintain its oral activity.