Effects of a Psychedelic, Tropical Tea, Ayahuasca, on the Electroencephalographic (EEG) Activity of the Human Brain during a Shamanistic Ritual, Erik Hoffmann et al., 2001

Effects of a Psychedelic, Tropical Tea, Ayahuasca, on the Electroencephalographic (EEG) Activity of the Human Brain during a Shamanistic Ritual

Erik Hoffmann, Jan M. Keppel Hesselink, Yatra-W.M. da Silveira Barbosa

MAPS Bulletin, Multidisciplinary Association for Psychedelic Studies, USA, Spring 2001, pp 25-30



Eight channels of EEG from 12 volunteers participating in a workshop in Brazil were recorded under field conditions before and after a shamanistic ritual in which the psychoactive tea, ayahuasca, was consumed. Following three doses of the tea, the subjects showed strong and statistically significant increases of both EEG alpha (8-13Hz) and theta (4-8Hz) mean amplitudes compared to baseline while beta (13-20Hz) amplitudes were unchanged. The strongest increases of alpha activity were observed in the occipital lobes while alpha was unchanged in the frontal lobes. Theta amplitudes, on the other hand, were significantly increased in both occipital and frontal areas. Our data do not support previous findings of cortical activation with decreased alpha and increased beta activity caused by psychedelics (e.g. LSD, mescaline, psilocybin). They rather point to a similarity between the altered states produced by ayahuasca and marihuana which also stimulates the brain to produce more alpha waves. We suggest that these findings of increased EEG alpha and theta activity after drinking ayahuasca reflect an altered state of consciousness. In this state the subjects reported increased awareness of their subconscious processes. This is an altered state comparable to, however more profound than, the meditative state. Our results suggest that ingesting Ayahuasca may provide individuals with increased access to subconscious processes and feelings while in a wakeful, relaxed state. Thus, Ayahuasca has the potential to become a potent tool in the process of psychotherapy.



Pharmacology. Ayahuasca is a beverage extracted from plants in the Amazonian rain forest. By boiling the bark of the tree Banisteriopsis caapi with the leaves of the plant Psychotria viridis a psychoactive brew is made. The Psychotria viridis contains the short-acting psychoactive agent dimethyltryptamine (DMT) which has a structural similarity to serotonin. When DMT binds to neuronal receptors in the brain it causes changes in cognition and state of consciousness. However, DMT is orally active only in the presence of MAO inhibitors such as the beta-carbolines of the Banesteriopsis bark. Thus, the interaction between the DMT and beta-carbolines is the basis of the psycho-activity of ayahuasca (McKenna et al., 1984).

Ayahuasca has a long history of safe and beneficial use for spiritual and healing purposes among large numbers of indigenous people in South America (Metzner, R., 1999). Only recently has Western science become interested in studying ayahuasca scientifically. In 1993 the Hoasca Project, a multinational, biomedical study of the ayahuasca tea, took place in the Brazilian Amazon Basin and the tea’s pharmacological, physiological and psychological effects on humans were studied (McKenna, D.J. et al., 1998; Callaway, J.C., et al., 1999, Grob, C.S., et al., 1996).