Here is an interesting study on the effects of psychedelics measured from an EEG. For those of you who lived throught he 60′s, this is what was happening to you.
Some of the results may not be what you expected.
Effects of a Psychedelic, Tropical Tea, Ayahuasca, on the EEG Activity of the Human Brain during a Shamanistic Ritual - MAPS Magazine, Spring 2001
By Erik Hoffmann, Jan M. Keppel Hesselink, Yatra-W.M. da Silveira Barbosa
EEG data 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. Ayahuasca seems to open up the individual to his feelings and provide personal, psychological insights, and thus it may be a valuable adjunct to psychotherapy.
Also an excerpt from the study:
EEG research of psychedelics.
The majority of EEG studies done on psychedelics appeared in the scientific journals some 30 years ago before these compounds were banned. Wikler (1954), Itil (1968) and Fink (1978) are all in agreement that psychedelics, regardless of the substance (LSD, mescaline, psilocybin), produce decreases in slow wave (alpha and theta) activity together with increases of fast (beta) activity. This low amplitude, desynchronized EEG pattern induced by psychedelics reflect an activation of the brain and is in opposition to the highly synchronized alpha pattern observed during deep relaxation. Fink (1978) found that regardless of the nature of the drug administered, EEG synchronization (alpha/theta waves) was associated with euphoria, relaxation, and drowsiness; while EEG desynchronization was associated with anxiety, hallucinations, fantasies, and illusions. Don et al. (1998) found an increase of high frequency beta (’40Hz’) with no significant change of alpha and theta activity in the EEG following the ingestion of ayahuasca. All the above studies indicate that most psychedelic compounds tend to suppress low EEG frequency activity (alpha and theta) and enhance beta activity reflecting an activation of the brain. However, other psychedelic-like compounds such as marihuana and MDMA (ecstasy) seem to have the opposite effect and increase alpha activity. In a recent, controlled placebo study, an increase of EEG alpha power, correlating with intense euphoria, was found after smoking marihuana (Lukas, et al., 1995).
Long-term effects of the use of psychedelics, using qEEG monitoring, have rarely been studied. However, in a recent study of 23 recreational MDMA users Dafters et al. (1999) found that the use of MDMA was positively correlated with absolute power in the alpha (8-12Hz) and beta (12-20Hz) frequency bands. These findings were supported recently by another study by Gamma et al. (2000) who found global increases of theta, alpha and beta power in a group of regular MDMA users compared to a control group.
You can download the full PDF version here.