Topographic pharmaco‐EEG mapping of the effects of the South American psychoactive beverage ayahuasca in healthy volunteers
British Journal of Clinical Pharmacology – June 01, 2002
Source: OpenAlex
Summary
Ayahuasca, a traditional South American beverage, significantly alters brain activity, as shown by a study involving 18 experienced volunteers. Participants received low and high doses of ayahuasca (0.6 and 0.85 mg DMT per kg). Results indicated substantial dose-dependent increases in subjective effects measured by the Hallucinogen Rating Scale. Notably, absolute power decreased by approximately 20.20 µV² in total power and 2.70 µV² in theta power at peak times (90 minutes post-high dose). EEG changes began within 30 minutes, peaking between 45-120 minutes before returning to baseline after 4-6 hours.
Abstract
Aims Ayahuasca is a traditional South American psychoactive beverage used in Amazonian shamanism, and in the religious ceremonies of Brazilian‐based syncretic religious groups with followers in the US and several European countries. This tea contains measurable amounts of the psychotropic indole N , N ‐dimethyltryptamine (DMT), and β‐carboline alkaloids with MAO‐inhibiting properties. In a previous report we described a profile of stimulant and psychedelic effects for ayahuasca as measured by subjective report self‐assessment instruments. In the present study the cerebral bioavailability and time‐course of effects of ayahuasca were assessed in humans by means of topographic quantitative‐electroencephalography (q‐EEG), a noninvasive method measuring drug‐induced variations in brain electrical activity. Methods Two doses (one low and one high) of encapsulated freeze‐dried ayahuasca , equivalent to 0.6 and 0.85 mg DMT kg −1 body weight, were administered to 18 healthy volunteers with previous experience in psychedelic drug use in a double‐blind crossover placebo‐controlled clinical trial. Nineteen‐lead recordings were undertaken from baseline to 8 h after administration. Subjective effects were measured by means of the Hallucinogen Rating Scale (HRS). Results Ayahuasca induced a pattern of psychoactive effects which resulted in significant dose‐dependent increases in all subscales of the HRS, and in significant and dose‐dependent modifications of brain electrical activity. Absolute power decreased in all frequency bands, most prominently in the theta band. Mean absolute power decreases (95% CI) at a representative lead (P3) 90 min after the high dose were −20.20±15.23 µV 2 and −2.70±2.21 µV 2 for total power and theta power, respectively. Relative power decreased in the delta (−1.20±1.31% after 120 min at P3) and theta (−3.30±2.59% after 120 min at P3) bands, and increased in the beta band, most prominently in the faster beta‐3 (1.00±0.88% after 90 min at P3) and beta‐4 (0.30±0.24% after 90 min at P3) subbands. Finally, an increase was also seen for the centroid of the total activity and its deviation. EEG modifications began as early as 15–30 min, reached a peak between 45 and 120 min and decreased thereafter to return to baseline levels at 4–6 h after administration. Conclusions The central effects of ayahuasca could be objectively measured by means of q‐EEG, showing a time pattern which closely paralleled that of previously reported subjective effects. The modifications seen for the individual q‐EEG variables were in line with those previously described for other serotonergic psychedelics and share some features with the profile of effects shown by pro‐serotonergic and pro‐dopaminergic drugs. The q‐EEG profile supports the role of 5‐HT 2 and dopamine D 2 ‐receptor agonism in mediating the effects of ayahuasca on the central nervous system.