ELECTROENCEPHALOGRAPHIC SPECTRAL MARKERS OBSERVED DURING THE ACUTE EFFECTS OF AYAHUASCA AND ITS RELATION TO THE PSYCHEDELIC EXPERIENCE
Ayahuasca, electroencephalography, spectral analysis, alpha power, dream, HRS, MEQ
The ayahuasca is a drink with psychedelic properties largely used by indigenous populations from the Amazon basin. It contains the psychedelic tryptamine N,N-dimethyltriptamine (DMT), and monoamine oxidase inhibitors (iMAO), such as harmine and harmaline. The ayahuasca is considered to be a serotonergic psychedelic, capable of inducing an altered state of consciousness with similarities to an oneiric experience, with intense alterations in perception, though, humor, emotion, and mystical-type experiences. The neural correlates of its acute effects have been investigated by different neuroimaging techniques, including electroencephalography (EEG). In this study, we explored EEG spectral changes in 50 healthy volunteers, using a randomized double-blind placebo-controlled experimental design. Half of the volunteers received ayahuasca, while the other half received placebo. After dosing, the volunteers were monitored by an EEG equipment for approximately 4-hours. Aiming to improve data quality, the volunteers were asked to perform 2 simple tasks in three specific moments: before intake, 2h and 4h after intake. For the first task, they should try to stay awake, and alternate moments of eyes open (20 seconds) and eyes closed (40 seconds) for 5 minutes. For the second task, they should keep their eyes closed, trying to stay awake, for another 5 minutes. The spectral analysis (2h) found the alpha power to be significantly lower for the ayahuasca group when compared to placebo in occipital and right temporoparietal regions. Moreover, we found a significant increase in theta power on the right temporoparietal region, also 2h after the intake. Correlation analysis revealed correspondences between the alpha power (2h) and individual scores on two scales used to measure psychedelic effects – the Hallucinogen Rating Scale (HRS) and the Mystical Experience Questionnaire (MEQ). Additionally, we also present curious events found during visual inspection of EEG tracings. Overall, our results suggest that the inhibition of alpha oscillations in posterior brain regions play an important role on the psychedelic experience, maybe sharing mechanisms present during the oneiric experience.