EEG Gamma Coherence and Other Correlates of Subjective Reports During Ayahuasca Experiences

In two experienced ayahuasca users studied in a Brazilian jungle, EEG recordings showed increased global brain coherence in the 36-44 Hz and 50-64 Hz frequency bands during visual imagery compared to eyes-closed baselines. This widespread cortical hyper-coherence may relate to the intense synesthesia typical of ayahuasca experiences. Other findings included increased modal EEG alpha frequency and global power decreases across most frequency bands, consistent with prior psychedelic EEG literature. The exploratory case series suggests that analyzing single Hz bins rather than standard wide bands can be useful. The authors propose that increased global gamma coherence during peak psychedelic experiences may inform binding theory and invites comparison with advanced meditative states.

Study at a glance

Abstract

The current study examined QEEG power and coherence of ayahuasca experiences with two experienced participants in a Brazilian jungle setting. An exploratory case series design was adopted for naturalistic field research. EEGs recorded during visual imagery was compared to eyes-closed baselines. The most important findings were increases in global EEG coherence in the 36-44 Hz and 50-64 Hz frequency bands for both subjects. Widely distributed cortical hyper-coherence seems reasonable given the intense synesthesia during ayahuasca experiences. Other findings include increased modal EEG alpha frequency and global power decreases across the cortex in most frequency bands, which concur with the EEG of psychedelics literature. Exploratory analysis revealed the usefulness of analyzing single Hz bins over the standard wide-band analysis. The discovery-oriented naturalistic approach developed for this study resulted in potentially important findings. We believe that finding increases in global gamma coherence during peak psychedelic experiences might contribute to the discussion of binding theory. Also, in light of recent research with gamma coherence during advanced meditative conditions, our findings might further the comparison of shamanic psychedelic practices with meditation.