Predicting and exploring ayahuasca effects: Perception, mind-wandering, and EEG oscillations
Pretreatment clinical characteristics vs dose on the subjective psychedelic experience,
In this double-blind placebo-controlled trial (n=46) found that ayahuasca induced mystical experiences, altered perception, and changes in mind-wandering alongside decreased alpha and increased delta, theta, and beta EEG oscillations, with baseline brainwave patterns predicting the intensity of certain subjective effects.
“Background: Psychedelics induce profound changes in perception and thinking; however, little is known about the neural mechanisms and prediction of these effects.
Aims: Investigating ayahuasca-induced experiences, mind-wandering, and electroencephalogram (EEG) oscillations, beyond the prediction of subjective experiences by baseline EEG.
Methods: In a randomised, double-blind, placebo-controlled, parallel-arm design, 50 healthy volunteers received 1 mL/kg of ayahuasca or placebo. We measured subjective psychedelic experiences (Hallucinogen Rating Scale (HRS), Mystical Experience Questionnaire (MEQ)) and mind-wandering (Amsterdam Resting-State Questionnaire (ARSQ)). EEG signals were assessed before administration (+0h), and 2 hours (+2h) and 4 hours (+4h) post-administration. Relationships between subjective and EEG effects were examined.
Results: Ayahuasca, compared to placebo, induced subjective experiences, including changed perception, cognition, emotion (HRS), mystical experiences (MEQ), and visual, discontinuous, and content-laden thinking (ARSQ). Ayahuasca, compared to placebo, changed EEG oscillations, including decreased global alpha as well as increased frontomedial delta and right posterior theta and beta. Under ayahuasca, lower theta correlated with higher mystical experiences (MEQ) and higher alpha correlated with lower Thoughts about Nothing (ARSQ). Baseline global EEG oscillations predicted ayahuasca-induced experiences, with lower theta linked to higher interoception (HRS Heart Beat, HRS Rush, ARSQ Somatic Awareness) and lower beta linked to higher positive emotionality (HRS Happy).
Conclusion: Ayahuasca induced consciousness alterations, visual, bodily, emotional, and mystical experiences, chaotic and meaningful mind-wandering, and decreased especially alpha. While acute theta seems inversely related to mystical experiences, baseline theta and beta seem to inversely predict interoception and emotionality.“
Notes
Three key findings are highlighted in this study.
Ayahuasca reliably induces complex alterations in perception, emotion, cognition, and mystical experience in healthy individuals.
These experiences are accompanied by distinct EEG oscillatory signatures, especially alpha suppression and changes in delta/theta/beta bands.
Baseline EEG metrics can partially predict the character and intensity of ayahuasca-induced subjective effects, highlighting a neural basis for individual variation in psychedelic experiences.
These findings advance mechanistic understanding of how ayahuasca modulates brain activity and consciousness.
They provide a first step toward predictive biomarkers for individual responses to psychedelics, relevant for therapeutic research.
The link between EEG rhythms and subjective content also offers neurophysiological anchors for phenomena such as mystical experience and mind-wandering in altered states
Silva-Costa, N., Pessoa, J. A., Andrade, K. C., Mota-Rolim, S., Palhano-Fontes, F., Araujo, D. B., & Wießner, I. (2025). Predicting and exploring ayahuasca effects: Perception, mind-wandering, and EEG oscillations. Journal of Psychopharmacology, 02698811251389563. Read Paper
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