Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography
Using LORETA on EEG from 18 volunteers given encapsulated ayahuasca (0.85 mg DMT/kg), the study found significant decreases in alpha‑2, delta, theta and beta‑1 power 60–90 minutes after dosing versus placebo. These reductions were localised to the temporo‑parieto‑occipital junction and temporomedial/frontomedial regions, paralleled increased Hallucinogen Rating Scale scores, and implicate unimodal/heteromodal association cortices and limbic structures in ayahuasca’s psychological effects.
Authors
- Jordi Riba
- Maria Barbanoj
Published
Abstract
<i>Ayahuasca,</i> a South American psychotropic plant tea obtained from <i>Banisteriopsis caapi</i> and <i>Psychotria viridis</i>, combines monoamine oxidase-inhibiting β-carboline alkaloids with N,N-dimethyltryptamine (DMT), a psychedelic agent showing 5-HT<sub>2A</sub> agonist activity. In a clinical research setting, <i>ayahuasca</i> has demonstrated a combined stimulatory and psychedelic effect profile, as measured by subjective effect self-assessment instruments and dose-dependent changes in spontaneous brain electrical activity, which parallel the time course of subjective effects. In the present study, the spatial distribution of <i>ayahuasca</i>-induced changes in brain electrical activity was investigated by means of low-resolution electromagnetic tomography (LORETA). Electroencephalography recordings were obtained from 18 volunteers after the administration of a dose of encapsulated freeze-dried <i>ayahuasca</i> containing 0.85 mg DMT/kg body weight and placebo. The intracerebral power density distribution was computed with LORETA from spectrally analyzed data, and subjective effects were measured by means of the Hallucinogen Rating Scale (HRS). Statistically significant differences compared to placebo were observed for LORETA power 60 and 90 min after dosing, together with increases in all six scales of the HRS. <i>Ayahuasca</i> decreased power density in the alpha-2, delta, theta and beta-1 frequency bands. Power decreases in the delta, alpha-2 and beta-1 bands were found predominantly over the temporo-parieto-occipital junction, whereas theta power was reduced in the temporomedial cortex and in frontomedial regions. The present results suggest the involvement of unimodal and heteromodal association cortex and limbic structures in the psychological effects elicited by <i>ayahuasca</i>.
Research Summary of 'Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography'
Introduction
Riba and colleagues introduce ayahuasca as a traditional South American plant tea combining Banisteriopsis caapi, which supplies monoamine oxidase (MAO)–inhibiting ß-carbolines, with Psychotria viridis, a source of the short-acting psychedelic N,N-dimethyltryptamine (DMT). Because the ß-carbolines inhibit MAO, orally ingested DMT becomes bioavailable and produces acute perceptual, cognitive and mood effects that have been documented subjectively and in scalp electroencephalography (EEG) as dose-dependent reductions in spectral power and acceleration of centre-of-gravity frequency. Previous functional imaging work with related indoleamine psychedelics (for example, psilocybin) has shown metabolic increases in prefrontal regions, but the regional cortical generators of ayahuasca-induced EEG changes had not been assessed using source-localisation techniques available at the time. The present study therefore set out to map the intracerebral sources of ayahuasca-induced changes in spontaneous EEG using low-resolution electromagnetic tomography (LORETA). The authors aimed to identify which cortical and paralimbic regions show altered current density across classical EEG frequency bands after a single oral dose of encapsulated, freeze-dried ayahuasca, and to relate those regional effects to concurrently measured subjective psychedelic effects.
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Study Details
- Study Typeindividual
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- APA Citation
Riba, J., Anderer, P., Jané, F., Saletu, B., & Barbanoj, M. J. (2004). Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography. Neuropsychobiology, 50(1), 89-101. https://doi.org/10.1159/000077946
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