Shannon entropy of brain functional complex networks under the influence of the psychedelic Ayahuasca
Analysis of resting‑state fMRI using complex‑network methods shows that Ayahuasca increases the Shannon entropy of the brain functional network degree distribution and produces greater local but reduced global integration. These network changes support the entropic brain hypothesis and are discussed in relation to users’ reports of “mind‑expansion.”
Authors
- Fernanda Palhano-Fontes
- Draulio Araújo
Published
Abstract
The entropic brain hypothesis holds that the key facts concerning psychedelics are partially explained in terms of increased entropy of the brain’s functional connectivity. Ayahuasca is a psychedelic beverage of Amazonian indigenous origin with legal status in Brazil in religious and scientific settings. In this context, we use tools and concepts from the theory of complex networks to analyze resting state fMRI data of the brains of human subjects under two distinct conditions: (i) under ordinary waking state and (ii) in an altered state of consciousness induced by ingestion of Ayahuasca. We report an increase in the Shannon entropy of the degree distribution of the networks subsequent to Ayahuasca ingestion. We also find increased local and decreased global network integration. Our results are broadly consistent with the entropic brain hypothesis. Finally, we discuss our findings in the context of descriptions of “mind-expansion” frequently seen in self-reports of users of psychedelic drugs.
Research Summary of 'Shannon entropy of brain functional complex networks under the influence of the psychedelic Ayahuasca'
Introduction
Ayahuasca is an Amazonian psychoactive brew that contains N,N-dimethyltryptamine (DMT) together with harmala alkaloids that act as monoamine oxidase inhibitors (MAOIs). The beverage allows DMT to reach the brain and, like other classic psychedelics, can produce marked alterations of perception, cognition and self-experience. Interest in Ayahuasca has grown because of suggested therapeutic effects in conditions such as depression and addiction, and because neuroimaging methods now permit non-invasive study of whole-brain functional organisation in altered states of consciousness. Viol and colleagues set out to test a prediction of the entropic brain hypothesis: that psychedelics increase entropy of brain functional connectivity. Using resting-state fMRI collected before and after Ayahuasca ingestion, they applied concepts from graph theory and information theory to construct whole-brain functional networks and directly measure the Shannon entropy of the networks' degree distributions. The aim was to determine whether entropy increases under Ayahuasca and how that change relates to conventional network measures of local and global integration.
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Study Details
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- APA Citation
Viol, A., Palhano-Fontes, F., Onias, H., de Araujo, D. B., & Viswanathan, G. M. (2017). Shannon entropy of brain functional complex networks under the influence of the psychedelic Ayahuasca. Scientific Reports, 7(1). https://doi.org/10.1038/s41598-017-06854-0
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