New World Tryptamine Hallucinogens and the Neuroscience of Ayahuasca

This book chapter (2016) provides an overview of major tryptamine-containing New World hallucinogens with a special focus on ayahuasca, for which the authors propose a model of brain effects in which ayahuasca reduces top-down constraints and facilitates bottom-up information transfer.

Abstract

“New World indigenous peoples are noted for their sophisticated use of psychedelic plants in shamanic and ethnomedical practices. The use of psychedelic plant preparations among New World tribes is far more prevalent than in the Old World. Yet, although these preparations are botanically diverse, almost all are chemically similar in that their active principles are tryptamine derivatives, either DMT or related constituents. Part 1 of this paper provides an ethnopharmacological overview of the major tryptamine-containing New World hallucinogens. Part 2 focuses on ayahuasca and its effects on the human brain. Using complementary neurophysiological and neuroimaging techniques, we have identified brain areas involved in the cognitive effects induced by this complex botanical preparation. Initial SPECT data showed that ayahuasca modulated activity in higher order association areas of the brain. Increased blood perfusion was observed mainly in anterior brain regions encompassing the frontomedial and anterior cingulate cortices of the frontal lobes, and in the medial regions of the temporal lobes. On the other hand, applying spectral analysis and source location techniques to cortical electrical signals, we found changes in neuronal activity that predominated in more posterior sensory-selective areas of the brain. Now, using functional connectivity analysis of brain oscillations we have been able to reconcile these seemingly contradictory findings. By measuring transfer entropy, a metric based on information theory, we have shown that ayahuasca temporarily modifies the ordinary flow of information within the brain. We propose a model in which ayahuasca reduces top-down constraints and facilitates bottom-up information transfer. By simultaneously enhancing endogenous cortical excitability and reducing higher-order cognitive control, ayahuasca temporarily disrupts neural hierarchies allowing inner exploration and a new outlook on reality.”

Authors: Dennis McKenna & Jordi Riba

Summary of New World Tryptamine Hallucinogens and the Neuroscience of Ayahuasca

Botany, Chemistry, and Ethnopharmacology of New World Tryotamine Hallucinogens

Introduction

The indigenous cultures of the New World are infinitely more sophisticated in their knowledge and utilization of vision-producing plants than their Old World counterparts, but this asymmetry has never been satisfactorily explained. The Finno-Ugric peoples settled west of the Urals sometime after the end of the last Ice Age, and used the Amanita muscaria mushroom as an intoxicant. There is no information on whether these cultures also used Amanita, or whether they had any cultural relation to the Finno-Ugric peoples.

To access this content, you must purchase one of the following memberships: Sprout Membership, Pro Membership, Pro Membership Unlimited, Business Membership or Business Membership Unlimited. The membership will give you access to exclusive data, including summaries of psychedelic research papers, extended company info, and our member-only visualisations. Save yourself multiple hours each week by accessing Blossom’s resource library.