How does ayahuasca affect the brain?

With thousands of users in Brazil and around the world, ayahuasca tea has attracted scientific interest in understanding how the substance affects the human brain.

Ayahuasca is a hallucinogenic drink prepared from the bark and leaves of South American plants, traditionally used by Amazonian peoples for medicinal or religious purposes.

There is evidence that people first used ayahuasca at least a thousand years ago.

A study by scientists at Imperial College London has produced extensive results showing how the substance affects the quality of individuals' experience of consciousness.

The study, published in March 2023 in the scientific journal Proceedings of the National Academy of Sciences (PNAS) , was the first to collect such detailed data on the effects of psychedelics on the brain.

For this study, 20 healthy volunteers were invited to receive a 20 mg intravenous dose of the main psychoactive compound in ayahuasca, DMT (dimethyltryptamine).

Detailed data from the volunteers' brain images were then analyzed before, during and after exposure to the substance.

A summary published on the Imperial College London website revealed how the powerful psychedelic compound DMT changed brain function.

To visualize the brain's response, volunteers underwent two types of analyses: functional magnetic resonance imaging (fMRI) and electroencephalography (EEG).

In total, the psychedelic experience lasted 20 minutes, with the researchers regularly asking participants to rate the intensity of the experience on a scale of 0 to 10.

Ultimately, increased connectivity was seen in the brain, with more communication between different parts. The biggest changes occurred in 'higher level' brain areas, such as imagination.

Furthermore, exposure to DMT was found to mainly alter the areas responsible for language, memory and complex decision-making, which had a profound impact on the volunteers' brains, according to The Guardian.

In other words, the areas of the brain from which we project reality have become hyper-connected and communication between different areas of the brain has become more fluid and flexible.

In practice, "People describe leaving this world and breaking through into another that is incredibly immersive and richly complex," said Robin Carhart-Harris, the founder of the Center for Psychedelic Research at Imperial College London and author of the article, to The Guardian.

Carhart-Harris added that some people experience "sometimes being populated by other beings that they feel might hold special power over them, like gods."

The scientist also emphasized, “The way the brain worked changed into something radically more anarchic.”

Today, Carhart-Harris is a professor of neurology and psychiatry at the University of California, San Francisco.

Another description of the effects of ayahuasca, published by Imperial College London, says that the altered state of consciousness causes distorted and bizarre visions, and a feeling of being in an alternate dimension, similar to what is described by people who are almost -have had death experiences.

Christopher Timmermann, another author of the paper, noted: "The stronger the intensity of the experience, the more hyperconnected were those brain areas."

He is currently active at Imperial College London, where he leads the DMT research group, specializing in psychedelics. His empirical and theoretical work focuses on the neuroscience, psychiatry, psychology and ethics of psychedelics and their applications in mental health care.

Photo: Instagram @christophertimmermann

“Psychedelics can actually be very powerful scientific tools for understanding how brain activity is related to conscious experience,” Carhart-Harris said.