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Scientists have identified a hallmark signature produced by psychedelic drugs in the human brain when users experience their mind-altering effects.
The “neural fingerprint” of the psychedelic trip was spotted among hundreds of brain scans of people on LSD, psilocybin, DMT, mescaline and ayahuasca, pointing to a shared impact on the brain’s behaviour.
The finding emerged from a major study that combined 11 brain imaging datasets from around the world in an effort to build a reliable picture of how the substances temporarily rewire the brain.
The insights are increasingly important as researchers investigate the drugs in clinical trials as potential therapies for severe mental health and neurological conditions such as depression, schizophrenia and post-traumatic stress disorder.
“These five drugs that have never been analysed together for their impact on the brain have certain effects in common in how they change brain function,” said Dr Danilo Bzdok, a senior author on the study, from McGill University in Montreal, Canada.
“All five drugs dissolve the common order, the usual hierarchy of brain systems,” he added. “They flatten the hierarchy and that probably underlies what some people describe as this raw access to one’s own consciousness.”
Scientists have long sought to understand how psychedelics work in the brain to produce hallucinations and what some describe as the dissolution of the self, when people feel their sense of identity disintegrate. But many studies have been small, making it hard to reach confident conclusions.
Writing in Nature Medicine, Bzdok and his colleagues analysed more than 500 brain scans from 267 people in five countries in what they believe is the largest study into psychedelics and the human brain to date.
While there were some differences in how the drugs changed brain activity, there was substantial overlap in their impact on how regions of the brain communicated with one another. The most striking effect was stronger communication between brain networks that engage in higher-level thinking and more primitive networks linked to vision and sensation.
“You have an unleashed cross-talk between brain systems – they are wildly communicating with each other,” Bzdok said. “It’s excessive cross-talk between brain systems.”
Further changes were spotted deeper in the brain in regions linked to habits, learning and movement, the study found. Contrary to some previous claims, the study found little reliable evidence that some individual brain networks “disintegrate” on psychedelics.
According to Bzdok, the work helps to put psychedelic research on a surer footing, which is crucial if the drugs are to become widespread therapies for mental health conditions.
“We saw that this field is emerging, and it’s very important, but they are on shaky ground; they are building houses on matches,” Bzdok said. “This is why we started the study with the ambition to provide a solid foundation.”
Dr Emmanuel Stamatakis, a senior co-author on the study from the University of Cambridge, said: “This field is moving quickly. If psychedelic research is to mature responsibly, it needs large-scale, coordinated evidence.”
