Study finds psilocybin can desynchronize brain networks, potentially enhancing its plasticity.
Sara Moser/Washington University School of Medicine in St. Louis
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Sara Moser/Washington University School of Medicine in St. Louis
In the name of science, Dr. Nico Dosenbach had scanned his own brain dozens of times. But this was the first time he had taken a psychotropic substance before sliding into the MRI tunnel.
“I was like I was plunged into a greater and greater strangeness,” he recalls. “I didn’t know where I was at all. Time stopped and I was everyone.”
Dosenbach, an associate professor of neurology at Washington University School of Medicine in St. Louis, had been given a high dose of psilocybin, the active ingredient in magic mushrooms, by his colleagues.
It was all part of a seven-person study designed to show how psilocybin produces its psychotropic effects.
The results, which appear in the journal Naturesuggest that psychedelic drugs work by disrupting certain brain networks, particularly the one that helps people form a sense of space, time, and self.
“For the first time, in a very high degree of detail, we understand which networks are changing, how intensely they are changing, and what persists after the experience,” says Dr. Petros Petridis of New York University’s Langone Center for Psychedelic Medicine, who wrote an editorial accompanying the study.
The research also looked closely at how these drugs temporarily improve the brain’s ability to adapt and change, a capacity known as plasticity.
“Disruptions in brain networks appear to be “at the root of the plasticity effects of psychedelics,” says Dr. Joshua Siegel, a researcher at the University of Washington and lead author of the study.
If true, he said, it could explain why psychedelics appear to help people with addiction or depression.
A cerebral journey
Dosenbach and other participants were randomly assigned to receive either a stimulant or 25 milligrams of psilocybin, a dose high enough to cause hallucinations.
“It was a really great experience for a neuroscientist,” he says.
“It’s really fascinating how your brain can break down, because the way something breaks tells you how something works.”
Dosenbach’s journey has taken him to places only a neuroscientist might go.
“I was inside the brain, surfing the brainwaves, and I was Marc Raichle,” he says, referring to Dr. Marcus Raichle, a colleague and co-author of the study, who also happens to be a prominent figure in the world of neuroscience.
As part of the study, participants’ brains were scanned an average of 18 times over a three-week period, with four of them repeating the experiment six to 12 months later.
“You bring in unique individuals multiple times,” Siegel says, “and you get a very detailed and precise map of their brain networks.”
The scans showed that psilocybin caused rapid and dramatic changes in certain brain networks. Typically, neurons in a given network become active at the same time, often in tandem with other networks as well.
“What happens during psilocybin administration is that populations of neurons that are normally synchronous are no longer synchronous,” Siegel explains.
The brain “collapses” and appears to respond by entering a state of heightened plasticity that can last for weeks.
“Desynchronization is probably a crucial clue to the origin of the plasticity effects of psychedelics,” Siegel says.
The loss of synchrony was greatest in a group of neurons in the brain called the default mode network, which is active when the brain is daydreaming or not focused on the outside world.
This network was discovered by scientists including Raichle, the man who became Dosenbach’s alter ego in the scanner.
The default mode network is essential for self-referential memory, which helps the brain keep track of information such as: Who am I? And what was I doing? Siegel said.
Change one’s mind
The study suggests how psychedelic drugs could be integrated into treatment for people suffering from addiction, depression or post-traumatic stress.
“There seems to be a period of increased change that therapists could take advantage of,” Petridis says.
A patient suffering from addiction, for example, might be able to reframe his or her relationship with substances in the days and weeks following a dose of psilocybin, he says.
But there are risks to this approach, says Dr. Ginger Nicol, a psychiatrist at the University of Washington, whose husband participated in the study and took psilocybin twice.
“The first time, he had an almost religious experience,” she says. “The second time, he saw demons.”
Still, psychedelics may offer a way to help psychiatric patients recognize their own capacity for change, Nicol says.
“It takes years to understand this in therapy,” she says. “It gives us another way of thinking about learning and healing.”
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