Ask a healthy person who’s tripped on psychedelics what it felt like, and they’ll probably tell you they saw sounds or heard colors: The crash-bang of a dropped box took on an aggressive,dark shape. A bright green light seemed to emit a piercing, high-pitched screech.
In actuality, this “cross-wiring” — synaesthesia, as it’s known scientifically — may be one example of the drug “freeing” the brain from its typical connection patterns. And this fundamental change in how the brain sends and receives information also might be the reason the drugs are so promising
as a treatment for people with mental illnesses like depression, anxiety, or addiction.
“I’m absolutely sure that, within ten years, psilocybin will be an accepted treatment for depression,” David Nutt, the director of the neuropsychopharmacology unit in the division of brain sciences at Imperial College London told me last month.
To understand why he might believe this so strongly, it helps to take a look first at how a healthy brain works — and then at how a psychedelic trip appears to modify the way a depressed brain does.
Normally, information is exchanged in the brain across various circuits, or what Paul Expert, who coauthored one of the first studies to map the
activity in the human brain on psilocybin, described to me as “informational highways.” On some highways, there’s a steady stream of traffic. On others, however, there are rarely more than a few cars on the road. Psychedelics appear to drive traffic to these underused highways, opening up dozens
of different routes and freeing up some space along the more heavily used ones.
Robin Carhart-Harris, who leads the psychedelic research arm of the Center for Neuropsychopharmacology at Imperial College London,
captured these changes in one of the first neuroimaging studies of the brain on a psychedelic trip. He presented his findings last year in New York at a conference on the therapeutic potential of psychedelics. With psilocybin, “there was a definite sense of lubrication, of freedom, of the cogs being loosened and firing in all sorts of unexpected directions,” Carhart-Harris said.
Here’s a visualization that Expert created to show the brain connections in a person on psilocybin (shrooms) — the chart on the right — compared to the connections in the brain of someone not on the drug (left):