Brain scans of people under the influence of the psilocybin, the active ingredient in magic mushrooms,
have given scientists the most detailed picture to date of how psychedelic drugs work. The findings of two studies being published
in scientific journals this week identify areas of the brain where activity is suppressed by psilocybin and suggest that it
helps people to experience memories more vividly.
Professor David Nutt, from the Department of Medicine at Imperial College London, senior author of
both studies, said: "Psychedelics are thought of as 'mind-expanding' drugs so it has commonly been assumed that they work
by increasing brain activity, but surprisingly, we found that psilocybin actually caused activity to decrease in areas that
have the densest connections with other areas. These hubs constrain our experience of the world and keep it orderly. We now
know that deactivating these regions leads to a state in which the world is experienced as strange."
In the first study, published in Proceedings of the National Academy of Sciences (PNAS), 30 healthy
volunteers had psilocybin infused into their blood while inside magnetic resonance imaging (MRI) scanners, which measure changes
in brain activity. The scans showed that activity decreased in "hub" regions of the brain - areas that are especially well-connected
with other areas.
The second study, published online by the British Journal of Psychiatry, found that psilocybin enhanced
volunteers' recollections of personal memories, which the researchers suggest could make it useful as an adjunct to psychotherapy.
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