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 Psychedelic drugs such as LSD and magic mushrooms can profoundly
alter the way we experience the world, but little is known about
what physically happens in the brain.
In a study published in the journal Human Brain Mapping, researchers
examined the brain effects of psilocybin, the psychedelic ingredient
in magic mushrooms, using data from brain scans of volunteers who
had been injected with the drug.
"A good way to understand how the brain works is to perturb the
system in a marked and novel way. Psychedelic drugs do precisely
this and so are powerful tools for exploring what happens in the
brain when consciousness is profoundly altered," said Dr Enzo
Tagliazucchi, who led the study at Germany's Goethe University.
Magic mushrooms grow naturally around the world and have been widely
used since ancient times for religious rites and also for
recreation.
British researchers have been exploring the potential of psilocybin
to alleviate severe forms of depression in people who don't respond
to other treatments, and obtained some positive results from
early-stage experiments.
In the United States, scientists have seen positive results in
trials using MDMA, a pure form of the party drug ecstasy, in
treating post-traumatic stress disorder.
DREAM-LIKE STATE
People who use psychedelic drugs often describe "expanded
consciousness", including vivid imagination and dream-like states.
To explore the biological basis of these experiences, Tagliazucchi's
team analyzed brain imaging data from 15 volunteers who were given
psilocybin intravenously while they lay in a functional magnetic
resonance imaging (fMRI) scanner.
The volunteers were scanned under the influence of psilocybin and
when they had been injected with a placebo, or dummy drug. The
researchers looked at fluctuations in what is called the
blood-oxygen level dependent (BOLD) signal, which tracks activity
levels in the brain.
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They found that with psilocybin, activity in the more primitive
brain network linked to emotional thinking became more pronounced,
with several parts of the network - such as the hippocampus and
anterior cingulate cortex - active at the same time. This pattern is
similar to when people are dreaming.
They also found that volunteers on psilocybin had more disjointed
and uncoordinated activity in the brain network that is linked to
high-level thinking, including self-consciousness.
"People often describe taking psilocybin as producing a dreamlike
state and our findings have, for the first time, provided a physical
representation for the experience in the brain," said Robin
Carhart-Harris of Imperial College London's department of medicine,
who also worked on the study.
"I was fascinated to see similarities between the pattern of brain
activity in a psychedelic state and the pattern of brain activity
during dream sleep, especially as both involve the primitive areas
of the brain linked to emotions and memory."
(Reporting by Kate Kelland, editing by Mark Trevelyan)
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