Drugs such as psilocybin, the active ingredient in magic mushrooms, play all kinds of tricks on the mind. They distort the perception of time, space, and self, and even untether way. Some researchers thought that these strange effects may result from drugs excite the brain. But the first study to use functional magnetic resonance imaging (fMRI) to examine brain activity in people who took psilocybin estimated that the drug reduced the neural firing in key communication centers, essentially disconnecting some brain regions from each other.
In Central America and elsewhere, hallucinogenic drugs have been used for centuries in healing and religious ceremonies. Recent years have seen a renewed interest to exploit to explore the neural basis of spirituality and potentially to treat depression, anxiety and other mental illnesses. Yet neuroscientists know little about how these compounds act on the brain to cause such experiences intensely altered. hallucinogenic drugs are tightly regulated, and some previous studies have attempted to assess their effects on the human brain. A study using positron emission tomography (PET) revealed that psilocybin increases the metabolism of the brain, especially in the frontal cortex.
In the new work, published this week in the Proceedings of the National Academy of Sciences , researchers led by psychopharmacologists Robin Carhart-Harris and David Nutt of Imperial College London used a different method, fMRI to scan the brains of 30 people who were under the influence of psilocybin. Tight spaces and loud noises scanner could be scary for someone on psilocybin, said Nutt. To minimize the chances of anyone having a bad trip, the researchers recruited people who had taken hallucinogens before, and they handed intravenous drugs so that he would have a more rapid effect than short by example, eating magic mushrooms.
The researchers performed two types of MRI, which measures blood flow in the brain and determined that blood oxygenation, which neuroscientists generally assume is an indicator of neuronal activity. Contrary to the previous study, the analyzes showed that psilocybin reduces blood flow and neural activity in several brain regions, including the posterior cingulate cortex and medial prefrontal cortex. The researchers interviewed volunteers after psilocybin was gone and found that those in which these regions have been the most inhibited tend to report more intense hallucinatory experiences. Nutt says he is not sure why the results differ from the PET study, but speculates that this could be due to the different time during the injectable drugs and his team used oral tablets used in other research .
the posterior cingulate and medial prefrontal cortex are hubs in the so-called default mode network, a network of interconnected brain regions that become active when people let their minds wander. Some researchers have suggested that the default mode network is crucial for the introspective thought and even to generate a sense of awareness, and Nutt thinks the finding that psilocybin inhibits this network could help explain the surreal experiences causes of drug . "What I think is happening is that this network in the brain that brings a sense of self becomes less active," he said, "and you get this fragmented or dissipated sense of being."
"It is a very interesting study which raises many new questions," says Roland Griffiths, a psychopharmacologist at Johns Hopkins University in Baltimore, Maryland. He said the possibility that the drugs work by interfering with the default mode network is an attractive hypothesis that deserves further investigation.
Nutt and Griffiths are interested in the therapeutic potential of hallucinogenic drugs. Griffiths is involved in a pilot study to test whether psilocybin and psychotherapy can relieve anxiety of end of life of cancer patients. the group Nutt is looking into using the drug to treat depression, and this week the British Journal of Psychiatry he and his colleagues report that psilocybin can increase neural activity in brain regions related to memory when people remember events from their past. The drug also improved the ability of people to access personal memories and associated emotions, the researchers say can be useful in psychotherapy.
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