Psilocybin decreases brain blood flow

Psychedelic drug users throughout the ages have described their experiences as mind-expanding. They might be surprised, therefore, to hear that psilocybin -- the active ingredient in magic mushrooms -- actually decreases blood flow as well as connectivity between important areas of the brain that control perception and cognition.

The same areas can be overactive in people who suffer from depression, making the drug a potential treatment option for the condition.

This study is particularly interesting, because it is the first time that psilocybin's effects have been measured with fMRI, and the first experiment involving a hallucinogenic drug and human participants in the UK for decades.

Robin Carhart-Harris at Imperial College London and colleagues recruited 30 volunteers who agreed to be injected with psilocybin and have their brain scanned using two types of fMRI.

Half of the volunteers had their blood flow measured during the resulting trip; the rest underwent a scan that measured connectivity between different regions of the brain.

"Under psilocybin you see a relative decrease in 'talk' between the hippocampus and these cortical hub regions," says Carhart-Harris. "Changes in function in the posterior cingulate in particular are associated with changes in consciousness."

Carhart-Harris presented his work at the Breaking Convention conference at the University of Kent in Canterbury, UK, last week.

Read the full article here.