Inside magic mushrooms… inside the MRI

Imperial College, London, is learning what makes psilocybin mushrooms *trippy* – and what that means for our brains:

Professor David Nutt, from the Department of Medicine at Imperial College London, the 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.”

The function of these areas, the medial prefrontal cortex (mPFC) and the posterior cingulate cortex (PCC), is the subject of debate among neuroscientists, but the PCC is proposed to have a role in consciousness and self-identity. The mPFC is known to be hyperactive in depression, so psilocybin’s action on this area could be responsible for some antidepressant effects that have been reported. Similarly, psilocybin reduced blood flow in the hypothalamus, where blood flow is increased during cluster headaches, perhaps explaining why some sufferers have said symptoms improved under psilocybin.