This is what your brain on drugs really looks like []

by Robert T. Gonzalez /

Scientists this week published a study that reveals what the human brain looks like under the influence of psilocybin, the hallucinogenic chemical found in magic mushrooms.

The study has turned a few heads, and raised some interesting questions. What does the human brain look like during a mushroom trip? Come to think of it, what sort of activity do scientists see in the brains of people after they smoke a joint, or once they’ve downed a few beers? Let’s take a peek at what your brain really looks like on drugs — illicit and otherwise — and what scientists stand to learn from collecting this kind of information.

The results of the mushroom study were published in this week’s Proceedings of the National Academy of Sciences, by neuropsychopharmacologist David Nutt and his team. The researchers recruited thirty people to participate in the investigation, all of whom were experienced with the use of hallucinogenic drugs. The study was designed to monitor the changes in brain activity that emerge during the transition from a normal, sober state of consciousness to one influenced by the effects of the psychedelic compound psilocybin. This was accomplished by recording subjects’ brain, both before and after the intravenous administration of 2 milligrams of psilocybin (i.e. the psilocybin was injected directly into the subject’s blood stream via a vein). Two mg of psilocybin delivered intravenously is comparable to 15mg delivered orally — what the researchers describe as “a moderate dose.”

Your Brain on Shrooms


Shown here are the effects of psilocybin that the researchers observed. Regions labeled in blue indicate a decrease in brain activity. This activity was measured via two variations of a common neuroimaging method called functional magnetic resonance imagine (or fMRI for short), which works by monitoring blood flow in the brain. (It bears mentioning that while the rest of the images of brain activation in this post were also detected via fMRI, other neuroimaging techniques do exist, includingCT scanningmagnetoencephalography, andpositron emission tomography, to name a few.)

Many people have either had or heard of mind-bending experiences attributable to psilocybin — so if you or someone you know has experimented with mushrooms, the fact that the researchers’ observations reflected adecrease in brain activity during a trip will probably strike you as odd. What’s going on here, man?

“Psychedelics are thought of as ‘mind-expanding’ drugs, so it has commonly been assumed that they work by increasing brain activity,” explained Nutt in an interview with Nature’s Mo Costandi. “Surprisingly, we found that psilocybin actually caused activity to decrease in areas that have the densest connections with other areas.”

Did you catch that? The most important thing to take away from this study isn’t the fact that brain activity decreased, it’s where the activity decreased. The greatest dips in activity were observed in regions of the brain known as the medial prefrontal cortex (mPFC) and the anterior and posterior cingulate cortices (ACC and PCC, respectively). And as if that wasn’t enough, the researchers’ findings also suggest that psilocybin takes its disabling effects one step further by disrupting connections between the mPFC and PCC.

You can think of your mPFC, PCC, and a third region of your brain called the thalamus, astransportation hubs that coordinate the flow of information throughout your brain. Decreased activity within and between the brain’s hubs, conclude Nutt and his colleagues, allows for “an unconstrained style of cognition.”

What the hell does that mean? Costandi fleshes things out for us, with a little help from Aldous Huxley :

In his 1954 book The Doors of Perception, novelist Aldous Huxley, who famously experimented with psychedelics, suggested that the drugs produce a sensory deluge by opening a “reducing valve” in the brain that normally acts to limit our perceptions.

The new findings are consistent with this idea, and with the free-energy principle of brain function developed by Karl Friston of University College London that states that the brain works by constraining our perceptual experiences so that its predictions of the world are as accurate as possible.

The observations by Nutt and his colleagues come together quite nicely with a model of “unconstrained cognition.” There is, however, one small snag: the team’s findings directly contradict those observed in previous studies.

“We have completed a number of similar studies,” explains Franz Vollenweider, a neuropsychopharmacologist at the University of Zurich in Switzerland, “and we always saw anactivation of these same areas” [emphasis added].

So why don’t the researchers’ findings match up? The short answer is: don’t know; needs more research. But that doesn’t mean we can’t hypothesize. For example, in Vollenweider’s study, test subjects were administered psilocybin orally, and their brains were imaged an hour later. In Nutt’s study, however, the psychedelic compound was administered intravenously, and the brain scans were performed immediately.

According to Keith Laws, a neuropsychologist at the University of Hertfordshire, previous studies have shown that the decreases in brain activity observed by Nutt and his colleagues are also linked to the anticipation of unpleasant experiences. Being dosed with psilocybin intravenously, muses Laws, was probably a pretty stressful experience, even for experienced drug users. “I suspect,” Laws explains, “that [Nutt and his colleagues] measured something to do with anxiety.”

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