Shrooms limit brain blood flow and connections


(photo by Curecat/Wikimedia Commons)

Turn off your mind, relax, and float downstream, indeed. A new scientific study suggests that psilocybin -- the psychedelic drug found in magic mushrooms -- doesn't "turn on" parts of your brain but rather restricts blood flow and connections between the regions of the brain tied to perception and cognition. Imperial College London psychopharmacology researcher Robin Carhart-Harris presented the results of this study, in which 30 volunteers were injected with psilocybin and underwent brain scans, at last week's Breaking Convention conference on psychedelic consciousness. Interestingly, the data helps support psilocybin's potential use to treat depression. From New Scientist:
Less blood flow was seen in the brain regions known as the thalamus, the posterior cingulate and the medial prefrontal cortex. "Seeing a decrease was surprising. We thought profound experience equalled more activity, but this formula is clearly too simplistic," says Carhart-Harris. "We didn't see an increase in any regions," he says.

Decreases in connectivity were also observed, such as between the hippocampus and the posterior cingulate and medial prefrontal cortex.

"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."

Psilocybin has a similar chemical structure to serotonin – a hormone involved in regulating mood – and therefore binds to serotonin receptors on nerve cells in the brain. The drug may have therapeutic potential because the serotonin system in nerves is also a target for existing antidepressants.

"Psychedelic drug cuts brain blood flow and connections" (Thanks, Jody Radzik!)


  1. I’ve read that a number of other studies suggest psychedelics increase the activity of certain types of neurons, see the studies discussed here for example. I’d be interested to know if the results of this new study could somehow harmonize with the earlier ones or if they represent conflicting explanations.

  2. It is a brave person indeed who would volunteer to be stuffed inside an fMRI machine while on a heavy dose of psilocybin.

    I hope they were paid well for participation, that cannot have been fun.

    1. Depends on what kind of music they were playing, if any. I would have to listen to some kind of tune, so I could just lie there and zone out. If you’re claustrophobic straight, you’re going to freak out on shrooms. It amplifies things. If small spaces don’t bother you to begin with, you’d probably be ok.

  3. This makes sense – if the hypothalamus is being turned off, external experiences stop overwhelming internal experiences.

  4. Wasn’t that what Huxley wrote – that it’s a restriction of nutrients or oxygen to the brain that forces synaptic shortcuts, resulting in those symptoms? I know I read that somewhere…

  5. “If the doors of perception were cleansed every thing would appear to man as it is, infinite. For man has closed himself up, till he sees all things through narrow chinks of his cavern.”

    William Blake ‘The Marriage of Heaven and Hell’

  6. I remember reading a description of thought processes as having a certain amount of static or background noise. If that background noise was substantially reduced by the drug reduction of some brain activity then the remaining thoughts might seem to have much more clarity and therefore profundity.

  7. I don’t know brain anatomy very well but I wonder if the change in connections is an improvement, perhaps inhibiting influence from the “lizard” portion of the brain.

  8. Lies.

    I have understood everything in the world and in existence while using shrooms before, they are not harmful.

    1. just because there is decreased activity or connection seen in an MRI machine, doesn’t indicate that there is anything harmful going on. you could argue that decreased activity/connectivity means the brain is not as busy filtering information out and thus the ‘doors of perception’ are more open…

  9. Many meditation practices refer to turning off the chatter of the mind. The Buddhists refer to it as the “mind monkey”. whatever gets the job done.

  10. This isn’t that surprising, since a number of dissociative drugs (drugs which reduce the ability for different parts of the brain to communicate) are known to cause experiences similar to those of psylocibin. I think the idea is that without normal stimulation, firings appear more random, and that sometimes the different parts of the brain make up stimuli (since they depend on having stimuli to operate) in order to fill the gaps in their communication.

  11. As another shroomhead I too can state that they are completely harmless. If anyone experiences harm from it, it’s either due to some kind of preexisting mental disorder, or simple ill-preparedness to the drug that the user didn’t account for.

    Concerning the article, I think of it like this:

    Without sight, a blind person’s other senses are enhanced to make up for it.. or at least, the lack of sight allows them to focus more energy on their other senses. Thus, if shrooms “close doors” in the brain rather than “open them” (via decreased bloodflow, etc), then perhaps the brain experiences heightened senses to make up for it, or allows the user to focus more attention to other parts of the brain to account for it.

    It’s just like that visual experiment discovered by Jan Purkinje (Purkinje Lights) which, if I recall correctly, determined that the brain craves stimulation and it’ll stimulate itself when it needs to. Thus, by decreasing blood flow to your brain, I figure that you’re de-stimulating the brain, by which the brain then “overcompensates” to restimulate the brain. Thus, trippin’ balls! … Well, at least that’s what *I* think…

    1. As another shroomhead I too can state that they are completely harmless.

      Medical Dunning-Kruger?

      1. Medical Dunning-Kruger?

        Your comments are surprisingly mean-spirited at times, which is a bit strange, as I would think that the moderator’s remit would be to keep discussion at a higher level than it would normally devolve to.

        Or maybe they’re just supposed to be funny, I guess.

        1. They didn’t require me to have a cerebrectomy in order to take the job.

          How, exactly, is a shroomhead claiming that there are no ill effects any different than a drunk claiming that he’s not impaired or an alcoholic claiming that he’s got it all under control? You start to feel warm when you’re really beginning to freeze to death and you get euphoric when the altitude sickness becomes a real problem. Maybe when a self-proclaimed shroomhead announces that anyone who has ever been harmed by mushroom use must have a pre-existing mental illness, it might be a sign of decreased cognition on the shroomhead’s part rather than an objective analysis.

          1. Antinous, I think the term you were looking for is Temporal Lobe Resection, though it’s obvious what you meant.

            And thanks. That’s closer to what I wanted to/did say.

          2. Maybe when a self-proclaimed shroomhead announces that anyone who has ever been harmed by mushroom use must have a pre-existing mental illness, it might be a sign of decreased cognition on the shroomhead’s part rather than an objective analysis.

            I’m not entirely convinced. I’m a little familiar with the literature on the subject (John Halper’s 2003 meta-analysis of HPPD studies (Published in Drug and Alcohol Dependence, vol. 69) is a good place to start), and the evidence for harm caused by mushroom use is largely anecdotal, at best reinforced with fuzzy case studies: there is little clinical evidence to support it, despite the assertions is support of the belief. The objective analyses that have been performed have shown little adverse effect, if any.

            So there is little reason to think that shroomhead’s protestations are a result of reduced cognitive ability, given that the science behind it says the same thing. It could be a simple, subjective observation.

            Or shroomhead could be a raving lunatic who is totally out of touch with reality. On the Internet there’s really no way to know, but I tend to give people the benefit of the doubt where possible. Given that his version or reality matches the extant empirical studies, this seems like a reasonable place to apply that doubt.

  12. Y’all are vastly simplifying. First, there are over a dozen 5HT receptor types. Including autoreceptors thought to be involved in tryptamine effects.

    Second, inhibition means nothing. Inhibition in one place means releasing activity in another.

    Re: stick your head in an MRI whilst tripping: if properly prepared, ok. Set and setting. Hope they were given extra supplies for more enjoyable setting in a week though.

    Got Raphe nuclei?

    1. I’m not neuroscientist, so I’m only making educated assumptions. But still, I think what you said is kinda what I was getting at (albeit my statement was an oversimplification). But essentially I’m sure that’s the case: decreased effect in one place = increased effect in another.

      I’m also hoping that these kids they stuck in the MRI were cool wth shrooms and were able to relax. I mean, if they weren’t acustomed to shrooms and especially weren’t properly prepared (“set and setting” makes the difference!), it may have negatively affected the results… as perhaps their anxiety and shock of trippin’ balls would have certained skewed the results.

  13. Years ago, a friend, while talking about some recreational drug, told that I should try it because it “expanded your mind”.

    “No,” I said, holding two fists together, “this is your brain. And inside your brain,” I then held up one fist with the other hand mimicking the sphere where my two fists were, “is your mind.
    When you smoke dope, your brain gets a little smaller and so your mind feels bigger.”

    “Okay”, he replied, and stopped asking me to try dope.

    1. Yeah, I’m pretty sure that analogy is completely wrong.

      First off, consider that your “dream state” (the part of your brain that creates dreams) is always “on”, it’s just that, while awake and fully conscious, you normally can’t access it, or at least access it with the kind of intensity that you can while asleep and dreaming. Now some people, like Salvadore Dali, were able to NATURALLY access their “dream state” and with such intensity that so many great ideas some out of it. I’m sure a lot of your great ideas came while you were asleep or daydreaming, right?

      Thus, I’m sure that shrooms don’t “shrink” your brain to the degree that “normal thinking” (whatever THAT is) is suddenly “larger” than the user’s brain. Instead, shrooms simply allow you to access portions of your thinking which is normally “locked” while conscious. And just like some great ideas come while you’re asleep and dreaming or awake and daydreaming, a lot of good ideas come while you’re on shrooms and accessing that “dream state”. Better yet is that, unlike when you’re asleep, you may have a much better chance to remember what you’ve experienced on shrooms, which I figure is why people treat it as the “mind opening” experience that people say it is.

      TL;DR: Shrooms allow you to dream while being awake, and that has nothing to do with “shrinking your brain”.

      In any case, I didn’t think the article nor Boing Boing post meant to imply that anything was wrong, just that this was the method of how psilocybin functioned. Again, just as a blind man experiences hightened awareness in their other senses, a stoned mind experiences hightened awareness in many ways, undoubtedly due to the fact that parts of the brains are temporarily inhibited. This is an oversimplification but I’m sure it’s fundementally correct.

  14. For the Record: Reducing blood flow does not, by implicit definition, imply “harm” to the brain.
    In fact, one of the ways that people treat cluster headaches (a particularly painful neurovascular headache) is by reducing blood flow to the brain. This is acheived by treatments like oxygen therapy, and utilizing other forms of vasoconstrictors, including caffeine.

    The fact that, anectdotally, cluster headaches can be successfully treated with a non street dose of psylocybin mushrooms suddenly makes perfect sense in this context.

    Mother Nature’s Kitchen wins again.

  15. I think you missed the most interesting part of the article:

    Franz Vollenweider, who works in a similar field at the Psychiatric University Hospital Zurich, Switzerland, says that the immediate effects of psilocybin are not as important for clinical benefit as the longer-term effects. That’s because psilocybin increases the expression of genes and signalling proteins associated with nerve growth and connectivity, he says: “We think that the antidepressant effects of psilocybin may be due to a possible increase of factors that activate long-term neuroplasticity.

  16. The use of the terms ‘restricts’ and ‘limits’ to describe the decreased blood flow finding is very misleading. Blood flow decreases in different parts of the brain are very commonly detected in fMRI experiments in normal subjects doing normal tasks (that is, they are part of normal cortical processing), and the differences in blood flow that are detected with fMRI are very very small. The use of the terms ‘restricts’ and ‘limits’ makes it sound as if this study found that subjects were depriving their brains of needed biological resources, which is not at all the case: the stoned brain is still functioning normally, albeit with different patterns of activation. BTW the decrease in activity is not so surprising: most neurons in the brain are inhibitory, so if you want to fire more neurons, you should turn off the inhibitory neurons- since there are more of them than activating neurons, you will see a net decrease in brain activity.

  17. I don’t think the researcher is suggesting that the decrease in blood flow or connectivity in certain regions is harmful. I saw it more as insight into how this chemical may produce its psychedelic effects.

  18. Perhaps we as humans are generally far too active in our brains alone. When we take mushrooms, perhaps we have the opportunity to experience consciousness in the rest of our bodies. Turning the mind down for a while is not such a bad thing, ask those who have experienced it.

  19. I just had to comment to point out the misleading assumption in the headline. The effects of the most psychoactive chemical found in mushrooms are not equal to the effects of consuming the entire mushroom in it’s original state. Psilocybin is not mushrooms, though mushrooms contain psilocybin.

  20. @ Anon#20- I’m pretty sure the thought of that paragraph makes Timothy Leary smile as he tools around the multiverses in his ether-ufo.

  21. My friends and I took shrooms and went for a hike one gorgeous day. We we’re all having a great time frolicking around and exploring nature when I suddenly felt a great urge pulling me towards a certain area. It was up and over a large crop of rocks that encircled an area of forest floor. When I jumped down, i noticed the ground was covered in mushrooms. Take a guess on what kind. Freaky.

  22. Yeah but… Yeah but…

    Who the fuck injects psilocybin?

    Where are the comparative studies that show the effects of other forms of ingestion? And yet more studies on the effects of injecting alcohol, nicotine and caffeine?

    1. Who the fuck injects psilocybin?

      Admittedly, I don’t think I would want to, and I’ve consumed my fair share. The issue at hand though is to study dose response effects and other methods of ingestion introduce another variable, as one never really knows how much was actually introduced to the blood stream.

  23. I have read of anecdotal evidence that psilocybin can help those that suffer extreme migraines. This may confirm that further research is needed in that area.

  24. Did they find the part of the brain that becomes so receptive to Peter Gabriel’s “Passion” album while on mushrooms?

  25. A little off topic perhaps, but on of my favorite pieces of mushroom trivia that I’ve heard recently: the reason that Frank Herbert had people’s eyes turn blue from the Spice in the Dune books was that he was a real fan of the Little Children.

    [Reference: Told to Paul Stamets, who wrote about it in Mycelium Running.]

    Nothing wrong with a little temporary blood constriction, IMO.

  26. Sounds like yesterday’s news indeed.
    These researchers wouldn’t have acted all that surprised after reading Aldous Huxley’s Doors of Perception as Anon mentions in comment #5, which on top of conducting a similar (albeit less “formal”) experiment led Huxley to postulate as others had before him (Bergson) that the brain acts as a bottleneck or filter of perception and not the lense so to speak.
    A very sexy theory which ties up nicely a lot of loose ends and isn’t all that bad news come to think of it.

  27. Restricting blood flow would explain why sub-psychedelic doses of psilocybin are effective against migraines and cluster headaches.

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