How do psychedelics work? This brain region may explain their effects
The claustrum seems to act as a switchboard, telling different parts of the brain when to turn on and off. But what happens when the switchboard operator steps away?
A brain scan from Fred Barrett's lab with the location of the claustrum indicated in purple. Image Credit: GBH/NOVA
Even if you’ve never used magic mushrooms, you may have heard what the experience can be like. People often hallucinate, seeing vivid colors or swirling patterns. And while not everyone has a positive experience, many users report feeling a deep sense of connection to the universe.
Now, medical researchers are exploring ways to harness magic mushrooms and other psychedelic substances to help treat mental health conditions like depression, addiction, and PTSD—sometimes with dramatic results. But what actually happens in the brain during a psychedelic experience? Fred Barrett, a neuroscientist at Johns Hopkins University, is one of the scientists trying to figure that out. His work suggests that “a brain region called the claustrum may be at the center of all of this,” he told NOVA.
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The claustrum is a set of two slight strips of gray matter–one tucked deep inside each brain hemisphere–that are connected to almost every other region of the brain. Francis Crick (of DNA fame) and neuroscientist Christof Koch suggested in 2005 that the calustrum’s position and connectedness made it a likely “conductor of consciousness.” Barrett compares it to a switchboard that tells other brain regions to turn on and off in response to changing stimuli.
Take, for example, receiving an email, he said. You might hear the telltale ding, and your claustrum would coordinate each step you take next. You would read the text using your visual cortex. Then your claustrum-as-switchboard would recruit your prefrontal cortex to decide whether to send a response. Once you make your choice, your claustrum would tell the decision-making regions in the prefrontal cortex to turn off and mobilize your language region and motor cortex so you can start typing words.
Knowing that the claustrum is crowded with receptors that psychedelics act on, Barrett and his colleagues wondered what happens to it when someone takes psilocybin, the hallucinogenic compound in magic mushrooms. In a recent study, he and his colleagues used a functional MRI machine to observe blood flow in the brain before and after 15 people took either psilocybin or a placebo. Neural activity in the claustra of study participants who took psilocybin was reduced by 15% to 30%, as if the switchboard operator had walked away.
With the big boss out to lunch, Barrett said, different regions of the brain can interact in radically different ways. “Networks that normally don’t turn on at the same time may turn on and stay on, and they begin to fight for control,” Barrett said. “And other brain networks that would normally be involved in emotions or memories are firing on and off in an unpredictable fashion.”
Watch: How Psychedelics Change the Brain
With the claustrum turned down, Barrett said, his team has also noticed that a network of regions called the default mode network can go quiet as well. This network is active when we think about ourselves, so its dawdling may contribute to the feeling of egolessness that so many psychedelics users report. Research has shown that people who struggle with depression, anxiety, or other mental health conditions have difficulty recovering in part because their default mode networks are stuck in a rut—that “default” setting—which can include a powerful cycle of repetitive, negative thoughts and behaviors that only get stronger as they replay.
But the sudden upheaval wrought by the claustrum’s mushroom-induced coffee break seems to have the potential to jolt the brain out of this cycle. “It may be that in this state, the normal repetitive thoughts that are baked into some neural circuits after years and years of use become less strong,” Barrett said. That may leave room for other, usually quieter circuits to have a say.
He compares the situation to a theater production in which the director suddenly leaves. The actors don’t know what to do, so they just keep saying their lines, sometimes all at once or out of order. “You may come out with a performance that is just completely disorganized,” he said. “Or you may come out with a performance that’s rearranged in a very interesting way that nobody had thought of before.” Barrett points to this dynamic as one reason psychedelic therapy may have so much potential to treat mental health conditions. In normal talk therapy, “you’re battling the circuitry that you’ve built up over a long period of time,” he says—instead of radically reorganizing it.
The profound transformations some study participants have experienced through psychedelic-assisted therapy may be possible because when the claustrum’s control is disrupted, the brain becomes more “plastic,” or flexible and open to change, Barrett said. Plasticity may be key to at least allowing that growth to happen, but it’s only the first step.
“Simply making the brain more plastic itself doesn’t necessarily always lead to a positive outcome,” he added. A controlled environment with trained therapists to guide and support the person during and after the experience is crucial to promoting that plasticity, “which can lead to learning, which can lead to healing and growth.”
Watch: Can Psychedelics Cure?
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