Default mode network is suppressed by meditation practice | Roland Griffiths
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Activity in the default mode network (DMN), a group of interacting brain regions implicated in self-related thinking, rumination, and depression, is suppressed by psilocybin and other psychedelic substances. Interestingly, strong evidence indicates that meditation also reduces DMN activity, likely due to its emphasis on the present and non-self-related thoughts. Teasing out the mechanisms by which psychedelics and meditation elicit their beneficial effects on the brain has proven challenging, however. In this clip, Dr. Roland Griffiths discusses similarities in the effects of psilocybin and meditation on the brain and their potential usefulness in treating depression.
Roland: There's a lot that we don't know about the nature of those experiences. There's a little bit known about the immediate effects of psilocybin. Certainly, we know that psilocybin binds serotonin 2A. We know different areas of brains that are activated and deactivated. We know something about the default mode network.
Rhonda: I wanted to ask you about that. It's very interesting.
Roland: Yeah. And so work from the UK and additional work now is showing that at least acutely, psilocybin appears to decrease activity within the default mode network.
Rhonda: So from my understanding, because I don't know much about this and this is all from neuroimaging studies you're talking about which I'm sourced in. The default mode network, is that something that's active like when you're ruminating on something, like when you're thinking about something that you...? So rumination which is associated with depression, and ruminating on the future or the past or...
Roland: Exactly.
Rhonda: That's it, right?
Roland: Yeah, that's it. And so activity in the default mode network is actually increased in depression, and here, a couple of the hubs are prefrontal cortex and posterior cingulate. And the connectivity and activity in those regions are decreased. Now, the interesting thing about the default mode network is it is associated with rumination. It's sometimes thought to be responsible for what's called self-referential processing as...
Rhonda: What's that?
Roland: Ideas that relate to a sense of self, and that's kind of what rumination is. Woe is me...yeah. So that's increased in depression, and interestingly, activity in the default mode network is decreased in long-term meditators.
Rhonda: Oh, that's interesting.
Roland: Yes, yeah. And that fits, if you think about it, with this whole story about goals of meditation being to bring you into the present moment, to drop the ego, to surrender a sense of self, if you will. So the curious thing now is that psilocybin looks very much like meditation in that regard. So that decreases in the default mode network, and that kind of fits with this story we can tell in terms of the phenomenology that one thing that people are encouraged to do when they have this experience is surrender a sense of egoic holding. That is kind of get out of the way of the experience and just be present in the present moment, and that's the thing that I...one of the qualities of that experience where you get out of past and future and your present and you're present in a way that it untangles you from this hell sense of self and constraining.
But these, of course, are all kind of words we don't have their descriptive ways of putting a framework around psychological processes, but they fall short of kind of the empirical hard science that we would like to have. So it's kind of frustrating. We're dealing a lot in metaphor at this point in terms of descriptive framework for how these experiences might affect people.
A group of interacting brain regions implicated in self-related thinking, rumination, and depression. The default mode network is typically active when a person is not focused on the outside world and the brain is at wakeful rest, such as during daydreaming and mind-wandering. Functions include autobiographical information, self-reference, emotions of one's self and others, theory of mind, moral reasoning, social evaluations, social categories, remembering past, imagining future, and story comprehension.
A mood disorder characterized by profound sadness, fatigue, altered sleep and appetite, as well as feelings of guilt or low self-worth. Depression is often accompanied by perturbations in metabolic, hormonal, and immune function. A critical element in the pathophysiology of depression is inflammation. As a result, elevated biomarkers of inflammation, including the proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, are commonly observed in depressed people. Although selective serotonin reuptake inhibitors and cognitive behavioral therapy typically form the first line of treatment for people who have depression, several non-pharmacological adjunct therapies have demonstrated effectiveness in modulating depressive symptoms, including exercise, dietary modification (especially interventions that capitalize on circadian rhythms), meditation, sauna use, and light therapy, among others.
One of the most metabolically active regions in the brain. The posterior cingulate likely integrates information in the brain, but no scientific consensus currently exists regarding its role in cognitive function. The posterior cingulate is activated during self-related thinking and deactivated during meditation. Disorders associated with the posterior cingulate include depression, Alzheimer's disease, autism, attention deficit-hyperactivity disorder, traumatic brain injury, and schizophrenia.
The area of the brain located in the front portion of the frontal lobe, just behind the area commonly known as the forehead. The prefrontal cortex is involved in a variety of higher cognitive functions and behaviors such as executive function and expression of appropriate social behavior.
A naturally occurring psychedelic compound produced by more than 200 species of mushrooms. As a prodrug, psilocybin is quickly converted by the body to psilocin, which has mind-altering effects including euphoria, visual and mental hallucinations, changes in perception, a distorted sense of time, and spiritual experiences, and can include possible adverse reactions such as nausea and panic attacks.
The practice of dwelling on external stressors to excess. Rumination can set in motion a cascade of hormonal and physiological responses that harm mental and physical health. A key player in the body’s response to rumination is a biological pathway that starts in the brain’s hypothalamus with the release of corticotrophin-releasing hormone and has a direct effect on many parts of the body including the brain, gut, and DNA. Meditation has been shown to reduce rumination and its negative effects.
A small molecule that functions as both a neurotransmitter and a hormone. Serotonin is produced in the brain and gut and facilitates the bidirectional communication between the two. It regulates many physiological functions, including sleep, appetite, mood, thermoregulation, and others. Many antidepressants are selective serotonin reuptake inhibitors (SSRIs), which work by preventing the reabsorption of serotonin, thereby increasing extracellular levels of the hormone.
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