Tuesday, May 15, 2018

Psychedelics and the default mode network (DMN)

If the ego can be said to have an address, it would probably be in something called the default mode network, a high-level hub in the brain linking the frontal cortex to older centers of memory and emotion. The D.M.N. appears to be involved in a range of operations related to our sense of self, like rumination, time travel (contemplating the past and future), theory of mind (the ability to impute mental states to others) and the so-called autobiographical self: It helps us integrate whatever’s happening to us now with the story of who we are, thereby giving us an abiding sense of a self that is consistent over time. Neuroscientists recently began imaging the brains of people on psilocybin or LSD, and they were surprised to find that, rather than increasing brain activity, as you might expect, the drugs radically quieted traffic in the D.M.N. In particular, when volunteers report the experience of ego dissolution, their brain imaging shows a precipitous drop in D.M.N. activity.

Taking this network temporarily offline may allow the whole system to “reboot,” in the words of Robin Carhart-Harris, a pioneering neuroscientist who has done extensive work imaging tripping brains at Imperial College London. The “loosening of cognition” that results, he says, is especially helpful to people suffering from the varieties of mental stuckness, including depression, addiction, anxiety and obsession.

All these conditions, as Alison Gopnik, a professor of psychology at Berkeley, points out, may share an etiology. “There are a range of difficulties and pathologies in adults, like depression, that are connected with the phenomenology of rumination, and an excessively narrow, ego-based focus,” says Gopnik, whose research explores the consciousness of children, which she believes bears a similarity to psychedelic consciousness. “You get stuck on the same thing, you can’t escape, you become obsessive, perhaps addictive. It seems plausible to me that psychedelic experience could help get us out of those states, create an opportunity in which the old stories of who we are might be rewritten.”

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