Default Mode Network
The brain network most associated with self-referential thought, rumination, and the narrating self. Psychedelics consistently suppress its activity, which may underlie experiences of self-dissolution.
The default mode network (DMN) is a set of interconnected brain regions — primarily the medial prefrontal cortex, posterior cingulate cortex, precuneus, and angular gyri — that becomes most active during self-referential thought, mind-wandering, autobiographical memory, and rest. Psilocybin, LSD, DMT, and ayahuasca reliably reduce DMN activity and weaken its internal connectivity, a finding first published by Robin Carhart-Harris and colleagues at Imperial College London in 2012. This disruption is widely proposed as the neural correlate of ego dissolution and is central to the entropic brain and REBUS theories of psychedelic action.
The default mode network (DMN) is a set of interconnected brain regions that becomes most active when the mind is at rest, reflecting on itself, and least active during focused, outward attention. It includes the medial prefrontal cortex, the posterior cingulate cortex, and the angular gyrus, all of which together form something like the brain's internal narrator: the voice that says "I," that rehearses the past, that anticipates the future, that maintains the story of who you are.
Psychedelic substances - particularly psilocybin, LSD, and DMT - consistently suppress DMN activity. Neuroimaging studies show that this suppression correlates with the subjective experience of self-boundary loosening: the sense that the edges of the self have become permeable, that the distinction between "me" and "everything else" has softened. Researchers Robin Carhart-Harris and Karl Friston proposed that this suppression temporarily dismantles the brain's predictive hierarchy, allowing sensory and emotional information to flow more freely without the usual filtering and interpretation by the self-model.
The DMN does not simply switch off during a psychedelic experience. It disintegrates as a coherent network and reconnects into new, temporary configurations. Brain regions that rarely communicate begin to exchange signals. This novel connectivity may underlie the unusual associations, metaphorical thinking, and emotional depth that people often report during these states.
What returns when the experience ends is not always identical to what was there before. Some research suggests that the DMN remains altered for days to weeks after a psychedelic session, maintaining a slightly more flexible connectivity pattern. This may be part of why therapeutic outcomes tend to persist beyond the session itself - the brain's self-maintenance system has been, at least temporarily, loosened from its habitual grooves.
Understanding the DMN does not explain what it feels like to have the self dissolve. But it offers one clear anchor: these are not random alterations. They are structured changes to the brain's most fundamental self-referential circuitry.
