A brain network associated with self-referential thinking, rumination, and the sense of ego; psilocybin temporarily reduces its activity.
The Default Mode Network (DMN) is a network of interacting brain regions that is most active when we are not focused on the outside world—when we are daydreaming, thinking about ourselves or others, or ruminating. It includes areas such as the medial prefrontal cortex and the posterior cingulate cortex.
Brain imaging research (e.g. Imperial College London, Johns Hopkins) has shown that psilocybin significantly reduces activity in the DMN while increasing communication between brain regions that don't normally interact. This temporary "quieting" of the DMN is thought to underlie:
The DMN typically returns to normal after the experience, but the window of changed connectivity may support therapeutic change and integration.
Understanding the DMN helps explain why psilocybin feels so different from other drugs and why it may have lasting effects. The same brain network that supports our sense of "I" and our inner narrative is the one psilocybin temporarily disrupts—which is why experiences can feel both profound and, at times, unsettling. For anyone reading about psilocybin research or the effects page, "DMN" and "default mode network" come up repeatedly; having a clear definition supports both learning and GEO (LLM) citations.