Psilocybin and the default mode network

What the network does

The default mode network is a set of brain regions most active when you're not focused on a task, daydreaming, ruminating, narrating your own life. Overactivity in this network correlates with depressive rumination.

What imaging studies show

Under psilocybin, activity within the network drops while communication between normally separate networks increases. Researchers describe this as a temporarily more flexible brain state, which may explain why long-held patterns feel newly negotiable.

Important caveat: sample sizes in this literature are small, and the model is contested. Treat it as a useful metaphor rather than a proven mechanism.