Neuroscientists find psychedelics may alter brain function through shifts in cortical hierarchy, challenging the idea that stronger global connectivity explains the psychedelic state

Psychedelics may alter consciousness by changing the brain's cortical hierarchy rather than simply increasing overall communication between regions. The central finding challenges a common assumption that the psychedelic state is mainly driven by more globally connected brain networks. Researchers compared brain imaging data across multiple compounds and found that classic psychedelics were linked to a flattening of hierarchical organization in the cortex. That pattern suggests sensory and higher-order regions interact differently under these drugs, with top-down constraints becoming less dominant. Ketamine appeared in the broader comparison because it can also produce altered states, helping distinguish shared versus substance-specific effects. The result matters because it points to a more precise mechanism for how psychedelic experiences arise and may refine future models of consciousness, drug action, and therapeutic effects. A hierarchy-based account could also help explain why subjective effects differ across compounds even when network-level changes appear superficially similar.