Diminished functional gradient of the precuneus during altered states of consciousness
bioRxiv December 17, 2024 Dian Lyu, Ram Adapa, Robin L. Carhart-Harris et al. preprint
The default mode network (DMN) and frontoparietal control network (FPCN), typically anticorrelated at rest in healthy brains, show continuous rather than absolute anatomical boundaries in the posterior precuneus. Connectivity differences along the dorsal-ventral axis follow linear slopes, forming functional gradients that exist only within each network's territory. These gradients flatten in altered states of consciousness (ASC), with the gradient magnitude similarly impaired across different ASC types, while spatial entropy differs between psychedelic and sedative states. The findings suggest the DMN and FPCN, though appearing distinct, may originate from a single integrated mechanism, and the loss of functional differentiation between them characterizes altered conscious states.