Consciousness is linked to how neural activity shifts along a unimodal-transmodal cortical axis, a simple signature that is abnormally elevated under psychedelics and in psychosis. This hierarchical dynamic reflects changes in global brain integration and connectome diversity. Quasi-periodic patterns show hierarchical heterogeneity as spatiotemporally propagating waves tied to arousal, a pattern also seen in macaques. The spatial distribution of the principal cortical gradient aligns with genetic transcription of the histaminergic system and functional connectome mapping of the tuberomammillary nucleus, which promotes wakefulness. Combining behavioral, neuroimaging, electrophysiological, and transcriptomic evidence, the authors propose that global consciousness is supported by efficient hierarchical processing along a low-dimensional macroscale gradient.
During dexmedetomidine-induced sedation, the brain's functional networks become more fragmented and dynamic, with increased switching rates and decreased integration compared to wakefulness; these changes largely reverse upon recovery of consciousness. The study tracked dynamic network reconfiguration using fMRI data from 21 healthy subjects and multilayer network analysis, comparing wakefulness, sedation, and recovery states. The findings suggest that altered states of consciousness involve a whole-brain pattern of higher modular dynamics and more fragmented communication, offering insights into the neural basis of consciousness and potential clinical relevance for disorders of consciousness.