LSD alters brain network dynamics non-uniformly over time, making globally segregated connectivity states more complex and weakening the link between functional and anatomical connectivity. The drug reduces functional connectivity in the anterior medial prefrontal cortex specifically during states of high segregation. Ego dissolution was predicted by increased small-world organization during a state of high global integration. These temporally-specific effects reveal a more nuanced picture of psychedelic-induced changes in brain connectivity and complexity than previously reported.
Consciousness depends on how tightly brain function follows the brain's physical wiring. Using MRI scans, researchers measured structure-function coupling across spatial scales in people who were unconscious from anesthesia or brain injury and in people under psychedelics (LSD or ketamine). During loss of consciousness, function more closely tracked the brain's structural connections, a signature that could distinguish behaviorally similar brain-injured patients and detect covert consciousness. In contrast, psychedelics decoupled function from structure, and this decoupling correlated with physiological and subjective scores. The findings suggest that connectome harmonic decomposition reveals how neuromodulation and network architecture jointly shape consciousness.