Brain-wide signal levels can reliably distinguish sleep and anesthesia from the awake state in human and monkey fMRI resting state data. A whole-brain computational model reproduces changes in global synchronization, functional connectivity, structure-function relationship, integration, and segregation across vigilance states. The awake brain operates near a Hopf bifurcation, which coincides with globally correlated fMRI signals. Simulated lesions of connectivity hubs in the posterior brain and subcortical nuclei disrupt the model's awake state, matching predictions from graph-theoretical analyses of structural data.
Psilocybin and the conventional antidepressant escitalopram produce opposite changes in the brain's hierarchical non-equilibrium dynamics when treating major depressive disorder. Using resting-state fMRI before and after treatment, researchers built whole-brain models and measured how much each patient's brain activity deviated from the fluctuation-dissipation theorem. Baseline measures distinguished treatment responders from non-responders within each group. The deviation from the fluctuation-dissipation theorem may serve as a marker to differentiate the brain effects of psilocybin and escitalopram, contributing to understanding how these treatments work for depression.