Fig. 8: A summary model of findings in this work.

a A schematic diagram of our observations based on a range of conditions: Altered global state of consciousness associates with the hierarchical shift in cortical neural variability. Principal gradients of functional connectome in the resting brain are shown for both species. Yellow versus violet represent high versus low loadings onto the low-dimensional gradient. b Spatiotemporal dynamics can be mapped to a low-dimensional hierarchical score linking to states of consciousness. c Abnormal states of consciousness manifested by a disruption of cortical neural variability, which may indicate distorted hierarchical processing. d During vivid wakefulness, higher-order regions show disproportionately greater fluctuations, which are associated with more complex global patterns of functional integration/coordination and differentiation. Such hierarchical heterogeneity is potentially supported by spatiotemporal propagating waves and by the histaminergic system.