Fig. 4: Complex and dynamic brain states unveiled by global signal topology and the hierarchical index during rest.
From: Hierarchical fluctuation shapes a dynamic flow linked to states of consciousness
a Simplified diagram for dynamic GS topology analysis. b two-cluster solution of the GS topology in 9600 time windows from 100 unrelated HCP individuals. Scatter and distribution plots of the hierarchical index; the hierarchical similarity with the GS topology is shown. Each point represents a 35 s fragment. State 1 has significantly larger hierarchical index (P < 0.0001, two-sided two-sample t-test) and hierarchical similarity with GS topology (P < 0.0001, two-sided two-sample t-test) than State 2, indicating a higher level of vigilance and more association regions contributing to global fluctuations; meanwhile, the two variables are moderately correlated (r = 0.55, P < 1 × 10−100, two-sided Spearman correlation). c For a particular brain region, its connectivity entropy is characterized by the diversity in the connectivity pattern. d Left: Higher overall connectivity entropy in State 1 than State 2 (P = 1.4 × 10−71, two-sided two-sample t-test, nstate 1 = 4571, nstate 2 = 5021). Right: higher overall connectivity entropy in states with a higher hierarchical index (top 20% versus bottom 20%; P < 1 × 10−100, two-sided two-sample t-test, nhigh = 1920, nlow = 1920). *P < 0.0001. In each box plot, the midline represents the median, and its lower and upper edges represent the first and third quartiles, and whiskers represent the 1.5 × interquartile range. e, Difference in GS topology between State 1 and State 2 spatially recapitulates the principal functional gradient (r = 0.89, P < 1 × 10−100), indicating that the data-driven GS transition moves along the cortical hierarchy. f Distribution of Pearson’s correlation between the hierarchical index and mean connectivity entropy across 96 overlapping windows (24 per run) across 100 individuals. In most individuals, the hierarchical index covaried with the diversity of the connectivity patterns (mean r = 0.386). Source data are provided as a Source Data file.
