Figure 4.

Emergence of enhanced spontaneous synchrony between brain regions in sleep-like simulations. Functional connectivity is assessed in wake-like (A–D) and deep sleep-like (E–H) states, by assessing Pearson correlation (A, B, E, F) and Phase-Lag Index (PLI) (C, D, G, H). Heatmaps show correlations between brain regions in terms of excitatory firing rates (A, C, E, G), whereas scatter plots of show relationships between inhibitory vs. excitatory firing rate correlations (B, D, F, H) where the dotted trace is the identity line. Inter-region correlations are increased across regions in sleep-like states (E) as compared to wake-like states (A), consistent with increased synchrony across brain regions in empirical brain imaging studies (M/EEG). Correlations across nodes are significantly larger between inhibitory firing rates than between excitatory firing rates in sleep-like dynamics [(F); Independent Student's t-test, t = −8.5, p = 2.8e − 17], but not during wake-like regimes [(B); t = −0.9, p = 0.35]. The PLI is consistently larger in sleep-like dynamics (G), unlike in wake-like dynamics where the PLI is diminished (C). Likewise, the PLI of excitatory vs inhibitory populations is significantly different during sleep-like [(H); Independent Student's t-test, t = 5, p = 4.6e − 7], but less so in wake-like [(D); t = 4.2, p = 1.8e − 5] states, altogether possibly suggesting a previously unidentified role of inhibition in the emergence of long-range synchrony in sleep-like activity.