Fig. 4: Sub-gamma oscillations emerge from weakly stable cluster synchronization.

a An example of the simulated signals in all 90 units plotted over 25 s, each representing a brain area from a brain parcellation template, filtered below 30 Hz to highlight the sub-gamma oscillatory activity typically detected with magnetoencephalography (MEG). Shades indicate the time points of increased power in the delta (yellow), theta (red), alpha (blue) and beta (green) frequency bands. For each frequency band, the threshold was defined as five standard deviations (STD) of the amplitude—in the same frequency bands—when no delays were considered. For the simulations, the resonant frequency, ω₀, of all units was set to 40 Hz, the conduction speed was tuned such that the average delay between units, 〈τ〉, was 3 milliseconds (ms) and the global coupling strength was set to K = 10. b The mean amplitude envelope (blue) of the filtered signals shown in (a) correlates with a Pearson’s correlation coefficient r = 0.7595 with the phase synchronization evaluated by the Kuramoto Order Parameter (orange, right y-axis).