Synchronous fluctuation in broad-band processes and application to the electroencephalographic brain data

We propose phase-like characteristics in the broad-band process and introduce a novel wavelet-based method to analyze fluctuation in synchrony (FIS) in a wide frequency range. We demonstrate FIS between multifractal processes and a modeled dynamical system in phase transition. We then apply the idea to analyze surface scalp electroencephalographic data from normal subjects and traumatic brain-injured (TBI) patients. Our results show that FIS in normal subjects is more pronounced and exhibits more dynamic spatiotemporal patterns. Moreover, we find an intrinsic synchrony-variability relationship underlying these FIS characteristics.