Collective dynamical regimes and synchronization transitions in brain networks

The cerebral cortex exhibits spontaneous activity even in the absence of any task or external stimuli. A salient aspect of this resting-state dynamics, as revealed by in vivo and in vitro measurements, is that it exhibits several patterns, including collective oscillations, emerging out of neural synchronization, as well as highly-heterogeneous outbursts of activity interspersed by periods of quiescence, called "neuronal avalanches". It has been conjectured that such a state is best described as a critical dynamical process - whose nature is still not fully understood - where scale-free avalanches of activity emerge at the edge of a phase transition. In particular, some works suggest that this is most likely a synchronization transition, separating synchronous from asynchronous phases. By investigating simplified models of coupled excitable oscillators on brain networks describing the cortex dynamics at a mesoscopic level, we discuss the possible nature of such a synchronization phase transition in structurally heterogeneous systems.