Exploring the network dynamics underlying brain activity during rest

Since the mid 1990s, the intriguing dynamics of the brain at rest has been attracting a growing body of/nresearch in neuroscience. Neuroimaging studies have revealed distinct functional networks that slowly/nactivate and deactivate, pointing to the existence of an underlying network dynamics emerging/nspontaneously during rest, with specific spatial, temporal and spectral characteristics. Several/ntheoretical scenarios have been proposed and tested with the use of large-scale computational models/nof coupled brain areas. However, a mechanistic explanation that encompasses all the phenomena/nobserved in the brain during rest is still to come./nIn this review, we provide an overview of the key findings of resting-state activity covering a range of/nneuroimaging modalities including fMRI, EEG and MEG. We describe how to best define and analyze/nanatomical and functional brain networks and how unbalancing these networks may lead to problems/nwith mental health. Finally, we review existing large-scale models of resting-state dynamics in health/nand disease./nAn important common feature of resting-state models is that the emergence of resting-state/nfunctional networks is obtained when the model parameters are such that the system operates at the/nedge of a bifurcation. At this critical working point, the global network dynamics reveals correlation/npatterns that are spatially shaped by the underlying anatomical structure, leading to an optimal fit with/nthe empirical BOLD functional connectivity. However, new insights coming from recent studies,/nincluding faster oscillatory dynamics and non-stationary functional connectivity, must be taken into/naccount in future models to fully understand the network mechanisms leading to the resting-state/nactivity.The research reported herein was supported by the ERC/nAdvanced Grant DYSTRUCTURE (No. 295129), by the FET Flagship/nHuman Brain Project, by the Spanish Research Project SAF 2010-/n16085, by the CONSOLIDER-INGENIO 2010 Programme CSD2007-/n00012, by the Brain Network Recovery Group through the James S./nMcDonnell Foundation, by the FP7-ICT BrainScales, and by the/nTrygFonden Charitable Foundation