Abstract
The relation between spontaneous and stimulated global brain activity is a fundamental problem in the understanding of brain functions. This question is investigated both theoretically and experimentally within the context of nonequilibrium fluctuation-dissipation relations. We consider the stochastic coarse-grained Wilson-Cowan model in the linear noise approximation and compare analytical results to experimental data from magnetoencephalography (MEG) of human brain. The short time behavior of the autocorrelation function for spontaneous activity is characterized by a double-exponential decay, with two characteristic times, differing by two orders of magnitude. Conversely, the response function exhibits a single exponential decay in agreement with experimental data for evoked activity under visual stimulation. Results suggest that the brain response to weak external stimuli can be predicted from the observation of spontaneous activity and pave the way to controlled experiments on the brain response under different external perturbations.
Highlights
The brain represents one of the most fascinating systems where several mechanisms at different scales are deeply intertwined, resulting in a complex behavior
We have proposed a theoretical approach to predict the relation between global spontaneous and evoked brain activity, based on the linear noise approximation of the WilsonCowan model (WCM), which allows for analytical calculations
The theoretical approach relies on two main assumptions: The model is two-dimensional and parameters are tuned to achieve balanced excitation and inhibition, which leads to the fixed point = 0
Summary
The brain represents one of the most fascinating systems where several mechanisms at different scales are deeply intertwined, resulting in a complex behavior. The relation between ongoing and stimulated activity can be addressed theoretically within the general framework of statistical physics, by means of the fluctuation-dissipation relations, connecting the spontaneous fluctuations of a system with the response function to external perturbations These relations have been extended beyond the context of standard thermodynamics, to nonequilibrium systems, such as active and biological matter [14,15,16,17,18,19]. We measure the time correlation functions of spontaneous activity in several healthy subjects, finding a temporal behavior mainly characterized by a double-exponential decay This two-timescale decay observed in experiments is in good agreement with the analytical prediction of the WCM. Appendices A, B, and C report details of the experimental procedure and of analytical calculations
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