Emergent complex neural dynamics

Abstract

A large repertoire of spatiotemporal activity patterns in the brain is the basis for adaptive behaviour. Understanding the mechanism by which the brains hundred billion neurons and hundred trillion synapses manage to produce such a range of cortical configurations in a flexible manner remains a fundamental problem in neuroscience. One plausible solution is the involvement of universal mechanisms of emergent complex phenomena evident in dynamical systems poised near a critical point of a second-order phase transition. We review recent theoretical and empirical results supporting the notion that the brain is naturally poised near criticality, as well as its implications for better understanding of the brain.Understanding the brain is among the most challenging problems to which a physicist can be attracted. As a system with an astronomical number of elements, each one known to have plenty of nonlinearities, the brain exhibits collective dynamics that in many aspects resemble some of the classic problems well studied in statistical physics. The contradiction, and the provoking point in these notes, is that only a minority of the publications in the field today are concerned with the understanding of the brain dynamics as a collective process. To the contrary, the great majority of the work explains the brain through explicit or implicit connectionist paradigms. In our opinion there is a need to reflect and recognize to what degree these collectivist-connectionist views imply more than just a semantic difference, and that its adequate resolution holds the key to resolve some of the more puzzling questions about the brain. We review key results on emergent complex neural dynamics over the past few years. From the outset it should be noted that the intentionally provoking nature of these notes naturally induces a strong bias regarding cited publications; consequently this is neither a fair, nor historically correct, exhaustive or updated review of the relevant literature. Another cautionary note is that being a subject at the fringe of disciplines, physicists and biologists alike, will encounter boring passages on their most familiar topics. Nevertheless, for the sake of clarity, and with the forgiveness of the readers, we will proceed to (even excessively) define each issue at hand. What are the issues?Understanding human behavior and cognition requires the description of the laws of the underlying neural collective phenomena, the patterns of spatio-temporal brain activity. Formal approaches to study collective phenomena are one of the classical topics at the center of statistical physics, with recent novel and successful applications in diverse areas such as genetics, ecology, computer science, social and economic settings [1][2][3][4][5][6][7][8][9][10][11][12][13]. While in all these fields there is a clear transfer of methods and ideas from statistical physics, a similar flow has only recently started to impact neuroscience.The main issue addressed here belongs to the under the rug class of problems in the field,...

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