The Critical Brain: Does the Mind operate at the Edge of Chaos?

The critical brain hypothesis is briefly introduced, and a number of implications regarding the functioning of the brain and the human mind are pointed out. After a brief overview of how the mind emerges from an evolving assembly of neuronal networks of various size-groups in the brain, we include a summary outline of a nontechnical nature relating to a few aspects of dynamical systems, based on which we introduce the idea of critical states, again avoiding technical discourse. Criticality in complex systems involves a close proximity between regular dynamics with an admixture of low dimensional chaos, on the one hand, and relatively high dimensional chaos on the other. The brain is supposed to operate in a dynamic state close to criticality, referred to as one 'at the edge of chaos', where it is driven toward such a state in a process of self-organized complexity, which makes possible an adaptive evolution of the neuronal networks, in response to an uncertain and continuously evolving environment. This process of self-organized complexity culminating in a near-critical state is referred to as self-organized criticality, in which there occasionally takes place a crossing through the critical state with an avalanche-like burst of neuronal activity, when the system return to the near-critical state. Correspondingly, the human mind also operates ‘at the edge of chaos’, which results in a phenomenal robustness and flexibility of the mind, both making it a highly adaptive entity in a constantly changing environment. In particular, the near-criticality of the mind is likely to be of enormous significance in inferential processes like creativity where there occurs an unconstrained exploration of the conceptual space, generating links between remote concepts, thereby resulting in a significant change in our view of the world. Criticality endows our mind with a certain universality in the manner in which we respond to significant changes in our environment---the hall-mark of such near-universal response being a characteristic slowness referred to as critical slowing down. This contrasts with the way we routinely engage in myriads of mental activities in our interactions with the world that are marked by enormous variability between individuals and a much shorter characteristic time of response. Near-criticality of the brain is of great relevance in the setting up of large scale neuronal networks by means of spontaneous neuronal activity---in particular, the default mode network, supposed to be the link between the self and non-self aspects of the mind, is likely to be a result of the spontaneous near-critical dynamics of the brain. Finally, the critical brain hypothesis is supposed to shed much light on the way the mind occasionally loses its coherence, with the resulting emergence of aberrant mental behavior. It needs to be mentioned, however, that the critical brain hypothesis is not a firmly entrenched theoretical idea in neuropsychology and is rooted more in the physical sciences than in neuroscience. However, it is certainly suggestive of fruitful insights that can illuminate large areas of neuropsychology in days to come.