Proposed Renormalization Group Analysis of Nonlinear Brain Dynamics at Criticality

Abstract

Perception is characterized by the formation of spatiotemporal patterns of neural activity that embody mental categories of the material events provided by the senses. The patterns are constructed by modifications of the background activity, which is maintained and self-regulated at criticality, such that all frequencies and wavelengths coexist in neural activity, from the atomic level to the whole brain. Pattern formation depends on energy dissipation and occurs by phase transition upon the coincidence of two events, both endogenous. One event is the null spike in the Rayleigh noise, which is generated by mutual excitation and then band pass filtered by feedback inhibition. The frequency-specific drop in background amplitude enhances the signal-to-noise ratio of sensory-driven activity in each sensory sample taken by an action-perception cycle under limbic control. The other event is the sensory-selected activity from a Hebbian nerve cell assembly constituting reactivation of a memory of experience from past learning that is mobilized by the limbic system. The neural mechanisms of the phase transition that mediates perception may be subject to description in terms of a renormalization group based on systematic segmentation of the temporal spectra of various measures of brain activity.