Cortical aperiodic ‘ clock ’ enabling phase transitions at theta rates

Brains are open thermodynamic systems, continually dissipating metabolic energy as heat in constructing spatiotemporal patterns of neural activity. Here observations on patterns of cortical oscillations are described as Prigogine’s “dissipative structures” forming at conditionally stable operating points far from equilibrium. The approach is to locate experimentally a small-signal, near-linear range in which impulse responses superpose, then to extend the analysis into nonlinear ranges by piece-wise linearization. The resulting root loci are re-interpreted as projections from a phase plane, in which the phase boundaries are plotted in terms of degree of order corresponding to volume vs. rate of energy dissipation (power) corresponding to temperature. Properties of neural microscopic activity transit across scales to macroscopic states.