Cortical aperiodic shutter 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 patterns of cortical oscillations are described as Prigogine´s ´dissipative structures´ formed at a conditionally stable operating point far from equilibrium. Around that point exists a small-signal, near-linear range in which pairs of impulse responses superpose. Piece-wise linearization extends analysis into nonlinear ranges. Resulting root loci are interpreted as projections from a phase plane, in which the three phase boundaries are graphed in the coordinates of rate of change in a dynamic order parameter (negentropy) on the ordinate analogous to static pressure vs. energy dissipation (power) analogous to static temperature on the abscissa. The graph reveals the neural mechanisms that implement phase transitions, which enable the limbic system to repeat the action-perception cycle at 3-7 Hz. Salient among these are null spikes (´vortices´) found in background ECoG.