UC Berkeley

In the engagement of the brain with its environment, large-scale neural interactions in brain dynamics create a mesoscopic order parameter, which is evaluated by measuring brain waves (electrocorticogram, ECoG). Such large-scale interactions emerge from the background activity of the brain that is sustained by mutual excitation in cortical populations and manifest in spatiotemporal patterns of neural activity. Band pass filtering reveals beats in ECoG power that recur at theta rates (3 −7 Hz) as null spikes in log10 power. The order parameter transiently approaches zero, and the microscopic activity is both disordered and symmetric. As the null spikes terminate, the order parameter resurges and imposes a mesoscopic spatial pattern of ECoG amplitude modulation that then governs the microscopic gamma activity and retrieves the memory of a stimulus. The brain waves reveal a spatial pattern of phase modulation in the form of a cone. The dissipative many-body model of brain dynamics describes these phase cones as vortices, which are initiated by the null spikes, and which stabilize the amplitude modulated patterns embedded in the turbulent neural noise from which they emerge.