  Interactions by mutual excitation in neural populations in human and animal
brains create a mesoscopic order parameter that is recorded in brain waves
(electroencephalogram, EEG). Spatially and spectrally distributed oscillations
are imposed on the background activity by inhibitory feedback in the gamma
range (30-80 Hz). Beats recur at theta rates (3-7 Hz), at which the order
parameter transiently approaches zero and microscopic activity becomes
disordered. After these null spikes, the order parameter resurges and initiates
a frame bearing a mesoscopic spatial pattern of gamma amplitude modulation that
governs the microscopic activity, and that is correlated with behavior. The
brain waves also reveal a spatial pattern of phase modulation in the form of a
cone. Using the formalism of the dissipative many-body model of brain, we
describe the null spikes and the accompanying phase cones as vortices.
