Brain function as revealed by current density analysis of magnetoencephalography signals

Magnetoencephalography signals are used to extract two-dimensional estimates of the cortical current density associated with spontaneous and steady state brain activity as well as auditory and visual evoked responses. The results provide clues about the organization of the electrical activity across wide cortical regions. Similarities and differences in spontaneous and evoked responses are highlighted and related to findings from other techniques, raising the possibility that volume conduction currents may play some role in coordinating brain function across widely separated cortical regions.