Magnetic Fields of the Cerebral Cortex

Abstract : The observed patterns over the scalp of magnetic fields evoked by visual, somatic, and auditory stimuli are analyzed to deduce the position and depth of the equivalent current dipole generating source. Expressions are developed for both sphere and half space models for the head, and graphs are presented to correct for the use of a pickup coil of finite diameter. For all three responses, the position of the generating source is deduced to lie in the corresponding primary projection area of the cortex. (Author)