Brainstem auditory evoked magnetic fields in response to stimulation with brief tone pulses

Brainstem auditory evoked magnetic fields evoked by monaural stimulation with Gaussian-modulated tone pulses were recorded in the parieto-occipital region of two normally hearing human subjects. Very small signals with an amplitude of 5-10 fT were detectable only under optimal (with respect to selection of subjects, technique of stimulation, minimization of ambient and instrumental noise level, signal processing, etc.) experimental conditions. The most important findings are that: (a) different components of the magnetic signal show maxima at different recording positions over the scalp, and (b) the magnetic equivalent of the electric wave V exhibits a polarity reversal at symmetrical positions in both hemispheres.