Dynamic dipole tracing of electric sources in the human brain

Abstract

Electric generators of an EEG are well approximated by a single current dipole when they are localized in the brain. The location and vector moment of this equivalent current dipole was estimated from scalp potentials measured with 16 to 32 electrodes arranged on the scalp, where the realistic head model with uniform, homogeneous electric conductivity was used for numerical calculations. The equivalent current dipole was obtained as a least-squares fit to the observed potentials with the aid of the boundary element method and the simplex method. This technique was applied to the somatosensory evoked potentials (SEP) and epileptic spikes. For SEP the current dipole was traced from the brainstem to the cortex at every 0.5 ms, and for epileptic spikes different current dipoles were found from spike to spike surrounding lesions. The effect of mental concentration was also found.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>