SOURCE ESTIMATION IN THE HUMAN BRAIN FROM EEG BASED ON THE SSB HEAD MODEL

Neuronal activity in the brain cortex is replaced by a small current d ipole, and hence the localized electric activities of the cortex are w ell approximated by equivalent current dipoles. Position and moments o f these equivalent dipoles are estimated from the scalp potentials. In this analysis, the head as a conductor is divided into three volumes with uniform electric conductivity: Scalp, Skull and Brain tissue; we call this head model the SSB Head Model. The boundary element method i s used in solving this problem and reliability of the final result mai nly depends on the arrangement of nodal points on the surfaces of thes e three regions for numerical calculation, the electric conductivity r atios of the three regions in the model, and the number of electrodes. By means of computer simulation we investigated dependence of errors in the estimated dipole position on these factors. It is found that ar rangement of nodal points must be decided adaptively depending on the source position.