IN VIVO CONDUCTIVITY ESTIMATION USING SOMATOSENSORY EVOKED POTENTIALS AND CORTICAL CONSTRAINT ON THE SOURCE

A new method for in vivo conductivity estimation of head tissues is proposed, in the case of a realistic piecewise constant model. Unlike classical electrical impedance tomography methods, for which the conductivity is inferred from a current injection on the scalp, we use an evoked source inside the brain that comes from a somatosensory experiment. The resulting uncertainty with respect to the source is then balanced by strong constraints: we assume the source to be a single dipole located in the cortex, with orientation normal to the cortical surface. Using only EEG data, we are then able to estimate conductivity values, using the MUSIC method to recover the position of the source. Results on simulations show robustness to noise, and the applicability of the method is demonstrated on real data.