Effect of anisotropy in estimation of brain sources and conductivities via coupled EEG and MEG

Purpose: This paper proposes an approach for the coupled EEG-MEG data analysis that takes into account the anisotropy of brain tissues and the different sensitivities of EEG and MEG measurements. Design/methodology/approach: The study is carried out by using a combination of analytical and numerical methods. In particular, where available, closed solutions are used to evaluate the numerical errors, while FEM models are used where anisotropy and geometrical characteristics make analytical solutions not applicable. Findings: The impact of tissues anisotropy on coupled EEG-MEG analysis has been assessed, and the effectiveness of an approach based on smart exploitation of different EEG and MEG sensitivity to improve sources reconstruction has been demonstrated numerically. Research limitations/implications: The analysis has been carried out using a spherical head model, and on simulated data. Practical implications: The proposed approach allows to improve the localization of equivalent sources for the description of cellular brain activity. Originality/value: The properties of objective functions used in brain sources reconstruction from EEG and MEG has been investigated taking into account tissues anisotropy in the spherical symmetric case. In addition a formulation of the joint source and tissues tensor conductivity estimation by exploiting simultaneously bioelectric and biomagnetic measurements based on the complementary sensitivity of those measurements has been presented.