Evaluation of inverse methods and head models for EEG source localization using a human skull phantom

We used a real-skull phantom head to investigate the performances of repres entative methods for EEG source localization when considering various head models. We describe several experiments using a montage with current sources locate d at multiple positions and orientations inside a human skull filled with a conductive medium. The robustness of selected methods based on distributed source models is evaluated as various solutions to the forward problem (fr om the sphere to the finite element method) are considered. Experimental results indicate that inverse methods using appropriate cortex -based source models are almost always able to locate the active source wit h excellent precision, with little or no spurious activity in close or dist ant regions, even when two sources are simultaneously active. Superior regularization schemes for solving the inverse problem can dramati cally help the estimation of sparse and focal active zones, despite signifi cant approximation of the head geometry and the conductivity properties of the head tissues. Realistic head models are necessary, though, to fit the d ata with a reasonable level of residual variance.