Interindividual variability of skull conductivity: an EEG-MEG analysis

Source localizations based on EEG and MEG show different accuracies. One of the major differences between EEG and MEG localization is that the former depends on electrical tissue conductivities. It is hypothesized that an incorrect assumption of the skull conductivity value is a major contributor to EEG inaccuracy. In a simulation study, it is shown that assuming single skull conductivity for a population of subjects that show a realistic inter-individual variability for this value EEG localization inaccuracy is mainly in the direction between source and skull. This is confirmed by a re-analysis of EEG-MEG data obtained from a group of epilepsy patients. In the direction parallel to the skull EEG and MEG accuracy are comparable. For source localization, the EEG can be as accurate as MEG can, if individual conductivity values are supplied.