An evaluation of single dipole solutions to extended sources in EEG and MEG

Interictal spikes as observed in epilepsy patients are assumed to be generated by relatively large patches of activated cortex. In order to check the validity of single dipole solutions to such spikes in EEG and MEG a simulation study is performed in a realistically shaped cortical model. It is shown that both in EEG and MEG the center of activated cortex can be misrepresented by single dipole solutions by more then 1 cm. The geometry of sulci and gyri determines where, for which modality, this effect is larger.