Sensor density and head surface coverage in EEG source localization

In research with electroencephalographic (EEG) measures, it is useful to identify the sources underlying the potentials recorded at the head surface in order to relate the EEG potentials to brain function. The EEG recorded at the head surface is a function of how current at specific brain (primarily cortical) locations propagates through the conducting volume of head tissues. The accuracy of source localization depends on a sufficient sampling of the surface potential field, an accurate estimation of the conducting volume (head model), and the inverse technique. The present paper reports the effect of spatial sampling of the potential field at the head surface, in terms of both sensor density and coverage of the inferior (lower) as well as superior (upper) head regions. Several inverse methods are examined, using the four shells spherical head model and the finite difference model. Consistent with previous research, greater sensor density improves source localization accuracy. In addition, across all sampling density and inverse methods, sampling across the whole head surface improves the accuracy of source estimates.