EEG Simulation Accuracy: Reference Choice and Head Models Extension

— The EEG forward problem involves computing the scalp potentials at a finite set of electrode locations for a source configuration in a specified volume-conductor head model. Brain electrical activity spreads (spatially) over the whole head volume conductor. However, under certain circumstances, it is possible to limit the volume within which the study can be done, thus reducing model size. As the choice of a particular EEG reference site may show a substantial effect on the EEG, this might influence the feasibility of model size reduction. The goal of our study is to determine the best choice of the EEG reference allowing an acceptable accuracy in forward problem solution irrespective of model size reduction. In this paper we present results of a simulation study performed with 3 different reference schemes. We considered the following three EEG potential measurements: ideal monopolar (i.e., reference point at infinity), bipolar Czreferenced and bipolar referred to the linked earlobes. Data were obtained adopting realistic test head models extended to different percentages of a reference model that extends from head vertex to the chin. Results indicate a link between suitable model extension and the reference, confirming that monopolar measurements are less suitable for head model reduction. Keywords— EEG, FDM, Forward problem, Realistic head model, Reference, Volume conductor.