Development of high-resolution EEG devices

In this paper, we describe a new direction in the advancement of dense-array EEG technology. It is generally accepted that three-dimensional spatial analysis of EEG via electric head models requires accurate representation of both head geometry and head tissue conductivity. Anatomical information can be obtained from structural MRI. At present, however, most researchers still take conductivity parameters from standard references, despite the large variability in the available data. We have therefore developed a method for estimating regional head tissue conductivities in vivo, by injecting small (1–10 μA) currents into the head, and measuring the electric potential at the remaining electrodes of a dense-array EEG net. Despite the obvious fact that most current is shunted through the scalp, our results demonstrate that regional head tissue conductivities can be estimated to within a few percent error.