So far we have assumed an infinite conducting medium, ignoring tissue boundaries and head geometry. The conductivity a changes abruptly at tissue boundaries, and has major effects on EEG signals recorded at the scalp. Effects on MEG are smaller, but nonzero. The "forward" problem of EEG: Given the brain current sources, compute the electric potential $ on the scalp are the locations of the measurement and reference electrodes. Since $ depends linearly on the source currents JS, linear superposition applies, and it is sufficient to compute the fields due to a single dipole at first.
Was this article helpful?