Fig. 13.4. Sensitivity distribution of EEG electrodes in the spherical head model. The figure illustrates the lead field current flow lines (thin solid lines), isosensitivity lines (dotted lines) and the half-sensitivity volumes (shaded region). The sensitivity distribution is in the direction of the flow lines, and its magnitude is proportional to the density of the flow lines. The lead pair are designated by small arrows at the surface of the scalp and are separated by an angle of 180°, 120°, 60°, 40°, and 20° shown at the top of each figure.