The spatial resolution of scalp EEG

The scalp electroencephalogram (EEG) exhibits spatiotemporal dynamics reflecting synchronous dendritic activity of cortical pyramidal neurons. Recent advances in EEG acquisition and electric head modeling are improving the spatial resolution of scalp EEG, but the skull remains an obstacle. We use lead field theory to quantify the spatial resolution of scalp EEG, contrasting two electrode spacings and two values of skull conductivity. We show that, without cortical constraints, 19-electrode EEG systems have optimal spatial resolution near 22-37 cm(3), while 129-electrode systems have 6-8 cm(3). These results emphasize the benefits of more electrodes, but also the need for methods of measuring local skull conductivity. (C) 2001 Elsevier Science B.V. All rights reserved.