The spatial resolution of scalp EEG

The scalp electroencephalogram (EEG) exhibits spatiotemporal dynamics refle cting synchronous dendritic activity of cortical pyramidal neurons. Recent advances in EEG acquisition and electric head modeling are improving the sp atial resolution of scalp EEG, but the skull remains an obstacle. We use le ad field theory to quantify the spatial resolution of scalp EEG, contrastin g two electrode spacings and two values of skull conductivity. We show that , without cortical constraints, 19-electrode EEG systems have optimal spati al 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 Scien ce B.V. All rights reserved.