The purpose of this section is to provide direct comparisons between surface potentials and surface Laplacian estimates for representative EEG measures in time and frequency domains, which are widely employed in the field and will therefore be familiar to most readers. Rather than reviewing specific findings reported in the literature, we aim to make the surface Laplacian transformation more transparent and less obscure using data recorded in our lab as convenient examples, with a focus on characteristic similarities and discrepancies in scalp distribution between surface potentials and the surface Laplacian. In this vein, we will not discuss any functional properties of these various measures, explicitly recognizing that any given measure may be employed in different cognitive paradigms, intended to serve different clinical objectives and research goals, and may be subject to interpretational discrepancies, all of which is beyond the scope of this paper. However, we note that surface Laplacian methods are ideally suited to help resolving existing controversies (e.g., Burle et al., 2015; Vidal et al., 2015).
