The application of a Laplace operator to a montage of field potential waveforms does not necessarily prodecu a valid or interpretable CSD measure, a point that was implicit in Nicholson’s original derivation of the method, and emphasized by the distinctions noted by Nunez and Srinivasan (2006a). Even the defense of a one-dimensional CSD estimate for intracranial data hinges on a specific application for orthogonal penetrations through laminated tissue, leaving it open whether the reduced-dimensional solutions or conductivity simplifications required to produce Eq. 4 are universally appropriate. The suitability of a surface Laplacian as a measure of underlying current generator patterns must likewise rest on the plausibility and empirical value of the approach.
