Computationally, the Laplacian suppresses volume-conducted contributions by eliminating the potential accounted for by the recording reference, as well as associated linear spatial trends. Because of this property, an active generator in surface cortex could also be strongly attenuated if it is broadly-distributed (e.g., diffusely synchronized). Likewise, the generators of EEG activity that is transmitted via local wave-propagation across contiguous cortical regions will also be difficult to identify using simple CSD methods if they result in traveling or standing waves (Robinson, 2003; Nunez and Srinivasan, 2006b).
