therefore the coherence measure appears to result from a mixture of volume conduction effects and genuine source coherence. Therefore, surface Laplacian methods are the available best options to minimize the effect of volume conduction on coherence estimates. Further, according to Tenke and Kayser (2005), the simple fact that CSD provides a reference-independent (i.e., the waveforms at different electrodes are not influenced by activity at a common reference electrode) measure of EEG topographies is by itself sufficient to endorse its use over traditional qEEG measures which are reference-dependent (see Fig. 1 in Tenke and Kayser, 2005). Further, it has been empirically shown in the intracranial laminar recordings that CSD,derived from the local field potential (LFP) profile, virtually eliminates volume conduction at the spatial scales that are of interest to most in vivo LFP studies, and also improves the precision of inferences that can be made about underlying synaptic processes (Kajikawa and Schroeder, 2011). Thus, CSD methodology provides a global empirical and biophysical context for generator localization, spanning scales from cortical laminae to scalp topographies (cf. Tenke and Kayser, 2012).
