which the spatial density grossly changes across the sampled scalp surface; cf. Tucker, 1993). Likewise, some localized generators may be difficult or impossible to identify if they vary across subjects with respect to bony landmarks (unless supported by imaging methods). Despite these concerns, we note from our experience with grouped data that these problems have not been apparent for standard ERP components (e.g., Kayser and Tenke, 2006 a,b) or regional EEG alpha (Tenke and Kayser, 2005; Tenke et al., 2011), both of which have yielded stable results across studies and montage densities. Moreover, the same concerns apply to the detection of localized activity by reference-dependent scalp potentials, where spatial nuances are subject to greater attenuation by volume conduction. The capacity to consistently identify CSD waveforms and topographies may be valuable even if they are shown to be quantitatively imprecise.
