Using insights from spatiotemporal PCA, Spencer et al. (2001) emphasized the importance of preserving a common nomenclature for putative ERP components based on their functional and topographic properties. Noting that novels produce both a posterior P3 and a frontal novelty P3, they concluded that the ERP topography produced to novels in any task reflects the summation of task-related contributions from each component. Inasmuch as this summation is largely due to volume conduction from anatomically distinct generators, it follows that these contributions may be better separated by CSD. We strongly concur regarding the importance of topography for component identification and further note that the sharpened topographies of CSD-PCA components allow the distinction of an earlier (factor 241) novelty vertex source from the later and less well-localized frontal and parietal P3 sources (i.e., factor 343). Although the later sources are generally identified as novelty P3 (P3a) and P3b (target P3), respectively, the time course and central topography of the earlier novelty vertex source clearly contribute to the early phase and midline topography of the novelty ERP.5 These findings are directly apparent from
