PCA and independent components analysis (ICA) have previously been used to distinguish between P3 subcomponents in the novelty oddball task. One ERP-PCA study (Strobel et al., 2004) also separated an early (240 ms) from late (324 ms) novelty P3. This study further distinguished an even later positivity (492 ms, but identified as P3b), which presumably corresponds to our late, response-related CSD-PCA factor (i.e., F – CP+). Moreover, CSD maps derived from early novelty P3 had a more posterior (i.e., central midline) topography than was obtained for the late component. Debener et al. (2005) used ICA to further explore the class of novel stimuli. They evaluated the impact of using novels as nontargets in an ongoing target detection task (in their case, silent count) by comparing the ERP response to that obtained when novels were targets. Trial-by-trial ERPs were submitted to ICA, which separated an anterior from a posterior cluster. The anterior cluster corresponded, in part, to a midline frontocentral novelty P3, whereas the posterior cluster reflected aspects of parietal P3b. As reflected in single-trial and split-half plots, nontarget novelty P3
