The importance of differentiating between P3 subcomponents is that they are associated with different cognitive operations and neural generators (Polich, 2007), and this could provide new information on the cognitive and neural correlates of P3 reductions in depressed patients. Although novelty P3 is generally considered to be a variant of P3a, it is paradigmatically and functionally distinct from target-related P3b. In a preliminary report using integrated window amplitudes as component measures for 31-channel, nose-referenced ERPs recorded during a binaural novelty oddball task, we observed a prominent reduction in an early, frontocentral novelty P3 for 20 depressed patients when compared to 20 healthy controls (Bruder, Kroppmann, et al., 2009; Kroppmann et al., 2006). However, reliance on conventional ERP measures posed limitations for a complete separation of novelty P3 from overlapping late positive components. The present study sought to replicate and extend these findings in an independent and substantially larger sample (N = 98; 49 depressed patients) using a denser 67-channel recording montage so as to identify and quantify the underlying scalp current generator patterns derived from reference-free CSD-PCA methodology. Findings were
