Despite the general comparability of CSD-PCA solutions across oddball tasks, there were notable target-related differences between components in the novelty task as compared with other oddball tasks using tonal stimuli. First, rather than overlying the lateral surface of the frontal lobes, the topography of the target-related N2 sink was largely confined to midline frontal sites. Second, the target-related P3 source included a secondary topography at the same midline frontal sites, rather than being restricted to a parietal P3b topography. These target-related characteristics presumably reflect the changed expectancies in the novelty oddball task, in which target likelihood was reduced (.12 compared to .2) and a class of novel nontargets (distracters) was added. These differential characteristics were replicable across recording systems and evident regardless of whether a low- or high-density montage was used. They cannot be attributed to false alarms, because only correct trials were included in the averaged waveforms. Task difficulty can also be ruled out, as they were not observed in a more difficult dichotic oddball task (Tenke et al., 2008). Although the novelty oddball task differed in stimulus timing
