Figure 6 shows grand mean CSD waveforms for 67-channel and 31-channel studies at midline sites. In both studies, the target P3b source was largest at Pz, and the novelty vertex source was earlier and larger than the novelty source at frontal sites. Consequently, the CSD-PCA extracted factors with highly comparable loadings (Figure 7a) and factor score topographies (Figures 5 and 7b), including a prominent novelty vertex source factor unique to novels that was reduced in patients. Likewise, the response-related F – CP+ component (500) was more prominent in controls, particularly for the midline frontal sink. However, parietal P3 was more prominent for controls in the 31-channel study (Figure 6), both for targets and novels (335, Figure 7b).
