Figure 4 shows CSD waveforms for healthy controls and depressed patients at midline sites, with reference lines fixed at latencies corresponding to loadings peaks for factors 179, 241, 343, and 542. Although nontarget N1 and P2 are comparable for the two groups, target-related differences are distributed over time and invert along the midline from a posterior source reduction (at Pz) to an anterior source enhancement (AFz, Fz) in patients (Figure 4, column 2). However, the group difference in response to novels was quite localized, being greatest at vertex (Cz), where a prominent sink (179 ms) was followed by a source (241 ms) in both groups. Although the amplitude of the sink was comparable in the two groups, the novelty vertex source was markedly reduced in patients. The amplitude of the subsequent novelty response at frontal sites (343 ms) did not differ between groups.
