The CSD transformations of these ERP waveforms, which eliminate reference-dependent ambiguities, are given in Figures 2 and 3, showing sink (negative) and source (positive) activity collapsed across new and old stimuli for controls and patients at each recording site.3 Distinct stimulus-locked auditory CSD components (Figure 2) included central N1 and N2 sinks (approximate peak latencies 120 and 420 ms at C3 for controls) and a central P2 source (200 ms at Cz). Lateral-parietal P3 sources (685 ms at P3, P7) were accompanied by lateral-frontal sinks (700 ms at F7, F8). Whereas early central sink activity (N1, N2) and the late lateral-posterior P3 source appeared markedly reduced in patients, the lateral-frontal sink activity was not, or was even more robust at lateral-temporal sites (e.g., see T7, T8).
