Figure 1 and 2 compare the grand mean CSD waveforms of patients and controls at all 67 recording sites for words and faces (averaged across condition), respectively.3 As one would expect for visual stimuli, the pattern of sink (negative) and source (positive) activity was most pronounced over posterior regions, and closely matched the stimulus-locked visual CSD component structure previously observed for words (Kayser et al., 2009). Distinct CSD components included inferior lateral-parietal P1 sources (approximate peak latency 80 ms at PO7 in controls) and left-lateralized N1 sinks (145 ms at P7), followed by an occipital P2 source (225 ms at O1), a central N2 sink (295 ms at FCz), and mid-parietal P3 sources (645 ms at Pz). As in our previous studies using visual stimuli (e.g., cf. Kayser et al., 1999, 2003, 2007, 2009), the P3 source was overlapped by a relative negativity at about 650 ms, which had a posterior topography, likely corresponding to a secondary N1 prompted by the stimulus offset (500 ms exposure time); however, this phenomenon did not differentially affect the experimental conditions.
