Figures 4 and 5 show the CSD transformations of the ERP waveforms separately for patients and controls, comparing differences for H2S intensities and blank air (the corresponding ERPs referenced to the nose or to the average of all recording sites are shown in supplementary Figures S1–S4).1 A robust centroparietal P2 source, peaking between 500 and 800 ms, was accompanied by lateral-frontotemporal (F9/10, FT9/10, F7/8), mid-anterior (Nz, Nose), and inferior-occipital (Iz) sinks. However, these sinks differed from lateral-temporal (T7/8) and frontocentral (FC5/6) N1 sinks, which peaked between 250 and 450 ms over each hemisphere. Both N1 sink and P2 source, which directly corresponded to the N1 and P2 potentials in the OERP waveforms, and were present in both patients and controls, revealed a monotonic increase in amplitude with an increase in odor intensity, closely corresponding to our previous findings for low and high H2S concentrations (Kayser et al., 2010).
