P2); and (c) used randomization tests of component topographies (cf. Kayser et al., 2007) as a tool to identify regions associated with odorspecific stimulus processing (H2S vs. blank air). Following our previous developments in ERP analysis (e.g., Kayser & Tenke, 2003, 2006a, 2006b), we relied on a combined CSD-PCA approach to obtain meaningful and unique olfactory ERP component measures that are independent of the EEG recording reference and therefore have an unambiguous polarity and topography (Tenke & Kayser, 2012). Given our prior olfactory ERP findings (Kayser et al., 2010), we hypothesized that both N1 sink and P2 source would show monotonic increases in amplitude paralleling increases in odor intensity, with each component characterized by an activation topography that is significantly different from non-odor (blank air) stimulation. It was further predicted that CHR patients as a group would exhibit reductions of N1 sink and P2 source and their monotonic increases, although possibly to a lesser degree than seen for schizophrenia patients (Kayser et al., 2010).
