The present study soundly replicates our previous olfactory ERP findings using a combined CSD-PCA approach (Kayser et al., 2010), and underscores the value of reference-free techniques for a comprehensive description of surface potentials (Kayser & Tenke, 2010; Tenke & Kayser, 2012). Despite the widely held concern that CSDs may preferentially highlight superficial cortical sources at the expense of deep contributions (Nunez & Srinivasan, 2006, p. 333), such as those stemming from putative generators in basal cortical regions, N1 sink and P2 source clearly reflected olfactory stimulation. This parallels prior findings demonstrating adequate, or even superior condition-sensitivity for other ‘deep-generator’ components, such as P3b (Kayser & Tenke, 2006a, 2006b; Tenke et al., 2008, 2010). The neuronal generator patterns underlying olfactory N1 and P2 are not only reliable and stable but are also closely related to odor intensity and odor detection, thereby rendering these unbiased measures suitable tools to study interindividual differences in olfactory processing. This is a necessary prerequisite for ongoing efforts for identifying endophenotypes for schizophrenia, which may aid an early intervention before the onset of psychosis (e.g., Corcoran et
