The inclusion of only a single odorant, in this case, stimuli associated with strong negative affective valence, is also a limiting factor. For example, recent evidence suggests odor-specific reductions in thresholds in CHR individuals, which may provide a key for uncovering the mechanisms underlying impaired olfactory signal transduction in psychosis (Kamath et al., 2012). At the same time, H2S stimuli have frequently been employed in ERP studies of olfactory function, the associated ERP morphology is well documented, and alternating odor intensity is comparably easy. In fact, the parametric manipulation of odor intensity (e.g., Turetsky et al., 2003a) combined with a no-odor control condition warranted conclusions that would otherwise not have been possible. Systematic variations of odor quality and intensity could provide additional insights into the arousal and valence dimensions of olfactory processing (e.g., Anderson et al., 2003; Kayser et al., 2012), and how these relate to deficits in olfactory function in schizophrenia and its prodromal state.
