There are several limitations of this study that should be noted. First, participants responded to the odors by raising their hand. Although this is unlikely to have affected the earlier OERP components (N1 or P2), it may have interfered with the measurement of later components (cf. Kayser et al., 2007). Second, subjects were not cued as to the time of odor presentation, and there was also no control of their breathing technique (i.e., natural breathing through mouth and nose). Although this could well have increased the variability of OERP measurements, leading to overall reduced OERP amplitudes compared to controlled breathing procedures (cf. Pause et al., 1999; Thesen & Murphy, 2001), there is no reason to believe that it would have differentially affected the schizophrenia patients and healthy adults. Third, OERPs were measured only to the unpleasant smelling odor of H2S. One of the distinguishing features of olfactory stimuli is their strong affective associations and the brain regions mediating olfaction overlap with those mediating emotional processing. The extent to which deficits in OERPs in schizophrenia are related to the emotional valence
