Olfactory event-related potentials in psychosis-prone subjects

Previous studies in schizophrenic patients have suggested that there are changes in olfactory sensitivity. In order to externally validate a psychometrical assessment of the psychosis-risk indicated by schizotypic factors, this study was carried out to determine whether changes in olfactory perception could be determined even for persons merely at risk of developing schizophrenia. These 'psychosis-prone' subjects consistently scored high in either the scale for 'physical anhedonia' (PA) or the scale for 'perceptual aberration' (PAB). Thus, three groups were investigated (control, n = 11; PA, n = 12; PAB, n = 12). Each subject participated in one testing session where the two odorants, vanillin (pleasant) and hydrogen sulphide (unpleasant), were applied by means of a specially designed delivery apparatus. Subjects rated both the intensity and the hedonic quality of the stimuli. In addition, olfactory event-related potentials (OERP) were recorded after dichotomous stimulation. In general, there were only few significant differences between the three groups investigated. Contrary to expectations, ratings for pleasantness of vanillin were highest in PA subjects compared to PAB subjects and controls (p < 0.05). Correspondingly, OERP amplitudes in response to vanillin were largest within the PA group (p < 0.05). For hydrogen sulphide, PAB subjects showed the smallest OERP amplitudes (p < 0.05). In addition, it was observed that female subjects had significantly larger OERP amplitudes when compared to male subjects (p < 0.05), which possibly indicates gender differences in olfactory sensitivity.