Understanding the emotional content of an event can be facilitated by the integration of information from multiple sensory modalities. In how far olfactory cues can affect the processing of emotional visual information is however unclear. The present study investigated whether olfactory primes selectively inhibit or facilitate the recognition of an emotional facial expression. Furthermore, we assessed whether emotion recognition deficits in schizophrenia could be improved by congruent crossmodal priming. In each trial, subjects were exposed to a 1.5 sec odorant airpuff followed by a facial affect recognition task. Three odorants of different valence were used: vanillin (pleasant), ambient air (neutral) and hydrogen sulphide (unpleasant) in combination with the correspondent facial expressions of happiness, neutral affect, and disgust. Each odorant and each face were combined, resulting in nine possible pairings presented in a pseudo-randomized order. For healthy subjects, we found an RT advantage for happy faces under baseline conditions, but not when an odorant prime was presented. Furthermore, there was an effect of crossmodal congruency for disgusted faces; they were recognized faster when preceded by hydrogen sulphide than by ambient air or vanillin. At baseline, accuracy was higher for neutral than for digusted faces; this effect was modulated by the olfactory primes. Preliminary data on schizophrenia patients and matched controls revealed no such RT pattern for the patient group. Furthermore, accuracy was lowest when a disgusted face was preceded by an unpleasant odor.
In conclusion, our results point to a cumulative effect of crossmodal stimulation for disgust which healthy controls are able to benefit from behaviorally. The opposite holds true for schizophrenia patients, who show decreased accuracy for the same condition. These findings point to a mechanism of evolutionary significance, which is disturbed in schizophrenia.