Neural underpinnings of perception and experience of disgust in individuals with a reduced sense of smell: An fMRI study

Abstract

BackgroundIndividuals with reduced olfactory function (anosmia, hyposmia) have reported changes in disgust perception and disgust experience compared to normosmic controls. The current functional magnetic resonance imaging (fMRI) study investigated the neural underpinnings of the altered disgust processing. MethodTwenty-four patients with anosmia or hyposmia and 26 normosmic controls were presented with images depicting facial expressions and scenes from the categories disgust and neutral. The disgusting scenes depicted stimuli that typically smell repulsive (spoiled food, excrements). Brain activity and structure in the primary olfactory cortex (POC) and in a region that processes affective/motivational olfactory-related information (insula, orbitofrontal cortex, basal ganglia) were compared between the two groups. ResultsThe anosmic/hyposmic participants were characterized by greater activation in the POC while looking at disgusting scenes. The POC can be activated by olfactory imagery and holds predictive templates of olfactory stimuli. The neural processing of the facial stimuli did not differ between the two groups. Additionally, group differences in functional connectivity and brain structure were not present or only minor. ConclusionThe increased POC activation in anosmic/hyposmic patients might reflect a compensatory process that helps to compensate for their olfactory deficit. However, in general, this study identified only small adaptations in the neural disgust system as a consequence of reduced olfactory function.