Insular atrophy and diminished disgust reactivity

Disgust is an emotion that helps us deal with potential contamination (Rozin & Fallon, 1987). It produces a distinctive facial expression (e.g., wrinkled nose) and a physiological response that is accompanied by strong visceral sensations (e.g., nausea). Given the important role that the anterior insula plays in processing and integrating visceral information (Craig, 2009), it is likely to be centrally involved in disgust. Despite this, few studies have examined the link between insular degeneration and the experience, physiology, and expression of disgust. We studied a group that was heterogeneous in terms of insular damage: 84 patients with neurodegenerative diseases (i.e., frontotemporal dementia, corticobasal syndrome, progressive supranuclear palsy, Alzheimer's disease) and 29 controls. Subjects viewed films that elicit high levels of disgust and sadness. Emotional reactivity was assessed using self-report, peripheral physiology, and facial behavior. Regional brain volumes (insula, putamen, pallidum, caudate, and amygdala) were determined from structural MRIs using the FreeSurfer method. Results indicated that smaller insular volumes were associated with reduced disgust responding in self-report and physiological reactivity, but not in facial behavior. In terms of the specificity of these findings, insular volume did not predict sadness reactivity, and disgust reactivity was not predicted by putamen, pallidum, and caudate volumes (lower self-reported disgust was associated with smaller amygdala volume). These findings underscore the central role of the insula in the experience and physiology of disgust.