UC Berkeley

Disgust is an emotion that is important for basic survival, in addition to having social and moral implications. Disgust reactivity appears to be significantly impaired in behavioral variant frontotemporal dementia (bvFTD), a neurodegenerative disease that selectively affects areas of the brain that are crucial for proper emotional functioning. Caregivers have reported that some bvFTD patients pick up garbage, drink beverages found on the street, and eat out of trashcans. Recent findings from our laboratory were consistent with these anecdotal reports, and demonstrated that patients with bvFTD showed deficits in their behavioral, physiological, and self-reported responses to a disgusting stimulus (Eckart, Sturm, Miller, & Levenson, 2012). The present study sought to build upon these findings. In this study, bvFTD patients and neurologically healthy control participants had their emotional facial behavior, physiology, and self-reported emotional experience measured while viewing a disgust-eliciting film. In order to determine whether disgust was potentially a uniquely compromised emotion in this population, participants' responses to a sadness-eliciting film were also examined. In addition, the present study utilized a neurologically varied sample of participants to explore (across diagnoses) the relationship between disgust reactivity and the insula, a region of the brain thought to be important for disgust responding (e.g., Adolphs, Tranel, & Damasio, 2003). The specificity of this disgust-insula relationship was examined by also testing the associations between the insula and participants' sad film responses and the associations between additional brain regions and participants' disgust film responses.

Results supported the hypothesis of a specific disgust deficit in bvFTD. BvFTD patients exhibited diminished disgust reactivity in behavioral, physiological, and experiential domains (with the most robust deficit found in physiology), yet these patients did not differ from healthy controls in their responses to sad stimuli, suggesting that the observed disgust deficit cannot be explained by a general blunting of negative emotions. In terms of brain-behavior relationships across the neurologically varied sample, results were overall in line with expectations. Lower insular volume significantly predicted smaller disgust film responses in behavioral and experiential domains, and predicted less somatic activity in response to disgusting stimuli. The present study also found that lower insular volume was partially related to diminished sad film responses, but no additional brain regions were associated with disgust film responses. These findings suggest that the insula may be important in some ways for all emotions (Craig, 2009), but may be particularly important in disgust. The present study expands on past work, sheds light on the neural correlates of disgust, and provides additional information about areas of preserved and compromised functioning in bvFTD.