Differential deficits in expression recognition in gene-carriers and patients with Huntington's disease.

Previous studies in symptomatic patients and asymptomatic gene-carriers of Huntington's disease (HD) reported a differential deficit in the recognition of facial expressions of disgust. This impairment may point to involvement of the basal ganglia in the recognition of disgust. In this study, we compared the performance of 20 patients with symptoms of HD, 20 gene-carriers of HD and 20 healthy controls on two tests of facial expressions in order to further investigate the role of the basal ganglia in disgust recognition. Recognition of fear, rather than disgust, was most severely impaired in the patients, who were also impaired at recognising expressions of anger, disgust and sadness. Direct testing for a differential deficit in disgust at the group level (and at the level of individual HD cases) revealed that the patients were in fact significantly more impaired on the other negative expressions than on disgust. The gene-carriers were not impaired on any expression, although there was a trend for the gene-carriers to be poorer at recognising fearful faces than the controls. We argue that the expression recognition performance of the patients and gene-carriers simply reflects differences in task difficulty, rather than dysfunction of any mechanisms dedicated to specific emotions. In contrast to previous studies in patients or gene-carriers of HD, our findings provide no evidence for a role of the basal ganglia in the recognition of disgust and cast doubt on whether results from HD patients and gene-carriers can be used in support of a double dissociation between recognition of disgust and fear.