Impaired recognition of disgust in Huntington's disease gene carriers

Face processing and facial expression recognition were investigated in the earliest stages of Huntington's disease, by studying 40 people who presented for genetic testing. Twenty-three of these 'at risk' individuals turned out not to carry the gene for Huntington's disease (the AR- group). Seventeen were found to be gene carriers (the AR+ group); 15 from genetic testing, and two who showed signs of early stages of Huntington's disease. A number of standard tasks were used to provide background information, including recognition memory for words, picture naming, verbal fluency, and figure copying; none revealed significant differences between the AR+ and AR- groups. Face processing abilities were investigated using tests of identification of familiar (famous) faces, unfamiliar face matching, recognition memory for faces, and recognition of facial expressions of emotion. No statistically significant differences between the AR+ and AR- groups were found for any of these tests, but the AR+ group showed a borderline overall impairment in recognizing facial expressions of emotion (0.05 < P < 0.1). When recognition of each of the six basic emotions used was examined separately, only disgust was found to be significantly impaired. This highly selective deficit in the recognition of disgust was confirmed in the subgroup of 15 individuals shown by genetic testing to be Huntington's gene carriers; it was therefore found in people who were free from clinical symptoms and did not perform significantly more poorly than non-carriers on any of the background tests, on any of the other face processing tasks, and even for recognition of any other basic emotion. This points strongly to the importance of the basal ganglia in the emotion of disgust.