Emotional processing in Huntington´s disease: an fMRI investigation

Findings on affect recognition deficits in Huntington`s disease (HD) have been inconsistent. It is still not clear whether HD patients are afflicted by a specific deficit in the recognition of facial disgust expressions. Moreover, it has hardly been investigated if deficits in emotion recognition extend to the area of emotion experience. Therefore, we applied a new paradigm, where 28 HD patients were asked to judge facial expressions according to the displayed intensity of six basic emotions. Also, affective scenes had to be rated according to the intensity of elicited basic emotions. Relative to 28 matched controls, HD patients gave lower intensity ratings for facial expressions of anger, disgust and surprise. Moreover, the patients misclassified similar-looking facial expressions: fear was confused with surprise and disgust with anger. Thus, disgust was the only emotion with a quantitative (reduced intensity) as well as a qualitative (misclassification as anger) recognition deficit in HD patients. The ratings of the affective scenes and self-reports on emotional traits were comparable in both groups. Presentation of neutral facial expressions and scenes led to higher intensity estimations for displayed respectively perceived happiness in HD patients compared to controls. Abnormalities in grey matter volumes in specific brain regions (ROIs) were correlated with emotion recognition deficits in the HD group and affected disgusted faces (correlation with bilateral volume loss of insula and hippocampus and also right amygdale) and angry facial expression (association with degeneration of right insula as well as pre- and postcentral gyrus). Therefore, a follow-up study with functional magnetic resonance imaging seems promising, where 17 HD patients and 17 healthy controls (estimation of sample sizes by reference to previous studies using G-power) are presented with affective facial expressions and scenes. Relative to healthy individuals, HD patients should display reduced activity in specific regions of interest (ROIs; e.g. insula, amygdala) while processing affective mimic. In contrast, brain activity during the experience of basic emotions should be comparable in both groups. Furthermore, during the follow-up we plan to increase the sample size of asymptomatic gene-carriers to examine if emotion processing deficits before symptom manifestation are different from those after manifestation. We also plan to increase the sample size of moderately impaired (stage 2) HD patients to investigate how emotion processing deficits are associated with course of disease.

Huntingtons disease (HD) and Parkinsons disease (PD) are both neurodegenerative motor disorders of different etiology which are both associated with basal ganglia dysfunction. A specific non-motor impairment in both disorders concerns dysfunctional emotion processing. We investigated affective traits, facial emotion recognition and emotion experience in HD and PD patients with mild to moderate disease severity. Matched healthy controls (CG) were tested for comparison. Participants answered different trait scales and were presented with pictures of affective faces which were to rate according to intensity and classification, and with emotion-eliciting scenes, where participants should rate perceived intensity. Alterations of the patients brain gray matter volume and brain activation were measured using a 3 Tesla Siemens TrioTim scanner. PD patients had problems in controlling anger and disgust, pointing to difficulties with the regulation of negative emotions. Lower disgust control in PD was associated with lower functioning in everyday life and a lower capacity to recognize angry faces. Furthermore, patients with PD reported lower disgust towards spoiled food and poor hygiene, which could be related to olfactory dysfunction, one of the early signs in PD. This assumption is supported by reduction of gray matter volume in the central olfactory system, which was negatively associated with olfactory-related disgust propensity. HD and PD patients differed strongly in the recognition of facial emotions. PD patients and the CG subjects displayed comparable facial emotion decoding accuracy and similar brain activation. However, PD patients showed a stronger recruitment of somatosensory regions when looking at affective faces. It can be assumed that PD patients use increased activation of these regions as a compensatory mechanism. By contrast, HD patients showed lowered capacity in decoding angry and disgusted faces. Recognition deficits were related to regional gray matter atrophy in emotion-relevant areas as well as in memory-relevant areas. Our data point to a more severe emotion processing deficit in HD, which is difficult to compensate even in earlier disease stages. However, emotion experience was intact in both clinical groups. Disease severity was related to affective states and traits. In PD disease duration was negatively associated to capacity of emotion recognition and anger control, and motor impairment was negatively associated to disgust control and positively related to trait anxiety. In HD motor impairment was negatively associated to disgust propensity towards poor hygiene and to disgust recognition. This indicates that with disease progression a worsening of social functioning must be expected in both diseases.