Evidence for Deficits on Different Components of Theory of Mind in Huntington's Disease

Objective: The main aim of this study was to investigate the effects of Huntington's disease (HD) on cognitive and affective Theory of Mind (ToM) abilities. The relation of ToM performance and executive functions was also examined. Method: Eighteen HD patients, early in the course of the disease, and 18 healthy volunteers matched for age and educational levels, were given two tasks: a nonverbal cognitive ToM task assessing attribution of intentions to others and a revised version of the 'Reading the Mind in the Eyes' test, which is an affective ToM task assessing the understanding of other people's mental states from their eyes. Participants were also given various executive tests. Results: The two ToM tasks revealed a significant impairment of ToM abilities in HD patients. Executive functioning was impaired in the HD group and ToM performance on the attribution of intentions task was dependent on several executive processes. Conclusions: Our results are consistent with the idea that both cognitive and affective aspects of ToM could be impaired in HD patients, indicating that cortico-subcortical circuits are underlying higher social functions such as ToM. The results are also consistent with the idea that only a few executive mechanisms regulate the ToM abilities we tested in this work. They also provide a basis for the understanding of the disorganized behavior and the breakdown of interpersonal relationships in daily life after HD.