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This publication-based thesis aims at investigating Theory of Mind (ToM) abilities in patients with basal ganglia disorders. The ToM concept refers to the ability to infer other peoples mental states such as desires, intentions or emotions (Frith & Frith, 1999). Therefore, ToM is a sophisticated human ability forming an essential requirement in human social interaction (Adolphs, 1999). ToM is conceptualized as an „umbrella term“ (Hynes, Baird et al., 2006). On the one hand, it entails affective, emotional processes, often referred to by the term empathy, which signify the emotional appreciation of the others emotional state. On the other hand, ToM entails cognitive processes (mental perspective taking) which comprise a more rational and explicit inferring of the speaker’s mental states (Decety & Jackson, 2004, Shamay-Tsoory, Aharon-Peretz et al., 2009).
First, the data of ToM deficits in various basal ganglia disorders is reviewed and linked to neuropsychological, neuroanatomical and neurophysiological arguments accounting for the basal ganglias involvement in ToM processes (study 1). Furthermore, two studies invest-tigate affective and cognitive ToM abilities in patients suffering from basal ganglia disorders. In study 2, the examination of patients suffering from Parkinson’s disease (PD) shows patients impairments in affective as well as cognitive ToM. PD patients possibly first develop deficits in cognitive ToM which are followed by reduced affective ToM abilities in the course of the disease. Study 3 investigates ToM abilities in patients suffering from Restless Legs Syndrome (RLS). This study differentiates between patients who receive dopaminergic medication and those who do not. Only those patients receiving dopaminergic substitution therapy score lower than healthy controls in affective ToM tasks. Study 4 examines neural correlates of affective as well as cognitive ToM using fMRI. Additionally, it shows neural activation in basal ganglia structures during the ToM task.
In summary, these results lead to the conclusion of basal ganglia involvement in ToM processes. ToM deficits seem to be common in basal ganglia disorders. Similar results were found in study 2, which reports difficulties of PD patients in affective as well as cognitive ToM tasks. In addition, patients suffering from RLS scored lower in affective ToM tasks, although this is only true for those patients receiving dopaminergic substitution therapy. Finally, the assumption of basal ganglia contribution to social cognitive processes like ToM is further supported by the results of the fMRI study which shows neural activation in basal ganglia structures during processing of the ToM task.