Theory of mind performance in Parkinson's disease is associated with motor and cognitive functions, but not with symptom lateralization

Next to the typical motor signs, Parkinson's disease (PD) goes along with neuropsychiatric symptoms, amongst others affecting social cognition. Particularly, Theory of Mind (ToM) impairments have mostly been associated with right hemispherical brain dysfunction, so that it might prevail in patients with left dominant PD. Fourty-four PD patients, twenty-four with left and twenty with right dominant motor symptoms, engaged in the Reading the Mind in the Eyes (RME) and the Faux Pas Detection Test (FPD) to assess affective and cognitive ToM. The results were correlated with performance in further cognitive tests, and analyzed with respect to associations with the side of motor symptom dominance and severity of motor symptoms. No association of ToM performance with right hemispheric dysfunction was found. RME results were inversely correlated with motor symptom severity, while FPD performance was found to correlate with the performance in verbal fluency tasks and the overall cognitive evaluation. Affective ToM was found associated with motor symptom severity and cognitive ToM predominantly with executive function, but no effect of PD lateralization on this was identified. The results suggest that deficits in social cognition occur as a sequel of the general corticobasal pathology in PD, rather than as a result of hemisphere-specific dysfunction.