Neuropsychological correlates of theory of mind in patients with early Parkinson's disease.

The theory of mind is the ability to attribute mental states to oneself and others and to understand that others have beliefs, desires and intentions different from one's own. The aim of the study was to explore the neuropsychological correlates of theory of mind in patients affected by early Parkinson's disease (PD). Thirty-three PD patients and 33 age-, sex-, and education-matched control subjects underwent the Frontal Assessment Battery, as well as tasks assessing "cognitive" and "affective" theory of mind, and memory abilities; questionnaires evaluating behavioral disorders and quality of life were also administrated. Although the 2 groups did not differ on neuropsychological tasks, PD patients' performance on tasks assessing cognitive and affective theory of mind was significantly worse than controls. Moreover, PD patients had more behavioral disorders and worse quality of life than controls. After covarying for behavioral and quality of life scores, the differences between patients and controls on theory of mind tasks remained significant. "Cognitive" theory of mind was associated with Frontal Assessment Battery score and 2 domains of quality of life scale, whereas "affective" theory of mind scores correlated only with behavioral scales such as the Frontal Behavioral Inventory and Apathy Evaluation Scale. The results demonstrate that both affective and cognitive aspects of theory of mind are simultaneously impaired in early PD and suggest that deficits in the 2 subcomponents of theory of mind may be linked to dysfunction of different frontosubcortical circuitries in early PD.