Cognitive and affective theory of mind in patients with essential tremor.

The theory of mind (ToM) 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 present study was to explore the neuropsychological correlates of cognitive and affective ToM in patients affected by essential tremor (ET). Thirty consecutive ET outpatients and 30 healthy age-, sex- and education-matched control subjects underwent tasks assessing short-term memory, verbal learning and executive functions, as well as tasks assessing "cognitive" and "affective" ToM; questionnaires evaluating behavioral disorders and quality of life were also administered. Although the two groups did not differ on demographic variables, ET patients scored worse on memory tasks, and showed more apathy and worse quality of life than controls. After covarying for mnestic, behavioral and quality of life scores, ET patients achieved significantly lower scores than controls on task assessing cognitive ToM, whereas no difference was found between the two groups on task assessing affective ToM. In ET, "Cognitive" ToM was significantly associated with frontal tasks, whereas "Affective" ToM was not correlated with cognitive, behavioral or quality of life scales. Our results indicate that cognitive aspects of ToM may be selectively impaired in ET. Possible underlying neural mechanisms of the deficits are discussed.