Social reasoning in Tourette syndrome.

INTRODUCTION Tourette syndrome (TS) is thought to be associated with striatal dysfunction. Changes within frontostriatal pathways in TS could lead to changes in abilities reliant on the frontal cortex. Such abilities include executive functions and aspects of social reasoning. METHODS This study aimed to investigate executive functioning and Theory of Mind (ToM; the ability to reason about mental states, e.g., beliefs and emotions), in 18 patients with TS and 20 controls. A range of tasks involving ToM were used. These required participants to make judgements about mental states based on pictures of whole faces or the eyes alone, reason about humour in cartoons that featured sarcasm, irony or "slapstick" style humour, and make economic decisions. The executive measures assessed inhibition and verbal fluency. RESULTS Patients with TS exhibited significantly poorer performance than controls on all four tasks involving ToM, even when patients with comorbid obsessive-compulsive disorder were excluded. These difficulties were despite no inhibitory deficits. Patients with TS exhibited impairment on the verbal fluency task but their performance on executive and ToM tasks was not related. CONCLUSIONS We propose that TS is associated with changes in ToM. The observed deficits could reflect dysfunction in frontostriatal pathways involving ventromedial prefrontal cortex.