Altered sense of agency in Gilles de la Tourette Syndrome: behavioural, clinical and fMRI findings

Current neurocognitive models of motor control postulate that accurate action monitoring is crucial for a normal experience of agency-the ability to attribute the authorship of our actions and their consequences to ourselves. Recent studies demonstrated that action monitoring is impaired in Gilles de la Tourette syndrome, a movement disorder characterized by motor and vocal tics. It follows that Tourette syndrome patients may suffer from a perturbed sense of agency, the hypothesis tested in this study. To this end, we recruited 25 Tourette syndrome patients and 25 matched healthy controls in a case-control behavioural and functional magnetic resonance imaging study. As an implicit index of the sense of agency, we measured the intentional binding phenomenon, i.e., the perceived temporal compression between voluntary movements and their external consequences. We found evidence of an impaired sense of agency in Tourette syndrome patients who, as a group, did not show a significant intentional binding. The more reduced was the individual intentional binding, the more severe were the motor symptoms. Specific differences between the two groups were also observed in terms of brain activation patterns. In the healthy controls group, the magnitude of the intentional binding was associated with the activity of a premotor-parietal-cerebellar network. This relationship was not present in the Tourette syndrome group, suggesting an altered activation of the agency brain network for self-generated acts. We conclude that the less accurate action monitoring described in Tourette syndrome also involves the assessment of the consequences of actions in the outside world. We discuss that this may lead to difficulties in distinguishing external consequences produced by their own actions from the ones caused by others in Tourette syndrome patients.