Sensorimotor Integration in Patients With Tourette Syndrome

The present study aims to investigate the mechanisms underlying the sense of agency in patients with Tourette Syndrome (TS). Previous evidence indicates that individuals with TS exhibit abnormalities in both explicit and implicit (absent intentional binding) experiences of agency. According to a recent theoretical framework, such alterations may stem from impaired sensorimotor integration - specifically, a dysfunction in the ability to combine sensory feedback with motor predictions about the consequences of one's own actions. This deficit may not only affect motor control but also the awareness of self-generated movements, thereby compromising the distinction between self-produced and externally produced actions.

To test this hypothesis, the study will employ the Force Matching Task (FMT), a well-established paradigm used to assess sensory attenuation - the reduced perception of intensity for self-generated sensations compared to externally generated ones. In this task, participants are asked to reproduce a force applied to their finger either by pressing directly with their own finger (self-generated condition) or by controlling a mechanical device (externally generated condition). In healthy individuals, self-generated forces are typically perceived as weaker due to predictive motor mechanisms. A reduced or absent sensory attenuation effect would indicate altered sensorimotor integration.

The primary aim of the study is therefore to evaluate whether patients with Tourette Syndrome show atypical sensory attenuation compared to healthy controls, as an index of altered sensorimotor integration underlying the sense of agency. The secondary aim is to examine the relationship between the degree of sensory attenuation and clinical symptom severity, to determine whether deficits in sensorimotor integration are associated with the intensity of tic expression or other clinical features of the disorder.

Inclusion criteria

For Tourette Syndrome group:

• Clinical diagnosis of Tourette Syndrome (TS) according to DSM-5 criteria
• Age between 18 and 65 years
• Ability to understand and comply with study procedures
• Written informed consent provided

For Healthy Control group:

• No current or past history of neurological or psychiatric disorders
• Age between 18 and 65 years
• Matched to the TS group for age, sex, and education level
• Ability to understand and comply with study procedures
• Written informed consent provided

Exclusion criteria

• History of significant neurological disorders (e.g., brain injury or dementia) or major psychiatric disorders (with the exception of conditions commonly associated with Tourette Syndrome, such as Obsessive-Compulsive Disorder, ADHD, depression, and anxiety);
• Failure or refusal to provide written informed consent;
• Confirmed pregnancy (self-reported) and/or breastfeeding.