Rapid Compensation for Noisy Voluntary Movements in Adults with Primary Tic Disorders

Area of Science:

• Neuroscience
• Movement Disorders
• Sensorimotor Control

Background:

• Primary tic disorders (PTD), including Tourette syndrome, may involve sensorimotor noise affecting voluntary movements.
• Despite potential noise, patients with PTD often display normal everyday motor precision, suggesting compensatory strategies.
• Understanding this noise is crucial for characterizing PTD pathophysiology.

Purpose of the Study:

• To reveal the impact of heightened sensorimotor noise on voluntary movement variability in PTD patients.
• To differentiate between task-relevant and less task-relevant movement variability in PTD.
• To investigate the temporal adaptation of movement variability to changing task demands in PTD.

Main Methods:

• A reaching task was employed with 30 PTD patients and 30 controls, manipulating target shapes to vary task-relevant dimensions.
• Movement variability was decomposed into task-relevant and less task-relevant components.
• Alternating task blocks assessed the dynamics of adjusting movement variability to changing demands.

Main Results:

• Both PTD patients and controls accurately performed the reaching task and adjusted precision based on target shape.
• PTD patients initially showed increased movement variability when task-relevant dimensions changed, compared to controls.
• This heightened variability in PTD patients resolved over several trials, indicating rapid compensation rather than novelty or learning effects.

Conclusions:

• Individuals with PTD generate more variable voluntary movements than controls.
• PTD patients demonstrate a capacity for rapid, adaptive compensation of movement variability based on task requirements.
• These findings support the sensorimotor noise hypothesis in PTD and highlight adaptive mechanisms.