Motor Inhibition and Basal Ganglia: what can we learn from Parkinson’s disease?

Details

Supervisors

Duque, Julie ; Wilhelm, Emmanuelle

Faculty

Faculté des sciences de la motricité

Degree label

Master [60] en kinésithérapie et réadaptation

Abstract

By applying transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) during reaction time (RT) tasks, many studies have revealed a suppression of motor-evoked potentials (MEPs) during action preparation – a phenomenon referred to as preparatory suppression. Intriguingly, little is known about the neural structures at the origin of this suppression. The subthalamic nucleus (STN) has a strong inhibitory influence on M1 and thus represents a plausible candidate for contributing to the generation of preparatory suppression. Here, we investigated the functional contribution of the STN to preparatory suppression by probing MEPs during action preparation in Parkinson’s disease (PD) patients treated with deep brain stimulation (DBS). PD patients and matched healthy subjects participated in the study, during which they had to perform an instructed-delay choice RT task. TMS was applied over both M1 using a double coil method, eliciting concurrent MEPs in right and left index finger muscles. Pulses were applied either at rest or while participants were preparing their movement. The patients realized the task either OFF- or ON-DBS on two consecutive days, allowing us to probe preparatory suppression in PD patients, and to examine the impact of the perturbation of STN activity (ON-DBS) on preparatory suppression. Our results confirm the presence of preparatory suppression in healthy subjects. However, our observations suggest an alteration of preparatory suppression in PD patients, which does not seem dependent on the activity of the STN. Data acquisition is still ongoing and additional analyses will be needed to shed more light on these preliminary results.