Practice-dependent motor cortex plasticity is reduced in non-disabled multiple sclerosis patients.

Area of Science:

• Neuroscience
• Motor Control
• Neurorehabilitation

Background:

• Skill acquisition relies on synaptic plasticity, specifically long-term potentiation (LTP), in the primary motor cortex (M1).
• Neuroinflammation in multiple sclerosis (MS) may impair LTP, potentially hindering clinical recovery after motor tasks.
• Understanding alterations in practice-dependent plasticity is crucial for developing effective rehabilitation strategies in MS.

Purpose of the Study:

• To investigate whether practice-dependent plasticity is altered in patients with relapsing-remitting multiple sclerosis (RR-MS).
• To compare motor learning and cortical excitability changes between RR-MS patients and healthy controls.

Main Methods:

• Eighteen RR-MS patients and 18 healthy controls performed 600 index finger abductions.
• Transcranial magnetic stimulation (TMS) assessed cortical excitability, including motor evoked potentials (MEPs), before and after training.
• Kinematic variables and measures of intracortical inhibition were analyzed.

Main Results:

• Both groups showed similar improvements in movement kinematics with practice.
• RR-MS patients exhibited a smaller increase in MEP amplitude post-practice compared to controls.
• Resting motor threshold and short-interval intracortical inhibition remained unchanged by practice in both groups.

Conclusions:

• Practice-induced M1 reorganization is altered in non-disabled RR-MS patients, evidenced by impaired MEP modulation after motor learning.
• These findings indicate altered physiological mechanisms of practice-dependent plasticity in RR-MS.