Mapping grip-force related brain activity after a fatiguing motor task in multiple sclerosis

Area of Science:

• Neuroscience
• Motor Control
• Medical Imaging

Background:

• Motor fatigue is a prevalent yet poorly understood symptom in multiple sclerosis (MS).
• The underlying pathophysiology of motor fatigue in MS requires further investigation.
• Functional magnetic resonance imaging (fMRI) can elucidate changes in motor system activity due to fatigue.

Purpose of the Study:

• To investigate how acute motor fatigue induction alters functional activity within the motor system.
• To determine the relationship between these activity changes and the experience of motor fatigue.
• To compare brain activity patterns between MS patients and healthy controls during fatiguing tasks.

Main Methods:

• Forty-four patients with relapsing-remitting MS and 25 healthy controls performed a maximal tonic precision grip task until fatigue.
• fMRI at 3T was used to map task-related brain activity before and after the fatiguing task.
• Statistical parametric mapping analyzed changes in activation from pre-fatigue to recovery phases.

Main Results:

• Task performance was impaired post-fatigue in both groups, with increased ipsilateral primary motor hand area activation.
• MS patients exhibited bilateral increases in middle putamen and lateral prefrontal cortex activity during recovery.
• Greater recruitment of the left dorsal premotor cortex correlated with reduced self-reported daily motor fatigue in MS patients.

Conclusions:

• Multiple sclerosis patients demonstrate heightened functional engagement of the cortico-basal ganglia loop after motor fatigue.
• This enhanced activity may indicate increased cognitive effort required for movement post-fatigue.
• Recruitment of the contralateral dorsal premotor cortex appears to be a protective mechanism against daily motor fatigue in MS.