How people with multiple sclerosis cope with a sustained finger motor task: A behavioural and fMRI study

Motor and non-motor basal ganglia (BG) circuits can help healthy subjects cope with task-induced central fatigue and re-establish motor performance after deterioration. This work aimed to assess whether patients with multiple sclerosis (MS) were able to recover motor performance after deterioration due to a demanding task and whether BG activity played a role in performance recovery in this population. Fourteen patients with MS performed a finger-tapping sequence with their right hand during three fMRI sessions: at baseline, after a demanding finger motor task (5-min sequence repetition) and after a short rest period. We observed deterioration of spatial and temporal accuracy with task repetition, as expected; after rest, temporal but not spatial accuracy recovered. Further, higher subjective fatigue was associated with increased motor performance deterioration and reduced temporal accuracy recovery. The amplitude of the BOLD signal change in the left caudate, putamen, globus pallidus, thalamus and amygdala was high at baseline and significantly reduced after the demanding task. Following rest, activity achieved values similar to the baseline in all these regions except for the amygdala. These findings suggest that patients were in a fatigue-like state since task beginning, as they showed enhanced BOLD signal change in the subcortical structures known to be recruited in healthy subjects only when coping with fatigue to recover motor performance. Abnormalities in motor and non-motor BG functions can contribute to fatigue in MS.