Impaired Functional Connectivity Unmasked by Simple Repetitive Motor Task in Early Relapsing-Remitting Multiple Sclerosis

Background. Resting brain activity can be modulated by motor tasks to adapt to function. In multiple sclerosis (MS) patients, altered resting-state functional connectivity (RS-FC) has been reported and associated with impaired function and disability; little is known on how RS-FC is modulated by a simple repetitive motor task. Objective. To assess changes in RS-FC in early relapsing-remitting MS (RRMS) patients associated with repetitive thumb flexions (RTFs). Methods. A total of 20 right-handed patients with early RRMS and 14 healthy controls underwent a resting functional magnetic resonance imaging (fMRI) scan, before and after 25 minutes of alternate 30-s blocks of right RTF and rest. Dual-regression analysis of resting fMRI data followed the independent component analysis. Individual spatial maps of coherence between brain areas for 2 networks of interest, sensorimotor and cerebellar, were compared at the group level and correlated with measures of both clinical impairment and brain damage. Results. Significant RTF-induced differences in RS-FC were observed between groups in the cerebellar network because of increased RS-FC in patients but not in controls. In the sensorimotor network, the RS-FC after RTF increased in both groups, with no significant between-group differences. The sensorimotor and the cerebellar RS-FC were intercorrelated only in patients and only after the RTF. The sensorimotor RS-FC increase in patients correlated with structural MRI alterations. Conclusions. Our study unmasked RS-FC changes of motor-related networks occurring after a simple repetitive motor task in early RRMS patients only. Evaluation of altered RSN dynamics might prove useful for anticipating neuroplasticity and for MRI-informed neurorehabilitation.