The Mirror Neuron System in Relapsing Remitting Multiple Sclerosis Patients with Low Disability

To study the visuospatial/visuoperceptive function using a mirror neuron system (MNS) based approach in multiple sclerosis (MS) patients and a healthy control group. Two task-based fMRIs (an execution task and an observation task) and one resting-fMRI were performed in a group of MS patients (n = 24) and a group of healthy controls (n = 15). The execution and observation tasks consisted of the performance or observation of the index-thumb opposition task. Statistical parametric mapping approaches were used to identify differences in the brain activity and functional connectivity (FC) of the MNS between MS patients and healthy controls. Furthermore, visuospatial and visuoperceptive evaluation was performed by a neuropsychologist on all the participants. No global differences between groups were identified when the activity during both the execution and the observation conditions was tested. Nevertheless, differences in FC maps were identified: healthy controls showed higher connectivity between the MNS regions (between the inferior parietal lobule and the inferior frontal gyrus bilaterally) than MS patients. The absence of differences between the studied groups may be the consequence of the selection of a cohort of MS patients with low disability and with no recent relapse. However, the presence of a decrease in functional connectivity within the MNS in MS patients could indicate the presence of subclinical disability in MNS functioning, not measurable by neuropsychological tests.