Increased Visual Response Delay Impact on Sensorimotor Control in Persons with Multiple Sclerosis

Multiple Sclerosis negatively affects hand function in 60% of cases. Upper extremity dysfunction in persons with Multiple Sclerosis (PwMS) has previously been linked to slower, more variable movement, increased visual response delays (Tv), and neuroimaging evidence of altered functional connectivity; yet no one knows how these aspects relate to each other. This work combines clinical, kinematic, sensorimotor control, and neural imaging techniques to gain a more complete understanding of how upper extremity dysfunction arises in PwMS. Twenty PwMS and 20 Controls completed a reach and hold task with simultaneous electroencephalography recorded to determine if increased Tv in PwMS was associated with greater levels of kinematic and neurologic impairment. Compared to Controls, PwMS moved slower and with greater variability, had increased sensory response delays, and decreased neural responses in occipital and parietal regions. Increased Tv was correlated with the Nine Hole Peg Test (NHPT) performance for PwMS who had more impairment (assessed via NHPT) and showed varying effects on the neurologic response to the task. Specifically, Tv was correlated with temporal delays in parietal channels for PwMS with less impairment while Tv of more impaired PwMS was inversely correlated with peak amplitude across parietal, somatosensory, and frontal channels. It could be that PwMS with less impairment are able to compensate for increased processing delays by moving slower, while those with greater impairment are more limited in how compensation may occur.