Comparison of practice-related changes in dual task walking performance and neural efficiency between older adults with progressive and relapsing-remitting multiple sclerosis

Background: There is limited research comparing both performance and brain control of walking between older adults with progressive and relapsing-remitting MS. Objective: This study compared older adults with progressive and relapsing-remitting MS for differences in prefrontal cortex (PFC) activation in single- and dual-task-walking and practice-related effects on neural efficiency, walking, and cognitive performances. Methods: Older adults with progressive (n = 32, age=65±6ys) and relapsing-remitting (n = 63, age=65±4ys) MS completed three conditions (single-task walk, single-task-alpha, i.e., cognitive interference task, and dual-task-walk) with three repeated trials wherein we measured PFC oxygenated hemoglobin (HbO₂), stride velocity and letter generation rate. Task, trial, and group effects and interactions were analyzed using linear mixed effects models. Results: The task-related (i.e. single-to-dual task walking) increase in PFC HbO₂ was greater in progressive than in relapsing-remitting MS (p < 0.001), while the practice-related decrease in dual-task PFC HbO₂ was smaller in progressive than in relapsing-remitting MS (p < 0.001). Progressive MS was associated with slower stride velocity overall, but repeated trials resulted in faster stride velocity and correct letter generation rate for both groups. Conclusions: Practice-related improvements in cognitive and motor performances coupled with reduced PFC HbO₂ over dual-task walking trials suggest attenuated improvements of efficiency in brain control of attention-demanding locomotion in progressive MS.