Effects of Dual Tasking on the Neural Control System Underlying Mobility in Adults with Multiple Sclerosis

Background: There is increasing evidence to suggest that dual tasking, reflective of cognitive motor interference, is particularly difficult for individuals with multiple sclerosis (MS) and may put those with attentional deficits at greater risk of falling. While it is well recognized that gait characteristics are affected when concurrently completing cognitive tasks, how various cognitive loads differentially impact the neural control system underlying mobility in MS warrants further examination. 

Objectives: The purpose of this study was to examine dual tasking while walking in adults with MS and their healthy counterparts.

Methods: Twelve individuals with MS and eight matched controls participated in the study. Each participant walked at a self-selected pace back and forth along a 25-foot path: 1) as a single task, 2) while concurrently completing an auditory Stroop task, and 3) while concurrently completing a backward serial counting task. Data from wireless inertial sensors were used to compute average forward and lateral peak anticipatory postural adjustments (APAs) for step initiation, cadence, stride length, gait speed, double support time, and turning duration and velocity for each participant during each task. Factorial repeated measures ANOVAs and post-hoc analyses were conducted to compare the main effects within group across conditions and the interaction effect between group and condition on each dependent variable. 

Results: Serial backward counting resulted in significantly slower cadence compared to both the single task of walking and walking with Stroop. Dual tasking significantly increased double support time and decreased gait speed compared to walking alone, although there was no significant difference between the two dual task conditions. Significant differences were observed in cadence, double support, and gait speed between groups, but not in stride length. Effect size for all significant main effects as well as between group effects were large. There was no main effect of task condition on APAs for step initiation or turning.

Conclusions: These results suggest that different cognitive tasks have varied effects on the neural control system underlying walking in those with MS. Confirming that the control of gait in people with MS is differentially impacted by cognitive-motor interference has important implications for targeted fall prevention programs.