Facilitation of supplementary motor area excitability improves dual-task walking in young adults

Abstract

Activations of the DLPFC and SMA have been shown to correlate with dual-task walking. However, very few investigations have directly perturbed the activations of these areas to establish a cause-and-effect relationship. The objectives of this study were: 1) to investigate the role of DLPFC and SMA in dual-task walking using rTMS and 2) to determine whether the secondary task difficulty mediates the roles of these cortical areas. Nineteen young healthy adults were divided into two groups: Count-by-3 s (N = 9) and Count-by-7 s (N = 10) groups. During dualtask walking, the Count-by-3 s group walked and counted backward by 3 s while the other group counted backward by 7. Each participant received facilitatory rTMS (5 Hz) administered to the left DLPFC, SMA and M1 across 3 sessions (approximately a week apart). Single- and dual-task walking were assessed both before and after rTMS. Gait speed under the 2 walking conditions was analyzed with repeated measure ANOVA. rTMS to the SMA significantly increased dual-task walking speed (p = .02) but not singletask walking speed. In contrast, rTMS to the DLPFC or M1 did not result in any significant changes in gait speed. Secondary task difficulty did not moderate the effects of rTMS on dual-task gait because both groups had similar changes in gait performance after rTMS. SMA is an important neural substrate mediating dual-task walking and might be a therapeutic target for gait intervention.