Abstract
Persons with multiple sclerosis (pwMS) experience declines in physical and cognitive abilities and are challenged by dual-tasks. Dual-tasking causes a drop in performance, or what is known as dual-task cost (DTC). This study examined DTC of walking speed (WS) and cognitive performance (CP) in pwMS and healthy controls (HCs) and the effect of dual-tasking on cortical activation of bilateral premotor cortices (PMC) and bilateral supplementary motor area (SMA). Fourteen pwMS and 14 HCs performed three experimental tasks: (1) single cognitive task while standing (SingCog); (2) single walking task (SingWalk); and (3) dual-task (DualT) that included concurrent performance of the SingCog and SingWalk. Six trials were collected for each condition and included measures of cortical activation, WS and CP. WS of pwMS was significantly lower than HC, but neuropsychological (NP) measures were not significantly different. pwMS and HC groups had similar DTC of WS, while DTC of CP was only significant in the MS group; processing speed and visual memory predicted 55% of this DTC. DualT vs. SingWalk recruited more right-PMC activation only in HCs and was associated with better processing speed. DualT vs. SingCog recruited more right-PMC activation and bilateral-SMA activation in both HC and pwMS. Lower baseline WS and worse processing speed measures in pwMS predicted higher recruitment of right-SMA (rSMA) activation suggesting maladaptive recruitment. Lack of significant difference in NP measures between groups does not rule out the influence of cognitive factors on dual-tasking performance and cortical activations in pwMS, which might have a negative impact on quality of life.
Highlights
One of the hallmarks, burdensome features of multiple sclerosis (MS) involves the interrelated deterioration of both physical and cognitive performance (CP), perhaps based on co-occurring damage in neural regions that are important for those functions (Benedict et al, 2011; Motl et al, 2016; Cattaneo et al, 2017)
DTC on cognitive task performance (DTCC), i.e., number of serial 7’s answers, dropped by 19.3% (±30%) in the MS group and increased by 11% (±39%) in the healthy controls (HCs) group, where the HC group participants performed better under dual-task condition compared to single cognitive task (SingCog) (F = 5.8, p = 0.023, ηp2 = 0.21)
Higher dual-task cost (DTC) of serial 7’s performance in the MS group was predicted by worse Brief Visuospatial Memory Test-Revised (BVMT-R) (F = 5.7, p = 0.034, ηp2 = 0.3) and Symbol Digit Modalities Test (SDMT) scores (F = 5.3, p = 0.036, ηp2 = 0.29)
Summary
Burdensome features of multiple sclerosis (MS) involves the interrelated deterioration of both physical and cognitive performance (CP), perhaps based on co-occurring damage in neural regions that are important for those functions (Benedict et al, 2011; Motl et al, 2016; Cattaneo et al, 2017). The increased attentional demands associated with dual-tasking during walking can lead to increased rate of error and put persons with MS (pwMS) at an elevated risk of falling or getting injured (Wajda et al, 2013). One recent meta-analytic study reported that complex dual-tasking has negative effects on postural stability in pwMS, posing an elevated fall risk (Ghai et al, 2017). By extension, such an elevated fall risk further reduces the quality of life, ability to perform activities of daily living, and sustaining stable employment (Raggi et al, 2016). As such, quantifying the impact of dual-tasking during walking in pwMS is paramount
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