Abstract
Background: Increasing evidence suggests that walking while performing a concurrent task negatively influences gait performance. However, it remains unclear how higher-level cognitive processes and coordination of limb movements are altered in challenging walking environments. This study investigated the influence of cognitive task complexity and walking road condition on the neutral correlates of executive function and postural control in dual-task walking.Methods: Twenty-four healthy young adults completed a series of overground walks with three walking road conditions (wide, narrow, with obstacles) with and without the concurrent n-back working memory tasks of two complexity levels (1-back and 3-back). Prefrontal brain activation was assessed by functional near-infrared spectroscopy. A three-dimensional motion analysis system was used simultaneously to measure gait performance and lower-extremity kinematics. Repeated measures analysis of variance were performed to examine the differences between the conditions.Results: In comparison with standing still, participants showed lower n-back task accuracy while walking, with the worst performance from the road with obstacles. Spatiotemporal gait parameters, lower-extremity joint movements, and the relative changes in oxygenated hemoglobin (HbO) concentration levels were all significantly different across the task complexity and walking path conditions. While dual-tasking participants were found to flex their hips and knees less, leading to a slower gait speed, longer stride time, shorter step length, and greater gait variability than during normal walking. For narrow-road walking, smaller ankle dorsiflexion and larger hip flexion were observed, along with a reduced gait speed. Obstacle negotiation was mainly characterized by increased gait variability than other conditions. HbO levels appeared to be lower during dual-task walking than normal walking. Compared to wide and obstacle conditions, walking on the narrow road was found to elicit a smaller decrement in HbO levels.Conclusion: The current study provided direct evidence that, in young adults, neural correlates of executive function and dynamic postural control tend to be altered in response to the cognitive load imposed by the walking environment and the concurrent task during ambulation. A shift of brain activation patterns between functionally connected networks may occur when facing challenging cognitive–motor interaction.
Highlights
In everyday life, it is common for individuals to be walking while concurrently engaging in another activities, such as passing through a circuitous obstacle course, watching street signs, recalling a shopping list, attending to verbal communication, or interacting with mobile devices
Our results suggested that compared to the single-task condition, the task workload perceived by healthy younger adults was higher under the DT conditions but was further increased as the cognitive task and road conditions became more challenging
While dual-tasking in the narrow road condition our participants were found to reduce their step length and increase stride time, resulting in a slower gait speed than in the other two road conditions (Figures 3A–C). These findings further extend the knowledge on obstacle negotiation behavior in healthy young adults by showing that compared to unobstructed walking, the additional motor coordination required while approaching obstacles could significantly destabilize gait patterns, regardless of whether they were performing a concurrent WM task or not (Figures 3D–F)
Summary
It is common for individuals to be walking while concurrently engaging in another activities, such as passing through a circuitous obstacle course, watching street signs, recalling a shopping list, attending to verbal communication, or interacting with mobile devices. Decreased gait speed in response to the additional demands of postural control under dual-tasking has been widely reported in prior studies involving mental arithmetic (Mirelman et al, 2014), VFT (Yogev-Seligmann et al, 2010), and texting on a mobile phone (Schabrun et al, 2014; Plummer et al, 2015). Increasing evidence suggests that walking while performing a concurrent task negatively influences gait performance. It remains unclear how higherlevel cognitive processes and coordination of limb movements are altered in challenging walking environments. This study investigated the influence of cognitive task complexity and walking road condition on the neutral correlates of executive function and postural control in dual-task walking
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