The relevance of dual-task walking to everyday ambulation is widely acknowledged, and numerous studies have demonstrated that dual-task interference can significantly impact recovery of functional walking in people with neurological disorders. The magnitude and direction of dual-task interference is influenced by the interaction between the two tasks, including how individuals spontaneously prioritize their attention. Therefore, to accurately interpret and characterize dual-task interference and identify changes over time, it is imperative to evaluate single and dual-task performance in both tasks, as well as the tasks relative to each other. Yet, reciprocal dual-task effects (DTE) are frequently ignored. The purpose of this perspective paper is to present a framework for measuring treatment effects on dual-task interference, specifically taking into account the interactions between the two tasks and how this can provide information on whether overall dual-task capacity has improved or a different attentional strategy has been adopted. In discussing the clinical implications of using this framework, we provide specific examples of using this method and provide some explicit recommendations for research and clinical practice.

This study investigated the interactions between gait and three different cognitive tasks in people after stroke. Thirteen people post-stroke who were living in the community, were able to walk 10 m without physical assistance, and could respond verbally to auditory stimuli participated. Participants performed a walking task alone, three different cognitive tasks while seated, and each cognitive task in combination with walking. Gait data were acquired continuously for approximately 3 min. Reaction time and accuracy were recorded for two of the cognitive tasks (visuospatial task, working memory task). Speech samples from the spontaneous speech task were analyzed on several dimensions of language. Significant dual task effects were observed for gait speed, stride time, average stride length, and cadence, but not for stride time variability. Speech produced more gait interference than memory and visuospatial tasks. Interference effects on cognition were minimal; only speech was significantly affected by concurrent walking. Narratives in the dual task condition had more pauses, shorter sentences, but more utterances with new information. Even though participants in this study were mobility-impaired, they prioritized the cognitive tasks. Future research should determine whether dual task training can reduce gait decrements in dual task situations in people after stroke.⋆ P Plummer-D'Amato was supported by NIDRR Fellowship (Award ID# EH133P020005). There was no other source of funding for this study.

Cognitive-motor interference (CMI) is evident when simultaneous performance of a cognitive task and a motor task results in deterioration in performance in one or both of the tasks, relative to performance of each task separately. The purpose of this review is to present a framework for categorizing patterns of CMI and to examine the specific patterns of CMI evident in published studies comparing single-task and dual-task performance of cognitive and motor tasks during gait and balance activities after stroke. We also examine the literature for associations between patterns of CMI and history of falls, as well as evidence for the effects of rehabilitation on CMI after stroke. Overall, this review suggests that during gait activities with an added cognitive task, people with stroke are likely to demonstrate significant decrements in motor performance only (cognitive-related motor interference) or decrements in both motor and cognitive performance (mutual interference). In contrast, patterns of CMI were variable among studies examining balance activities. Comparing people post-stroke with and without a history of falls, patterns and magnitude of CMI were similar for fallers and non-fallers. Longitudinal studies suggest that conventional rehabilitation has minimal effects on CMI during gait or balance activities. However, early phase pilot studies suggest that dual-task interventions may reduce CMI during gait performance in community-dwelling stroke survivors. It is our hope that this innovative and critical examination of the existing literature will highlight the limitations in current experimental designs and inform improvements in the design and reporting of dual-task studies in stroke.

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