Abstract
The need to perform multiple tasks more or less simultaneously is a common occurrence during walking in daily life. Performing tasks simultaneously typically impacts task performance negatively. Hypothetically, such dual-task costs may be explained by a lowered state of preparation due to competition for attentional resources, or alternatively, by a ‘bottleneck’ in response initiation. Here, we investigated both hypotheses by comparing ‘StartReact’ effects during a manual squeezing task under single-task (when seated) and dual-task (when walking) conditions. StartReact is the acceleration of reaction times by a startling stimulation (a startling acoustic stimulus was applied in 25% of trials), attributed to the startling stimulus directly releasing a pre-prepared movement. If dual-task costs are due to a lowered state of preparation, we expected trials both with and without an accompanying startling stimulus to be delayed compared to the single-task condition, whereas we expected only trials without a startling stimulus to be delayed if a bottleneck in response initiation would underlie dual-task costs. Reaction times of the manual squeezing task in the flexor digitorum superficialis and extensor carpi radialis muscle were significantly delayed (approx. 20 ms) when walking compared to the seated position. A startling acoustic stimulus significantly decreased reaction times of the squeezing task (approx. 60 ms) both when walking and sitting. Dual-task costs during walking are, therefore, likely the result of lowered task preparation because of competition for attentional resources.
Highlights
Dual tasking is the simultaneous performance of two attention-demanding tasks with different goals, whereby one task can be denoted as the primary and the other as the secondary task (Beauchet and Berrut 2006)
We investigated the mechanism underlying dual-task costs during gait, by comparing StartReact effects on a manual squeezing task performed under single-task conditions and dual-task conditions
Our findings suggest that dual-task costs during walking are the result of a lowered state of task preparation because of competition for attentional resources
Summary
Dual tasking is the simultaneous performance of two attention-demanding tasks with different goals, whereby one task can be denoted as the primary and the other as the secondary task (Beauchet and Berrut 2006). Donders Institute for Brain, Cognition and Behaviour, Centre of Expertise for Parkinson and Movement Disorders, Nijmegen, The Netherlands 5 SRH University of Applied Health Sciences, Gera, Campus Stuttgart, Stuttgart, Germany under daily life situations, we often perform such secondary tasks, for example when talking to someone or when handling a mobile phone. Under these circumstances, gait can be seen as the primary task, and talking or handling a mobile phone as the secondary task. Evidence for the bottleneck hypothesis came from studies that reported additional dual-task constraints when the primary and secondary task had the same effector (e.g., when both were manual in nature) compared to tasks where the primary and secondary task had different effectors (e.g., vocal and manual in nature)
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