Department of Sport and Health Sciences, Technische Universität München, Munich, Germany; School of Psychology, University of Birmingham, Birmingham, United Kingdom.
Neuropsychologia. 2013 Sep;51(11):2142-53. doi: 10.1016/j.neuropsychologia.2013.07.009. Epub 2013 Jul 19.
Limited information processing capacity in the brain necessitates task prioritisation and subsequent adaptive behavioural strategies for the dual-task coordination of locomotion with severe concurrent cognitive loading. Commonly observed strategies include prioritisation of gait at the cost of reduced performance in the cognitive task. Alternatively alterations of gait parameters such as gait velocity have been reported presumably to free processing capacity for the benefit of performance in the cognitive task. The aim of this study was to describe the neuroanatomical correlates of adaptive behavioural strategies in cognitive-motor dual-tasking when the competition for information processing capacity is severe and may exceed individuals' capacity limitations.
During an fMRI experiment, 12 young adults performed slow continuous, auditorily paced bilateral anti-phase ankle dorsi-plantarflexion movements as an element of normal gait at .5 Hz in single and dual task modes. The secondary task involved a visual, alphabetic N-back task with presentation rate jittered around .7 Hz. The N-back task, which randomly occurred in 0-back or 2-back form, was modified into a silent counting task to avoid confounding motor responses at the cost of slightly increasing the task's general coordinative complexity. Participants' ankle movements were recorded using an optoelectronic motion capture system to derive kinematic parameters representing the stability of the movement timing and synchronization. Participants were instructed to perform both tasks as accurately as possible.
Increased processing complexity in the dual-task 2-back condition led to significant changes in movement parameters such as the average inter-response interval, the coefficient of variation of absolute asynchrony and the standard deviation of peak angular velocity. A regions-of-interest analysis indicated correlations between these parameters and local activations within the left inferior frontal gyrus (IFG) such that lower IFG activations coincided with performance decrements.
Dual-task interference effects show that the production of periodically timed ankle movements, taken as modelling elements of the normal gait cycle, draws on higher-level cognitive resources involved in working memory. The interference effect predominantly concerns the timing accuracy of the ankle movements. Reduced activations within regions of the left IFG, and in some respect also within the superior parietal lobule, were identified as one factor affecting the timing of periodic ankle movements resulting in involuntary 'hastening' during severe dual-task working memory load. This 'hastening' phenomenon may be an expression of re-automated locomotor control when higher-order cognitive processing capacity can no longer be allocated to the movements due to the demands of the cognitive task. The results of our study also propose the left IFG as a target region to improve performance during dual-task walking by techniques for non-invasive brain stimulation.
大脑的信息处理能力有限，因此需要对任务进行优先级排序，并采取相应的适应行为策略，以协调运动和严重的并发认知负荷。常见的策略包括优先考虑步态，而牺牲认知任务的表现。或者，已经报道了步态参数的改变，例如步态速度，大概是为了为认知任务的表现释放处理能力。本研究的目的是描述在信息处理能力竞争激烈且可能超过个体能力限制时，认知运动双重任务中适应行为策略的神经解剖学相关性。
在 fMRI 实验中，12 名年轻人在单任务和双任务模式下以.5 Hz 的频率进行缓慢连续的、听觉节拍的双侧反向踝关节背屈-跖屈运动，作为正常步态的一部分。次要任务涉及视觉、字母 N 回任务，呈现率围绕.7 Hz 波动。N 回任务以 0 回或 2 回的形式随机出现，修改为无声计数任务，以避免因运动反应而混淆，代价是略微增加任务的一般协调性复杂性。参与者的踝关节运动使用光电运动捕捉系统记录，以得出代表运动定时和同步稳定性的运动学参数。参与者被指示尽可能准确地执行两项任务。
在双重任务 2 回条件下，处理复杂性增加导致运动参数发生显著变化，例如平均反应间间隔、绝对异步的变异系数和峰值角速度的标准差。感兴趣区域分析表明，这些参数与左额下回（IFG）内的局部激活之间存在相关性，使得较低的 IFG 激活与表现下降相吻合。
双重任务干扰效应表明，周期性定时踝关节运动的产生，作为正常步态周期的建模元素，利用了与工作记忆相关的更高层次的认知资源。干扰效应主要涉及踝关节运动的定时准确性。左额下回内的激活减少，在某些方面也涉及顶叶上回内的激活，被确定为影响周期性踝关节运动定时的一个因素，导致在严重的双重任务工作记忆负荷下的不自主“加速”。这种“加速”现象可能是由于认知任务的需求导致无法再将更高阶的认知处理能力分配给运动时，重新自动化运动控制的表现。我们的研究结果还提出左额下回作为目标区域，通过非侵入性脑刺激技术来提高双重任务行走时的表现。
