Department of Radiology, Gruss Magnetic Resonance Research Center, Albert Einstein College of Medicine, Bronx, NY, USA; Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY, USA.
Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, NY, USA.
Neuroimage. 2019 Apr 1;189:745-754. doi: 10.1016/j.neuroimage.2019.01.045. Epub 2019 Jan 30.
It has been well established over the last two decades that walking is not merely an automatic, motoric activity; it also utilizes executive function circuits, which play an increasingly important role in walking for older people and those with mobility and cognitive deficits. Dual-task walking, such as walking while performing a cognitive task, is a necessary skill for everyday functioning, and has been shown to activate prefrontal lobe areas in healthy older people. Another well-established point in healthy aging is the loss of grey matter, and in particular loss of frontal lobe grey matter volume. However, the relationship between increased frontal lobe activity during dual-task walking and loss of frontal grey matter in healthy aging remains unknown. In the current study, we combined oxygenated hemoglobin (HbO) data from functional near-infrared spectroscopy (fNIRS), taken during dual-task walking, with structural MRI volumetrics in a cohort of healthy older subjects to identify this relationship. We studied fifty-five relatively healthy, older participants (≥65 years) during two separate sessions: fNIRS to measure HbO changes between single-task (i.e., normal walking) and dual-task walking-while-talking, and high-resolution, structural MRI to measure frontal lobe grey matter volumes. Linear mixed effects modeling was utilized to determine the moderation effect of grey matter volume on the change in prefrontal oxygenated hemoglobin between the two walking tasks, while controlling for covariates including task performance. We found a highly significant interaction effect between frontal grey matter volume and task on HbO levels (p < 0.0001). Specifically, increased HbO levels during dual-task compared to single-task walking were associated with reduced frontal grey matter volume. Regional analysis identified bilateral superior and rostral middle gyri as the primary areas driving these results. The findings provide support for the concept of neural inefficiency: in the absence of behavioral gains, grey matter loss in relatively healthy, older individuals leads to over-activation of frontal lobe during a cognitively demanding walking task with established clinical and predictive utility.
在过去的二十年中，人们已经充分认识到，行走不仅仅是一种自动的运动活动；它还利用执行功能回路，这些回路在老年人和那些有运动和认知缺陷的人行走中发挥着越来越重要的作用。双重任务行走，例如在执行认知任务的同时行走，是日常功能的必要技能，并且已被证明可以在健康的老年人中激活前额叶区域。健康老龄化的另一个既定观点是灰质的丧失，特别是额叶灰质体积的丧失。然而，在健康老龄化中，双重任务行走期间前额叶活动增加与额部灰质丧失之间的关系尚不清楚。在当前的研究中，我们将来自功能近红外光谱（fNIRS）的含氧血红蛋白（HbO）数据与健康老年受试者的结构磁共振成像体计量学相结合，该研究对一个健康老年受试者队列进行了研究。我们在两个单独的会议期间研究了 55 名相对健康的老年人：fNIRS 用于测量单任务（即正常行走）和双重任务行走时说话之间的 HbO 变化，高分辨率结构 MRI 用于测量额叶灰质体积。线性混合效应模型用于确定灰质体积对两种行走任务之间前额叶含氧血红蛋白变化的调节作用，同时控制包括任务表现在内的协变量。我们发现灰质体积和任务对 HbO 水平的高度显著交互作用（p < 0.0001）。具体来说，与单任务行走相比，双重任务行走期间 HbO 水平的升高与额叶灰质体积减少有关。区域分析确定双侧额上和额中回是驱动这些结果的主要区域。这些发现为神经效率低下的概念提供了支持：在没有行为收益的情况下，相对健康的老年人的灰质丧失会导致在具有既定临床和预测效用的认知要求高的行走任务中过度激活额叶。
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