Neuromechanisms of falls in older adults with MCI: Targeting assessment and training of reactive balance control

轻度认知障碍(MCI)发生在从正常认知到痴呆症的连续过程中，影响到几乎 四分之一的人年龄在70-79岁之间，在此之后，患病率每十年急剧增加。虽然 大多数患有MCI(OAwMCI)的老年人在日常生活中都是独立的，他们有显著的 与认知完好的同类相比，摔倒的可能性更大。除了认知缺陷， 患有MCI的人可能会经历运动功能障碍，包括步态和平衡方面的缺陷。当发生变化时 姿势控制和步态功能已经在这一人群中进行了彻底的调查，反应 平衡控制和保护性步进反应，用于从不可预测的、较大的 外部扰动还没有被广泛研究过。此外，尽管OAwMCI显示出较慢的速度 适应和运动学习与健康的同龄人相比，还不清楚 OAwMCI可以通过反复暴露在意想不到的干扰中来适应特定任务的训练，这是健康的 老年人(OA)这样做。此外，众所周知，OAwMCI的双重任务绩效较差 无论是站姿还是步态。这种表现与执行功能、视觉运动功能受损有关。 和空间意识。然而，在受干扰的站姿和步态中的双重任务表现与 OAwMCI尚未对跌倒风险增加进行调查。此外，众所周知，更高的 皮质中枢在调节反应性平衡控制中起着至关重要的作用。有趣的是，在OAwMCI， 在感觉和认知挑战下的意志力平衡控制与增加的休息状态相关 激活默认模式网络，降低白质完整性和灰质体积。 然而，检验结构完整性受损与 神经与反应性平衡控制措施相关，并导致更高的跌倒发生率 人口。我们之前的研究表明，有两个关键变量，即稳定性和垂直性的无功控制 肢体支持，导致了超过90%的实验室滑倒在骨关节炎。因此，改善这些关键变量 有助于显著降低骨性关节炎的跌倒风险。然而，这种以任务为基础的干预研究 在MCI人群中是缺乏的。为了填补文献中的空白，我们的研究建议调查 外源性平衡扰动下反应性步进反应的神经力学差异 OAwMCI与OAwMCI相比。此外，我们的研究建议将反应稳定性控制与 大脑结构和功能的连通性。最后，我们的研究建议确定一项新任务的效果- 基于特定扰动的认知运动干预对提高OAwMCI患者抗跌倒能力的作用。

Mild cognitive impairment (MCI) occurs along a continuum from normal cognition to dementia and affects nearly a quarter of individuals 70-79 years old, with the prevalence drastically increasing each decade after. Although most older adults with MCI (OAwMCI) are independent in their daily living, they are known to have significantly greater likelihood of falls compared to their cognitively intact counterparts. In addition to cognitive deficits, persons with MCI can experience motor dysfunction, including deficits in gait and balance. While changes in stance posture control and gait functionality have been thoroughly investigated in this population, reactive balance control and protective stepping responses that are recruited to recover from unpredictable, larger external perturbations have not yet been extensively examined. Additionally, though OAwMCI show slower adaptation and motor learning in comparison to their healthy counterparts, it remains to be unknown whether OAwMCI can adapt to task-specific training via repeated exposure to unpredicted perturbations as healthy older adults (OA) do. Furthermore, it is well established that OAwMCI have worse dual-task performance during both stance and gait. This presentation is related to impaired executive function, visuomotor function and spatial awareness. However, dual-task performance during perturbed stance and gait in association with increased fall-risk has not yet been investigated in OAwMCI. In addition, it is well-established that higher cortical centers play a vital role in modulation of reactive balance control. Interestingly, in OAwMCI, the decline in volitional balance control under sensory and cognitive challenges is corelated to an increased resting state activation of the default mode network, reduced white matter integrity and reduced gray matter volume. However, there is limited evidence examining the association between impaired structural integrity and neural correlates with reactive balance control measures and resulting higher occurrence of falls in this population. Our previous research has shown that two key variables, reactive control of stability and vertical limb support, contribute to more than 90% of laboratory slip-falls in OA. Thus, improving these key variables can contribute to significant reduction in fall risk in OA. However, such task-specific intervention-based studies are lacking in the MCI population. To fill the gap in the literature, our study proposes to investigate the differences in neuromechanics of reactive stepping responses to externally-induced balance perturbations in OAwMCI compared to OA. Further, our study proposes to relate reactive stability control to changes in brain structural and functional connectivity. Lastly, our study proposes to determine the effect of a novel task- specific perturbation-based cognitive-motor intervention for enhancing fall-resisting skills in OAwMCI.