Spinal excitation to enhance mobility in elderly adults

众所周知，与年龄相关的大脑和外周神经损伤会导致 步行功能。与年龄相关的脊髓损伤也是一个可能的因素，正如文献所述 描述了脊髓结构和功能随年龄增长的各种变化。具体地说，老年人脊柱 脊髓更不容易兴奋，传导信号更慢，而且容易受到神经噪音的影响。因此，我们正在发起 一项旨在通过干预年龄来增强老年退伍军人行走功能的新研究- 脊髓相关神经损害。拟议研究的目标是确定以下项目的可行性： 经皮脊髓直流电刺激的初步疗效和反应差异 (TsDC)和质感鞋垫，刺激脊髓运动回路，增强练习相关性 在障碍行走任务中的表现和保持能力。增强的实践和保留效果将支持 今后将努力将这一方法转化为更长期的康复干预。 兴奋性tsdcs是一种无创的神经调节方法，在这种方法中，相对较弱的电流 通过放置在皮肤上的电极传递到脊髓的所需区域。电流会影响到 不会引起动作电位的放电，而是被设计成使神经元更接近它们的放电 通过诱导膜电位的亚阈值去极化来实现阈值。当与 行为任务，tsDCS有可能以任务特定的方式上调神经回路并促进 Hebbian神经可塑性(‘火在一起，电线在一起’)。我们将使用先前建立的电极剪辑 在练习复杂的障碍穿越任务时，将兴奋性tsDCs传递到腰椎脊髓。 我们还建议将纹理鞋垫的使用与tsDCS结合起来。这种组合方法可能是 一种同时优化脊髓对下行和下行输入的反应性的有效策略 将兴奋信号上升至运动控制的脊椎中枢。一个预期的好处是增加 脊髓运动回路的兴奋是行走执行需求的减少，通过测量 前额叶皮质激活。我们的研究表明，老年人严重依赖薪酬管理。 边走边控制。这被广泛认为是包括跌倒在内的不良后果的风险因素。 我们提出了一项平行分组研究设计，其中40名有行走障碍的老年人和 演示补偿性执行运动控制策略将随机分为四组： 1)具有光滑鞋垫的主动tsDC(主动/平滑)；2)具有平滑鞋垫的假tsDC(假/光滑)；3) 具有纹理鞋垫的主动TSDC(活动/纹理)；以及4)具有纹理鞋垫的假TSDC(假/纹理)。 参与者将被蒙在鼓里，无法进行小组分配。在接受刺激的同时，参与者将参与20 在标准化的障碍赛道上进行几分钟的步行练习。紧接在此之前和之后 在练习中，每个参与者都将在以最快的安全速度在球场上行走时接受评估。练习- 相关的成绩提升将通过步行速度和其他生物力学指标来量化。保留 绩效收益也将在两天后的另一次访问中进行评估。TSDC诱导的脊髓改变 兴奋性将通过测量比目鱼肌H反射来评估。步行的执行需求将被评估为 前额叶皮质激活，用功能性近红外光谱(FNIRS)测量。对年龄的干预- 相关的脊髓损伤以改善行走功能是一个有希望但尚未开发的研究领域。 建议的干预技术成本低，可翻译为真实世界的设置，这增强了 这项工作对老年退伍军人的福祉具有潜在的长期影响。

It is well known that age-related impairments of the brain and peripheral nerves contribute to a decline in walking function. Age-related impairment of the spinal cord is also a likely contributing factor, as the literature describes a variety of changes in spinal cord structure and function with aging. Specifically, the elderly spinal cord is less excitable, conducts signals more slowly, and is subject to neural noise. Therefore, we are initiating a new line of research with the goal of enhancing walking function in elderly Veterans by intervening on age- related neural impairment of the spinal cord. The objective of the proposed study is to establish the feasibility, preliminary efficacy, and variance of response for using transcutaneous spinal direct current stimulation (tsDCS) and textured shoe insoles to excite spinal locomotor circuits and enhance practice-related performance and retention on an obstacle walking task. Enhanced practice and retention effects will support future efforts to translate this approach into a longer term rehabilitation intervention. Excitatory tsDCS is a non-invasive neuromodulation approach in which a relatively weak electrical current is delivered to the desired region of the spinal cord via electrodes placed on the skin. The electrical current does not cause discharge of action potentials, but rather is designed to bring neurons closer to their discharge threshold by inducing a sub-threshold depolarization of membrane potentials. When combined with a behavioral task, tsDCS has the potential to upregulate neural circuits in a task-specific manner and promote Hebbian neuroplasticity (‘fire together, wire together’). We will use a previously established electrode montage to deliver excitatory tsDCS to the lumbosacral spinal cord during practice of a complex obstacle walking task. We also propose to combine the use of textured shoe insoles with tsDCS. This combinatorial approach may be a potent strategy for simultaneously optimizing spinal responsiveness to input from both descending and ascending excitatory signals to spinal centers of locomotor control. One anticipated benefit of increasing the excitation of spinal locomotor circuits is a reduction in the executive demand of walking, as measured by prefrontal cortical activation. Our research shows that elderly adults rely heavily on compensatory executive control while walking. This is widely considered to be a risk factor for adverse outcomes including falls. We propose a parallel groups study design in which 40 older adults who have walking deficits and who demonstrate a compensatory executive locomotor control strategy will be randomized into one of four groups: 1) active tsDCS with smooth insoles (active/smooth); 2) sham tsDCS with smooth insoles (sham/smooth); 3) active tsDCS with textured insoles (active/textured); and 4) sham tsDCS with textured insole (sham/textured). Participants will be blinded to group assignment. While receiving stimulation, participants will engage in 20 minutes of walking practice over a standardized obstacle course. Immediately prior to and following the practice, each participant will be assessed while walking over the course at their fastest safe pace. Practice- related gains in performance will be quantified by walking speed and other biomechanical metrics. Retention of performance gains will also be assessed at a separate visit 2 days later. tsDCS-induced changes in spinal excitability will be assessed by measuring soleus H-reflex. Executive demand of walking will be assessed as prefrontal cortical activation, measured with functional near infrared spectroscopy (fNIRS). Intervening on age- related impairment of the spinal cord to improve walking function is a promising but untapped area of research. The proposed intervention techniques are low cost and translatable to real-world settings, which enhances the potential long term impact of this work on the well-being of aging Veterans.