Optimizing transcranial direct current stimulation (tDCS) to improve dual task gait and balance in older adults

项目概述：站立和行走几乎总是与其他认知任务同步完成 比如说话、阅读或做决定。执行这种重要类型的“双重任务”的能力是 对日常活动至关重要，并依赖于一个人有效激活适当大脑网络的能力 包括左背外侧前额叶皮层（dlPFC）。经颅直流电刺激（tDCS）是一种 安全、非侵入性的技术可以选择性地调节大脑兴奋性（即，激活的可能性）， 在置于头皮上的电极之间传递低电平电流。我们通过一系列的实验证明了 的研究表明，单次20分钟的tDCS暴露靶向左dlPFC-通过两个大的 海绵电极-减少双重任务成本，以衡量站立姿势控制和步态，当测试 紧接着刺激。尽管如此，我们和其他人也观察到相对较高的受试者间 这种“传统的”双极形式的tDCS的效果的可变性。我们认为，这种有效性的变化 当使用大的海绵电极时， 结合头部和大脑解剖结构的个体差异，显著改变了电流流动， 在目标大脑区域产生电场。在这个项目中，我们将应用tDCS的最新进展 建模和管理：1）使用以下方法对老年人中传统tDCS产生的电场进行建模 他们的个人结构脑MRI，和2）开发个性化的tDCS-通过八个小的阵列提供 凝胶电极-通过使用优化算法来确定电极位置和电流参数 所需的电场与感兴趣的大脑区域。我们的具体目标是检查 个性化tDCS、传统tDCS和假刺激对双任务站立的即刻后效应 在老年人中行走。我们的研究人群将是没有明显疾病或疾病的老年男性和女性， 然而对于定义为双重任务成本的较差基线双重任务性能（即，减少）的步态速度， 至少20%的诱导同时执行串行减法任务时行走。我们假设 在参与者中，传统tDCS对站立和行走双重任务表现的影响将与 其中在左dlPFC目标上产生电场的特定分量。我们还假设， 个性化tDCS将诱导A）与个性化tDCS相比，个性化tDCS对双任务站立和行走性能的影响更大 与传统tDCS和假刺激相比，以及B）这些效应在个体之间更加一致， 与传统的TDCS相比。这个项目将提供重要的见解tDCS“剂量”，使我们能够 和许多其他研究人员，以更好地了解，控制和优化这种形式的非侵入性大脑 刺激个体头部和大脑解剖结构。预计还将证明个性化的tDCS，如 与传统方法相比，显著提高了观测效益的规模和一致性， 在脆弱的老年人中进行站立和行走的双重任务。

Project Summary: Standing and walking are almost always completed in unison with other cognitive tasks such as talking, reading or making decisions. The ability to perform this important type of “dual tasking” is critical to daily activities and dependent upon one’s capacity to effectively activate appropriate brain networks that include the left dorsolateral prefrontal cortex (dlPFC). Transcranial direct current stimulation (tDCS) is a safe, noninvasive technology that can selectively modulate brain excitability (i.e., the likelihood of activation) by passing low-level currents between electrodes placed upon the scalp. We have demonstrated through a series of studies that a single, 20-minute exposure of tDCS targeting the left dlPFC—administered via two large sponge electrodes—reduces dual task costs to metrics of standing postural control and gait, when tested immediately following stimulation. Still, we and others have also observed relatively high between-subject variability in the effects of this ‘traditional’ bipolar form of tDCS. We contend that this variability in effectiveness arises in part from relatively diffuse and unspecific current flow when using large sponge electrodes, in combination with individual variability in head and brain anatomy that significantly alters current flow and the generated electric field in the target brain region. In this project, we will apply recent advances in tDCS modeling and administration to 1) model the electric fields generated by traditional tDCS in older adults using their individual structural brain MRIs, and 2) develop personalized tDCS—delivered via an array of eight small gel electrodes—by using optimization algorithms to determine electrode placement and current parameters needed to generate desired electrical field with the brain region of interest. Our Specific Aim is to examine the immediate after-effects of personalized tDCS, traditional tDCS, and sham stimulation on dual task standing and walking in older adults. Our study population will be older men and women without overt disease or illness, yet with poor baseline dual task performance defined as a dual task cost (i.e., reduction) to gait speed of at least 20% induced by simultaneously performing a serial subtraction task when walking. We hypothesize that across participants, the effect of traditional tDCS on dual task standing and walking performance will correlate with a specific component of the electric field generated over the left dlPFC target. We also hypothesize that personalized tDCS will induce A) greater effects on dual task standing and walking performance as compared to traditional tDCS and sham stimulation, and B) these effects will be more consistent across individuals as compared to traditional tDCS. This project will provide important insights into tDCS “dosage” that will enable us and many other researchers to better understand, control, and optimize this form of noninvasive brain stimulation to individual head and brain anatomy. It is also expected to demonstrate that personalized tDCS, as compared to the traditional approach, significantly improves the size and consistency of observed benefits to dual task standing and walking in vulnerable older adults.