BACKGROUND Varying treatment outcomes in transcranial electrical stimulation (tES) recipients may depend on the amount of current reaching the brain. Brain atrophy associated with normal aging may affect tES current delivery to the brain. Computational models have been employed to compute predicted tES current inside the brain. This study is the largest study that uses computational models to investigate tES field distribution in healthy older adults. METHODS Individualized head models from 587 healthy older adults (mean = 73.9years, 51-95 years) were constructed to create field maps. Two electrode montages (F3-F4, M1-SO) with 2 mA input current were modeled using ROAST with modified codes. A customized template of healthy older adults, the UFAB-587, was created from the same dataset and used to warp individual brains into the same space. Warped models were analyzed to determine the relationship between computed field measures, brain atrophy and age. MAIN RESULTS Computed field measures were inversely correlated with brain atrophy (R2 = 0.0829, p = 1.14e-12). Field pattern showed negative correlation with age in brain sub-regions including part of DLPFC and precentral gyrus. Mediation analysis revealed that the negative correlation between age and current density is partially mediated by brain-to-CSF ratio. CONCLUSIONS Computed field measures showed decreasing amount of tES current reaching the brain with increasing atrophy. Therefore, adjusting current dose by modifying tES stimulation parameters in older adults based on degree of atrophy may be necessary to achieve desired stimulation benefits. Results from this study may inform future tES application in healthy older adults.

中文翻译：

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模拟老化大脑中的经颅电刺激

背景 经颅电刺激 (tES) 接受者的不同治疗结果可能取决于到达大脑的电流量。与正常衰老相关的脑萎缩可能会影响 tES 电流输送到大脑。计算模型已被用于计算大脑内的预测 tES 电流。这项研究是最大的研究，它使用计算模型来调查健康老年人的 tES 场分布。方法 构建了来自 587 名健康老年人（平均年龄 = 73.9 岁，51-95 岁）的个性化头部模型以创建现场图。输入电流为 2 mA 的两个电极蒙太奇 (F3-F4, M1-SO) 使用 ROAST 和修改后的代码进行建模。健康老年人的定制模板 UFAB-587 是从相同的数据集创建的，用于将个体大脑扭曲到相同的空间。分析扭曲模型以确定计算场测量值、脑萎缩和年龄之间的关系。主要结果 计算场测量值与脑萎缩呈负相关（R2 = 0.0829，p = 1.14e-12）。在包括部分 DLPFC 和中央前回在内的大脑亚区中，场模式与年龄呈负相关。中介分析显示，年龄和电流密度之间的负相关部分是由脑与脑脊液的比率介导的。结论 计算场测量显示随着萎缩的增加，到达大脑的 tES 电流量减少。因此，可能需要根据萎缩程度通过修改老年人的 tES 刺激参数来调整当前剂量，以实现所需的刺激益处。这项研究的结果可能会为未来 tES 在健康老年人中的应用提供信息。