Psychology, School of Social Sciences, Nanyang Technological University, Singapore.
Centre for Research and Development in Learning (CRADLE), Nanyang Technological University, Singapore.
Brain Stimul. 2022 Jan-Feb;15(1):125-140. doi: 10.1016/j.brs.2021.11.018. Epub 2021 Nov 23.
The observed variability in the effects of transcranial direct current stimulation (tDCS) is influenced by the amount of current reaching the targeted region-of-interest (ROI). Age and sex might affect current density at target ROI due to their impact on cortical anatomy. The present tDCS simulation study investigates the effects of cortical anatomical parameters (volumes, dimension, and torque) on simulated tDCS current density in healthy young, middle-aged, and older males and females.
Individualized head models from 240 subjects (120 males, 18-87 years of age) were used to identify the estimated current density (2 mA current intensity, 25 cm electrode) from two simulated tDCS montages (CP5_CZ and F3_FP2) targeting the inferior parietal lobule (IPL) and middle frontal gyrus (MFG), respectively. Cortical parameters including segmented brain volumes (cerebrospinal fluid [CSF], grey and white matter), cerebral-dimensions (length/width &length/height) and brain-torque (front and back shift, petalia, and bending) were measured using the magnetic resonance images (MRIs) from each subject. The present study estimated sex differences in current density at these target ROIs mediated by these cortical parameters within each age group.
For both tDCS montages, females in the older age group received higher current density than their male counterparts at the target ROIs. No sex differences were observed in the middle-aged group. Males in the younger age group had a higher current density than females, only for the parietal montage. Across all age groups, CSF, and grey matter volumes significantly predicted the current intensity estimated at the target sites. In the older age group only, brain-torque was a significant mediator of the sex difference.
Our findings demonstrate the presence of sex differences in the simulated tDCS current density, however this pattern differed across age groups and stimulation locations. Future studies should consider influence of age and sex on individual cortical anatomy and tailor tDCS stimulation parameters accordingly.
经颅直流电刺激（tDCS）的效果存在可变性，这受到到达目标感兴趣区域（ROI）的电流量的影响。年龄和性别可能会通过对皮质解剖结构的影响而影响目标 ROI 的电流密度。本 tDCS 模拟研究调查了皮质解剖参数（体积、尺寸和扭矩）对健康年轻、中年和老年男性和女性模拟 tDCS 电流密度的影响。
使用来自 240 名受试者（120 名男性，18-87 岁）的个体化头部模型，从两种模拟 tDCS 导联（CP5_CZ 和 F3_FP2）中识别出估计的电流密度（2 mA 电流强度，25 cm 电极），分别针对下顶叶（IPL）和中额回（MFG）。使用每个受试者的磁共振成像（MRI）测量皮质参数，包括分割的脑体积（脑脊液 [CSF]、灰质和白质）、大脑尺寸（长度/宽度和长度/高度）和脑扭矩（前后移位、花瓣和弯曲）。本研究估计了每个年龄组内这些皮质参数介导的这些 ROI 中的电流密度的性别差异。
对于两种 tDCS 导联，年龄较大的女性在目标 ROI 处的电流密度高于男性。在中年组中没有观察到性别差异。在年轻组中，男性的电流密度高于女性，仅在顶叶导联中如此。在所有年龄组中，CSF 和灰质体积显著预测了目标部位的电流强度。仅在老年组中，脑扭矩是性别差异的重要介导因素。
我们的研究结果表明，模拟 tDCS 电流密度存在性别差异，但这种模式因年龄组和刺激部位而异。未来的研究应考虑年龄和性别对个体皮质解剖结构的影响，并相应地调整 tDCS 刺激参数。
