Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong SAR, China.
Guangdong Engineering Technology Research Center for Translational Medicine of Mental Disorders, Guangzhou, China.
J Alzheimers Dis. 2019;67(4):1331-1341. doi: 10.3233/JAD-180732.
Scalp to cortex distance (SCD), as a key technological parameter, has been highlighted in the guidelines of non-invasive brain stimulation. However, in the context of age-related brain changes, the region-specific SCD and its impact on stimulation-induced electric field remain unclear.
This study aimed to investigate the region-specific SCD and its relationship with morphometric features and cognitive function in age- and disease-specific populations.
We analyzed the SCD and cortical thickness (CT) of left primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) in 214 cognitively normal adults and 43 dementia patients. CT-adjusted SCD was used to control the influence of CT on SCD. Head model was developed to simulate the impact of SCD on the electric field induced by transcranial electrical stimulation.
We found age-related increased SCD in the left DLPFC (p < 0.001), but not M1 (p = 0.134), and dementia-related increased SCD in both left DLPFC (p < 0.001) and M1 (p < 0.001). CT-adjusted SCD showed greater region-specific impact on left DLPFC rather than M1. The electric field induced by stimulation was consequently decreased with the increased SCD across normal aging and dementia groups.
Age and dementia have differential impacts on the SCDs of left DLPFC and M1. The findings suggest that it is important to be aware of region-specific distance measures when conducting neuromodulation in individuals with old age and dementia.
头皮到皮层距离（SCD）作为一项关键技术参数，已在非侵入性脑刺激指南中得到强调。然而，在与年龄相关的脑变化背景下，特定区域的 SCD 及其对刺激诱导电场的影响尚不清楚。
本研究旨在探讨特定区域的 SCD 及其与年龄和疾病特定人群的形态特征和认知功能的关系。
我们分析了 214 名认知正常成年人和 43 名痴呆症患者左侧初级运动皮层（M1）和背外侧前额叶皮层（DLPFC）的 SCD 和皮质厚度（CT）。使用 CT 校正后的 SCD 来控制 CT 对 SCD 的影响。建立头部模型以模拟 SCD 对经颅电刺激诱导的电场的影响。
我们发现左侧 DLPFC 的 SCD 与年龄相关增加（p<0.001），而 M1 则无相关性（p=0.134），并且左侧 DLPFC 和 M1 的 SCD 与痴呆症相关增加（p<0.001）。CT 校正后的 SCD 对左侧 DLPFC 的区域特异性影响更大，而对 M1 的影响较小。随着正常老化和痴呆症组中 SCD 的增加，刺激诱导的电场相应减少。
年龄和痴呆症对左侧 DLPFC 和 M1 的 SCD 有不同的影响。研究结果表明，在进行老年人和痴呆症患者的神经调节时，注意特定区域的距离测量非常重要。
