Department of Electrical Engineering and Automation, Aalto University, Espoo, Finland.
Department of Neurology, Fukushima Medical University, Fukushima, Japan; Fukushima Global Medical Science Center, Advanced Clinical Research Center, Fukushima Medical University, Fukushima, Japan.
Brain Stimul. 2018 Jan-Feb;11(1):166-174. doi: 10.1016/j.brs.2017.09.011. Epub 2017 Sep 27.
Despite recent developments in navigation and modeling techniques, the type and location of the structures that are activated by transcranial magnetic stimulation (TMS) remain unknown.
We studied the relationships between electrophysiological measurements and electric fields induced in the brain to locate the TMS activation site.
The active and resting motor thresholds of the first dorsal interosseous muscle were recorded in 19 subjects (7 female, 12 male, age 22 ± 4 years) using anteromedially oriented monophasic TMS at multiple locations over the left primary motor cortex (M1). Structural MR images were used to construct electric field models of each subject's head and brain. The cortical activation site was estimated by finding where the calculated electric fields best explained the coil-location dependency of the measured MTs.
The experiments and modeling showed individual variations both in the measured motor thresholds (MTs) and in the computed electric fields. When the TMS coil was moved on the scalp, the calculated electric fields in the hand knob region were shown to vary consistently with the measured MTs. Group-level analysis indicated that the electric fields were significantly correlated with the measured MTs. The strongest correlations (R = 0.69), which indicated the most likely activation site, were found in the ventral and lateral part of the hand knob. The site was independent of voluntary contractions of the target muscle.
The study showed that TMS combined with personalized electric field modeling can be used for high-resolution mapping of the motor cortex.
尽管导航和建模技术最近有了发展，但经颅磁刺激（TMS）激活的结构的类型和位置仍不清楚。
我们研究了电生理测量值与大脑中感应电场之间的关系，以定位 TMS 激活部位。
在 19 名受试者（7 名女性，12 名男性，年龄 22±4 岁）中，使用从前到内侧定向的单相 TMS 在左侧初级运动皮层（M1）的多个位置记录第一背侧骨间肌的活动和静息运动阈值。结构磁共振成像用于构建每个受试者头部和大脑的电场模型。通过寻找计算电场最能解释测量 MT 与线圈位置依赖性的位置来估计皮质激活部位。
实验和建模均显示出个体差异，表现在测量的运动阈值（MT）和计算的电场中。当 TMS 线圈在头皮上移动时，手旋钮区域的计算电场显示出与测量的 MT 一致的变化。组水平分析表明，电场与测量的 MT 显著相关。最强的相关性（R=0.69），表明最可能的激活部位，位于手旋钮的腹侧和外侧部分。该部位与目标肌肉的自愿收缩无关。
该研究表明，TMS 与个性化电场建模相结合可用于运动皮层的高分辨率映射。
