Hikita Keigo, Gomez-Tames Jose, Hirata Akimasa
Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Aichi, Japan.
Center for Frontier Medical Engineering, Chiba University, Chiba 263-8522, Chiba, Japan.
Brain Sci. 2023 Jan 9;13(1):116. doi: 10.3390/brainsci13010116.
Transcranial magnetic stimulation (TMS) activates brain cells in a noninvasive manner and can be used for mapping brain motor functions. However, the complexity of the brain anatomy prevents the determination of the exact location of the stimulated sites, resulting in the limitation of the spatial resolution of multiple targets. The aim of this study is to map two neighboring muscles in cortical motor areas accurately and quickly. Multiple stimuli were applied to the subject using a TMS stimulator to measure the motor-evoked potentials (MEPs) in the corresponding muscles. For each stimulation condition (coil location and angle), the induced electric field (EF) in the brain was computed using a volume conductor model for an individualized head model of the subject constructed from magnetic resonance images. A post-processing method was implemented to determine a TMS hotspot using EF corresponding to multiple stimuli, considering the amplitude of the measured MEPs. The dependence of the computationally estimated hotspot distribution on two target muscles was evaluated ( = 11). The center of gravity of the first dorsal interosseous cortical representation was lateral to the abductor digiti minimi by a minimum of 2 mm. The localizations were consistent with the putative sites obtained from previous EF-based studies and fMRI studies. The simultaneous cortical mapping of two finger muscles was achieved with only several stimuli, which is one or two orders of magnitude smaller than that in previous studies. Our proposal would be useful in the preoperative mapping of motor or speech areas to plan brain surgery interventions.
经颅磁刺激（TMS）以非侵入性方式激活脑细胞，可用于绘制脑运动功能图。然而，脑解剖结构的复杂性阻碍了对受刺激部位精确位置的确定，导致多个靶点空间分辨率受限。本研究的目的是准确、快速地绘制皮质运动区中两块相邻肌肉的图谱。使用TMS刺激器对受试者施加多次刺激，以测量相应肌肉中的运动诱发电位（MEP）。对于每种刺激条件（线圈位置和角度），利用基于磁共振图像构建的受试者个体化头部模型的容积导体模型计算大脑中的感应电场（EF）。实施一种后处理方法，考虑测量的MEP的幅度，使用与多次刺激对应的EF来确定TMS热点。评估了计算估计的热点分布对两块目标肌肉的依赖性（n = 11）。第一背侧骨间肌皮质代表区的重心比小指展肌外侧至少2毫米。这些定位与先前基于EF的研究和功能磁共振成像研究获得的假定部位一致。仅通过几次刺激就实现了对两块手指肌肉的同时皮质映射，这比先前研究中的次数小一到两个数量级。我们的方法将有助于在术前绘制运动或言语区域图谱，以规划脑部手术干预。
