Department of Clinical Neurophysiology, Kuopio University Hospital, Finland.
Hum Brain Mapp. 2010 Aug;31(8):1272-80. doi: 10.1002/hbm.20942.
Navigated transcranial magnetic stimulation (TMS) can be used to stimulate functional cortical areas at precise anatomical location to induce measurable responses. The stimulation has commonly been focused on anatomically predefined motor areas: TMS of that area elicits a measurable muscle response, the motor evoked potential. In clinical pathologies, however, the well-known homunculus somatotopy theory may not be straightforward, and the representation area of the muscle is not fixed. Traditionally, the anatomical locations of TMS stimulations have not been reported at the group level in standard space. This study describes a methodology for group-level analysis by investigating the normal representation areas of thenar and anterior tibial muscle in the primary motor cortex. The optimal representation area for these muscles was mapped in 59 healthy right-handed subjects using navigated TMS. The coordinates of the optimal stimulation sites were then normalized into standard space to determine the representation areas of these muscles at the group-level in healthy subjects. Furthermore, 95% confidence interval ellipsoids were fitted into the optimal stimulation site clusters to define the variation between subjects in optimal stimulation sites. The variation was found to be highest in the anteroposterior direction along the superior margin of the precentral gyrus. These results provide important normative information for clinical studies assessing changes in the functional cortical areas because of plasticity of the brain. Furthermore, it is proposed that the presented methodology to study TMS locations at the group level on standard space will be a suitable tool for research purposes in population studies.
经颅磁刺激（TMS）可用于刺激精确解剖位置的功能皮质区，以产生可测量的反应。这种刺激通常集中在解剖上预先定义的运动区：该区域的 TMS 会引起可测量的肌肉反应，即运动诱发电位。然而，在临床病理学中，众所周知的同身论躯体定位理论可能并不直接，肌肉的代表区域并不固定。传统上，TMS 刺激的解剖位置在标准空间中没有在群体水平上进行报告。本研究通过研究初级运动皮层中鱼际肌和胫骨前肌的正常代表区域，描述了一种用于群体水平分析的方法。使用导航 TMS 对 59 名健康右利手受试者进行研究，以确定这些肌肉的最佳代表区域。然后将最佳刺激部位的坐标归一化为标准空间，以确定健康受试者群体水平上这些肌肉的代表区域。此外，将 95%置信区间椭球拟合到最佳刺激部位簇中，以定义最佳刺激部位之间的受试者间变异性。发现这种变异性在前后方向上沿着中央前回的上缘最高。这些结果为评估大脑可塑性引起的功能皮质区变化的临床研究提供了重要的规范信息。此外，本文提出的在标准空间上研究 TMS 位置的群体水平的方法将是人群研究中研究目的的合适工具。
