BACKGROUND Brain mapping is fundamental to understanding brain organization and function. However, a major drawback to the traditional Brodmann parcellation technique is the reliance on the use of postmortem specimens. It has therefore historically been difficult to make any comparison regarding functional data from different regions or hemispheres within the same individual. Moreover, this method has been significant limited by subjective boundaries and classification criteria and therefore suffer from reproducibility issues. The development of transcranial magnetic stimulation (TMS) offers an alternative approach to brain mapping, specifically the motor cortical regions by eliciting quantifiable functional reactions. OBJECTIVE To precisely describe the motor cortical topographic representation of pharyngeal constrictor musculature using TMS and to further map the brain for use as a tool to study brain plasticity. METHODS 51 healthy subjects (20 male/31 female, 19-26 years old) were tested using single-pulse TMS combined with intraluminal catheter-guided high-resolution manometry and a standardized grid cap. We investigated various parameters of the motor-evoked potential (MEP) that include the motor map area, amplitude, latency, center of gravity (CoG) and asymmetry index. RESULTS Cortically evoked response latencies were similar for the left and right hemispheres at 6.79 ± 0.22 and 7.24 ± 0.27 ms, respectively. The average scalp positions (relative to the vertex) of the pharyngeal motor cortical representation were 10.40 ± 0.19 (SE) cm medio-lateral and 3.20 ± 0.20 (SE) cm antero-posterior in the left hemisphere and 9.65 ± 0.24 (SE) cm medio-lateral and 3.18 ± 0.23 (SE) cm antero-posterior in the right hemisphere. The mean motor map area of the pharynx in the left and right hemispheres were 9.22 ± 0.85(SE) cm2and 10.12 ± 1.24(SE) cm2, respectively. The amplitudes of the MEPs were 35.94 ± 1.81(SE)uV in the left hemisphere and 34.49 ± 1.95(SE)uV in the right hemisphere. By comparison, subtle but consistent differences in the degree of the bilateral hemispheric representation were also apparent both between and within individuals. CONCLUSION The swallowing musculature has a bilateral motor cortical representation across individuals, but is largely asymmetric within single subjects. These results suggest that TMS mapping using a guided intra-pharyngeal EMG catheter combined with a standardized gridded cap might be a useful tool to localize brain function/dysfunction by linking brain activation to the corresponding physical reaction.

中文翻译：

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健康受试者咽皮质表征的 TMS 脑图谱

背景大脑映射是理解大脑组织和功能的基础。然而，传统布罗德曼分割技术的一个主要缺点是依赖于死后标本的使用。因此，历史上很难对来自同一个人的不同区域或半球的功能数据进行任何比较。此外，这种方法受到主观边界和分类标准的显着限制，因此存在可重复性问题。经颅磁刺激 (TMS) 的发展为大脑映射提供了一种替代方法，特别是通过引发可量化的功能反应来绘制运动皮层区域。目的使用 TMS 精确描述咽缩肌组织的运动皮层地形表征，并进一步绘制大脑图，用作研究大脑可塑性的工具。方法 51 名健康受试者（20 名男性/31 名女性，19-26 岁）使用单脉冲 TMS 结合腔内导管引导的高分辨率测压和标准化网格帽进行测试。我们研究了运动诱发电位 (MEP) 的各种参数，包括运动图面积、振幅、潜伏期、重心 (CoG) 和不对称指数。结果左右半球的皮质诱发反应潜伏期相似，分别为 6.79 ± 0.22 和 7.24 ± 0.27 ms。咽部运动皮质表征的平均头皮位置（相对于顶点）为 10.40 ± 0.19 (SE) cm 中外侧和 3。左半球前后 20 ± 0.20 (SE) cm 和右半球 9.65 ± 0.24 (SE) cm 中外侧和 3.18 ± 0.23 (SE) cm 前后。左右半球咽部的平均运动图面积分别为 9.22 ± 0.85(SE) cm2 和 10.12 ± 1.24(SE) cm2。MEP 的振幅在左半球为 35.94 ± 1.81(SE)uV，在右半球为 34.49 ± 1.95(SE)uV。相比之下，在个体之间和个体内部，双侧半球表现程度的细微但一致的差异也很明显。结论 吞咽肌肉组织在个体之间具有双侧运动皮层表现，但在单个受试者中很大程度上是不对称的。