The comparable size and overlapping nature of upper limb distal and proximal muscle representations in the human motor cortex
The comparable size and overlapping nature of upper limb distal and proximal muscle representations in the human motor cortex
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DOI：
10.1111/j.1460-9568.2006.04760.x
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发表时间：
2006-05-01
影响因子：
3.4
通讯作者：
Capaday, Charles
中科院分区：
文献类型：
--
作者：
Devanne, Herve;Cassim, Francois;Capaday, Charles
本研究的目的是确定近端和远端上肢肌肉代表在人类运动皮层的相对大小和位置。经颅磁刺激诱发的运动诱发电位（MEP）记录在近端前三角肌（AD）和远端桡侧腕伸肌（ECR）和第一骨间背侧肌（1DI）。线圈沿放置在受试者头部的紧密贴合的聚酯帽上绘制的网格以1 cm沿着的步长移动。在每个位置，以1.2倍的主动运动阈值（AMT）提供四个刺激，并实时平均MEP。在每个刺激部位测量每块肌肉的平均MEP的峰-峰振幅。通过像素计数算法测量肌肉的代表面积。通过将3D洛伦兹函数拟合到数据点来确定每个肌肉的面积表示的最佳点，其对应于获得最大MEP的轨迹附近。远侧肌群的最适点比近侧肌群的最适点位于运动带的沿着。然而，面积表征的大小之间没有统计学显著差异，并且它们相当大地重叠。此外，在另外5名受试者中，使用放置在超焦点方向的45 mm小线圈，以最低阈值（通常为1DI）的肌肉AMT的1.1-1.15倍刺激强度获得标测图。即使在这种非常严格的条件下，AD，ECR和1DI的映射表示重叠，尽管边界之间的明显分界线也很明显。这些观察结果表明，刺激传播本身并不能解释肌肉表征的重叠。这些结果表明，常用的近端和远端上肢肌肉，单独采取，控制的运动皮层领土的大小大致相等，显着重叠，尽管在其最佳点的位置的差异。
The purpose of this study was to determine the relative size and location of proximal and distal upper limb muscle representations in the human motor cortex. Motor-evoked potentials (MEPs) evoked by transcranial magnetic stimulation were recorded in the proximal muscle anterior deltoid ( AD) and in the distal muscles extensor carpi radialis (ECR) and first dorsal interosseus (1DI). The coil was moved in steps of 1 cm along a grid drawn on a tight-fitting polyester cap placed on the subject's head. At each location, four stimuli were delivered at 1.2 times the active motor threshold (AMT), and MEPs averaged in real-time. The peak-to-peak amplitude of each muscle's mean MEP was measured at each stimulation site. The area of a muscle's representation was measured by a pixel-counting algorithm. The optimal point of each muscle's areal representation, which corresponds to the locus near which the largest MEPs are obtained, was determined by fitting a 3D Lorentzian function to the data points. The optimal point of distal muscles tended to be situated more laterally along the motor strip than that of proximal muscles. However, there was no statistically significant difference between the size of the areal representations and they overlapped considerably. Additionally, in another five subjects, using a small 45-mm coil placed in a hyper-focal orientation, maps were obtained at a stimulus intensity of 1.1-1.15 times the AMT of the muscle with the lowest threshold, usually the 1DI. Even in this very stringent condition, the mapped representations of the AD, ECR and 1DI overlapped, notwithstanding that sharp demarcations between borders were also apparent. These observations demonstrate that stimulus spread alone does not explain the overlap of muscle representations. These results show that commonly used proximal and distal upper-limb muscles, taken individually, are controlled by motor cortical territories of approximately equal size that significantly overlap despite differences in the location of their optimal points.