Tardelli Gabriela P, Souza Victor H, Matsuda Renan H, Garcia Marco A C, Novikov Pavel A, Nazarova Maria A, Baffa Oswaldo
Department of Physics, School of Philosophy, Science and Letters at Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
Brain Topogr. 2022 May;35(3):322-336. doi: 10.1007/s10548-022-00893-1. Epub 2022 Mar 9.
Most of the motor mapping procedures using navigated transcranial magnetic stimulation (nTMS) follow the conventional somatotopic organization of the primary motor cortex (M1) by assessing the representation of a particular target muscle, disregarding the possible coactivation of synergistic muscles. In turn, multiple reports describe a functional organization of the M1 with an overlapping among motor representations acting together to execute movements. In this context, the overlap degree among cortical representations of synergistic hand and forearm muscles remains an open question. This study aimed to evaluate the muscle coactivation and representation overlapping common to the grasping movement and its dependence on the stimulation parameters. The nTMS motor maps were obtained from one carpal muscle and two intrinsic hand muscles during rest. We quantified the overlapping motor maps in size (area and volume overlap degree) and topography (similarity and centroid Euclidean distance) parameters. We demonstrated that these muscle representations are highly overlapped and similar in shape. The overlap degrees involving the forearm muscle were significantly higher than only among the intrinsic hand muscles. Moreover, the stimulation intensity had a stronger effect on the size compared to the topography parameters. Our study contributes to a more detailed cortical motor representation towards a synergistic, functional arrangement of M1. Understanding the muscle group coactivation may provide more accurate motor maps when delineating the eloquent brain tissue during pre-surgical planning.
大多数使用导航经颅磁刺激（nTMS）的运动映射程序通过评估特定目标肌肉的代表区，遵循初级运动皮层（M1）的传统躯体定位组织，而忽略协同肌肉可能的共同激活。反过来，多篇报告描述了M1的一种功能组织，其中运动代表区相互重叠，共同作用以执行运动。在此背景下，协同的手部和前臂肌肉的皮层代表区之间的重叠程度仍是一个悬而未决的问题。本研究旨在评估抓握运动中常见的肌肉共同激活和代表区重叠及其对刺激参数的依赖性。在静息状态下，从一块腕部肌肉和两块手部固有肌获取nTMS运动图谱。我们在大小（面积和体积重叠度）和地形学（相似性和质心欧几里得距离）参数方面对重叠的运动图谱进行了量化。我们证明这些肌肉代表区高度重叠且形状相似。涉及前臂肌肉的重叠度显著高于仅在手部固有肌之间的重叠度。此外，与地形学参数相比，刺激强度对大小的影响更强。我们的研究有助于更详细地描绘M1的协同、功能排列的皮层运动代表区。在术前规划中描绘明确的脑组织时，了解肌肉群的共同激活可能会提供更准确的运动图谱。
