Amundsen Huffmaster Sommer L, Van Acker Gustaf M, Luchies Carl W, Cheney Paul D
University of Kansas, Bioengineering Graduate Program, Lawrence, Kansas; and.
University of Kansas Medical Center, Department of Molecular and Integrative Physiology, Kansas City, Kansas.
J Neurophysiol. 2017 Jul 1;118(1):455-470. doi: 10.1152/jn.00784.2016. Epub 2017 Apr 26.
Simplifying neuromuscular control for movement has previously been explored by extracting muscle synergies from voluntary movement electromyography (EMG) patterns. The purpose of this study was to investigate muscle synergies represented in EMG recordings associated with direct electrical stimulation of single sites in primary motor cortex (M1). We applied single-electrode high-frequency, long-duration intracortical microstimulation (HFLD-ICMS) to the forelimb region of M1 in two rhesus macaques using parameters previously found to produce forelimb movements to stable spatial end points (90-150 Hz, 90-150 μA, 1,000-ms stimulus train lengths). To develop a comprehensive representation of cortical output, stimulation was applied systematically across the full extent of M1. We recorded EMG activity from 24 forelimb muscles together with movement kinematics. Nonnegative matrix factorization (NMF) was applied to the mean stimulus-evoked EMG, and the weighting coefficients associated with each synergy were mapped to the cortical location of the stimulating electrode. Synergies were found for three data sets including ) all stimulated sites in the cortex, ) a subset of sites that produced stable movement end points, and ) EMG activity associated with voluntary reaching. Two or three synergies accounted for 90% of the overall variation in voluntary movement EMG whereas four or five synergies were needed for HFLD-ICMS-evoked EMG data sets. Maps of the weighting coefficients from the full HFLD-ICMS data set show limited regional areas of higher activation for particular synergies. Our results demonstrate fundamental NMF-based muscle synergies in the collective M1 output, but whether and how the central nervous system might coordinate movements using these synergies remains unclear. While muscle synergies have been investigated in various muscle activity sets, it is unclear whether and how synergies may be organized in the cortex. We have investigated muscle synergies resulting from high-frequency, long-duration intracortical microstimulation (HFLD-ICMS) applied throughout M1. We compared HFLD-ICMS synergies to synergies from voluntary movement. While synergies can be identified from M1 stimulation, they are not clearly related to voluntary movement synergies and do not show an orderly topographic organization across M1.
先前已通过从自愿运动肌电图（EMG）模式中提取肌肉协同作用来探索简化运动的神经肌肉控制。本研究的目的是研究与直接电刺激初级运动皮层（M1）单个部位相关的EMG记录中所代表的肌肉协同作用。我们使用先前发现能产生前肢向稳定空间终点运动的参数（90 - 150 Hz、90 - 150 μA、1000 ms刺激串长度），对两只恒河猴的M1前肢区域进行单电极高频、长时间皮层内微刺激（HFLD - ICMS）。为了全面呈现皮层输出，在M1的整个范围内系统地施加刺激。我们记录了24块前肢肌肉的EMG活动以及运动学数据。对平均刺激诱发的EMG应用非负矩阵分解（NMF），并将与每个协同作用相关的加权系数映射到刺激电极的皮层位置。在三个数据集中发现了协同作用，包括：（1）皮层中的所有刺激部位；（2）产生稳定运动终点的部位子集；（3）与自愿伸手相关的EMG活动。两到三个协同作用占自愿运动EMG总体变化的90%，而HFLD - ICMS诱发的EMG数据集则需要四到五个协同作用。来自完整HFLD - ICMS数据集的加权系数图显示，特定协同作用的较高激活区域有限。我们的结果证明了基于NMF的M1总体输出中的基本肌肉协同作用，但中枢神经系统是否以及如何利用这些协同作用来协调运动仍不清楚。虽然已经在各种肌肉活动组中研究了肌肉协同作用，但尚不清楚协同作用是否以及如何在皮层中组织。我们研究了在整个M1施加高频、长时间皮层内微刺激（HFLD - ICMS）所产生的肌肉协同作用。我们将HFLD - ICMS协同作用与自愿运动的协同作用进行了比较。虽然可以从M1刺激中识别出协同作用，但它们与自愿运动协同作用没有明显关联，并且在M1上没有显示出有序的地形组织。
