Salenius S, Portin K, Kajola M, Salmelin R, Hari R
Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland.
J Neurophysiol. 1997 Jun;77(6):3401-5. doi: 10.1152/jn.1997.77.6.3401.
We recorded whole scalp magnetoencephalographic (MEG) signals simultaneously with the surface electromyogram from upper and lower limb muscles of six healthy right-handed adults during voluntary isometric contraction. The 15- to 33-Hz MEG signals, originating from the anterior bank of the central sulcus, i.e., the primary motor cortex, were coherent with motor unit firing in all subjects and for all muscles. The coherent cortical rhythms originated in the hand motor area for upper limb muscles (1st dorsal interosseus, extensor indicis proprius, and biceps brachii) and close to the foot area for lower limb muscles (flexor hallucis brevis). The sites of origin corresponding to different upper limb muscles did not differ significantly. The cortical signals preceded motor unit firing by 12-53 ms. The lags were shortest for the biceps brachii and increased systematically with increasing corticomuscular distance. We suggest that the motor cortex drives the spinal motoneuronal pool during sustained contractions, with the observed cortical rhythmic activity influencing the timing of efferent commands. The cortical rhythms could be related to motor binding, but the rhythmic output may also serve to optimize motor cortex output during isometric contractions.
我们在六名健康右利手成年人进行自主等长收缩期间，同时记录了全头皮脑磁图（MEG）信号以及上肢和下肢肌肉的表面肌电图。起源于中央沟前缘（即初级运动皮层）的15至33赫兹MEG信号，在所有受试者和所有肌肉中均与运动单位放电相关。对于上肢肌肉（第一背侧骨间肌、示指固有伸肌和肱二头肌），相干皮质节律起源于手部运动区；对于下肢肌肉（拇短屈肌），相干皮质节律起源于靠近足部的区域。对应于不同上肢肌肉的起源部位没有显著差异。皮质信号比运动单位放电提前12 - 53毫秒。肱二头肌的延迟最短，并随着皮质 - 肌肉距离的增加而系统性增加。我们认为，在持续收缩过程中，运动皮层驱动脊髓运动神经元池，观察到的皮质节律性活动影响传出指令的时间。皮质节律可能与运动整合有关，但节律性输出也可能有助于在等长收缩期间优化运动皮层的输出。
