McIsaac Tara L, Fuglevand Andrew J
Department of Physiology, College of Medicine, University of Arizona, P.O. Box 210093, Tucson, AZ 85721-0093, USA.
Exp Brain Res. 2008 Jun;188(1):159-64. doi: 10.1007/s00221-008-1432-7. Epub 2008 May 28.
To gain insight into the mechanism by which the nervous system orchestrates the activities of multiple muscles during voluntary motor behaviors, we measured the degree of synchrony in the discharge times across pairs of motor units recorded from two intrinsic hand muscles, the adductor pollicis (AdP) and first dorsal interosseous (FDI), in human subjects performing a precision grip. The magnitude of synchrony measured across muscles is thought to reflect the extent of divergent synaptic input delivered in common to the motor nuclei supplying the two muscles. Unlike the pronounced motor-unit synchrony observed across comparable extrinsic hand muscles during the precision grip, little synchrony was detected across these two intrinsic muscles. These results suggest that extrinsic and intrinsic muscles of the hand are controlled by descending pathways with distinctly different patterns of spinal connectivity--more widespread terminations across motor nuclei supplying extrinsic muscles whereas more focal input to individual motor nuclei innervating intrinsic muscles.
为深入了解神经系统在自主运动行为中协调多块肌肉活动的机制，我们在进行精确抓握的人类受试者中，测量了从两块手部固有肌肉（拇收肌（AdP）和第一背侧骨间肌（FDI））记录的运动单位对之间放电时间的同步程度。跨肌肉测量的同步程度被认为反映了共同传递给供应这两块肌肉的运动核的发散性突触输入的程度。与在精确抓握过程中在可比的手部外在肌肉中观察到的明显的运动单位同步不同，在这两块固有肌肉之间几乎没有检测到同步。这些结果表明，手部的外在和固有肌肉由具有明显不同脊髓连接模式的下行通路控制——供应外在肌肉的运动核有更广泛的终末，而支配固有肌肉的单个运动核有更集中的输入。
