Frigon Alain, Collins David F, Zehr E Paul
Neural Control of Human Movement Laboratory, Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309, USA.
J Neurophysiol. 2004 Apr;91(4):1516-23. doi: 10.1152/jn.00695.2003. Epub 2003 Dec 3.
During locomotor tasks such as walking, running, and swimming, the arms move rhythmically with the legs. It has been suggested that connections between the cervical and lumbosacral spinal cord may mediate some of this interlimb coordination. However, it is unclear how these interlimb pathways modulate reflex excitability during movement. We hypothesized that rhythmic arm movement would alter the gain of reflex pathways in the stationary leg. Soleus H-reflexes recorded during arm cycling were compared with those recorded at similar positions with the arms stationary. Nerve stimulation was delivered with the right arm at approximately 70 degrees shoulder flexion or 10 degrees shoulder extension. H-reflexes were evoked alone (unconditioned) or with sural or common peroneal nerve (CP) conditioning to decrease or increase soleus IA presynaptic inhibition, respectively. Both conditioning stimuli were also delivered with no H-reflex stimulation. H-reflex amplitudes were compared at similar M-wave amplitudes and activation levels of the soleus. Arm cycling significantly reduced (P < 0.05) unconditioned soleus H-reflexes at shoulder flexion by 21.7% and at shoulder extension by 8.8% compared with static controls. The results demonstrate a task-dependent modulation of soleus H-reflexes between arm cycling and stationary trials. Sural nerve stimulation facilitated H-reflexes at shoulder extension but not at shoulder flexion during static and cycling trials. CP nerve stimulation significantly reduced H-reflex amplitude in all conditions. Reflexes in soleus when sural and CP nerve stimulation were delivered alone, were not different between cycling and static trials; thus the task-dependent change in H reflex amplitude was not due to changes in motoneuron excitability. Therefore modulation occurred at a pre-motoneuronal level, probably by presynaptic inhibition of the IA afferent volley. Results indicate that neural networks coupling the cervical and lumbosacral spinal cord in humans are activated during rhythmic arm movement. It is proposed that activation of these networks may assist in reflex linkages between the arms and legs during locomotor tasks.
在诸如行走、跑步和游泳等运动任务中，手臂会与腿部有节奏地协同运动。有人提出，颈脊髓和腰骶脊髓之间的连接可能介导了部分这种肢体间的协调。然而，目前尚不清楚这些肢体间通路在运动过程中如何调节反射兴奋性。我们推测，有节奏的手臂运动会改变静止腿部反射通路的增益。将手臂循环运动期间记录的比目鱼肌H反射与手臂静止时在相似位置记录的H反射进行比较。在右臂处于大约70度肩屈曲或10度肩伸展时进行神经刺激。单独诱发H反射（非条件性）或用腓肠神经或腓总神经（CP）进行条件刺激，分别降低或增加比目鱼肌Ia突触前抑制。两种条件刺激也在不进行H反射刺激的情况下施加。在相似的M波幅度和比目鱼肌激活水平下比较H反射幅度。与静态对照相比，手臂循环运动显著降低（P < 0.05）了非条件性比目鱼肌H反射，肩屈曲时降低了21.7%，肩伸展时降低了8.8%。结果表明，在手臂循环运动和静止试验之间，比目鱼肌H反射存在任务依赖性调制。在静态和循环试验中，腓肠神经刺激在肩伸展时促进了H反射，但在肩屈曲时没有。CP神经刺激在所有条件下均显著降低了H反射幅度。单独施加腓肠神经和CP神经刺激时，比目鱼肌的反射在循环运动和静态试验之间没有差异；因此，H反射幅度的任务依赖性变化不是由于运动神经元兴奋性的改变。因此，调制发生在运动神经元前水平，可能是通过对Ia传入冲动的突触前抑制。结果表明，人类中连接颈脊髓和腰骶脊髓的神经网络在有节奏的手臂运动期间被激活。有人提出，这些神经网络的激活可能有助于在运动任务期间手臂和腿部之间的反射联系。
