Schmied A, Vedel J P, Calvin-Figuière S, Rossi-Durand C, Pagni S
C.N.R.S.-N.B.M., Marseille, France.
Electroencephalogr Clin Neurophysiol. 1997 Jun;105(3):220-34. doi: 10.1016/s0924-980x(97)00015-5.
The task-dependence of homonymous muscle afferent inputs was investigated in motor units of the extensor carpi radialis muscles during voluntary isometric contraction involving either the activation of agonist extensor muscles (wrist extension) or the co-activation of antagonist extensor and flexor muscles (hand clenching). The effectiveness of the muscle afferent monosynaptic inputs was tested by delivering either tendon taps or electrical stimulation to the radial nerve. In both cases, the motor unit responses, which took the form of narrow peaks in the peri-stimulus time histograms, were found to be significantly greater during hand clenching. The parallel enhancement of the responses to both mechanical and electrical stimulations observed during hand clenching could not be explained in terms of changes in the muscle spindle responsiveness. The enhancement of the motor units' responsiveness was apparent during the first 0.5 ms of the peaks in the peri-stimulus time histograms, taken to be uncontaminated by any polysynaptic components. It may therefore have reflected an increase in the amplitude of the excitatory monosynaptic potentials generated by the muscle spindle primary afferents. This is interpreted in terms of changes in the presynaptic inhibition, which might be depressed as the result of the large-scale activation of palm and finger cutaneous afferents liable to occur during hand clenching.
在涉及主动肌伸肌激活（腕伸展）或拮抗肌伸肌与屈肌共同激活（手握拳）的随意等长收缩过程中，研究了桡侧腕伸肌运动单位中同名肌传入输入的任务依赖性。通过对桡神经进行肌腱轻敲或电刺激来测试肌肉传入单突触输入的有效性。在这两种情况下，运动单位反应在刺激周围时间直方图中表现为窄峰形式，发现在握拳时明显更大。在握拳过程中观察到的对机械和电刺激反应的平行增强，无法用肌梭反应性的变化来解释。运动单位反应性的增强在刺激周围时间直方图的峰值的前0.5毫秒内很明显，这被认为没有受到任何多突触成分的影响。因此，它可能反映了肌梭初级传入纤维产生的兴奋性单突触电位幅度的增加。这可以用突触前抑制的变化来解释，突触前抑制可能由于握拳时手掌和手指皮肤传入纤维的大规模激活而受到抑制。
