Cody F W, Plant T
Department of Physiological Sciences, University of Manchester, U.K.
Exp Brain Res. 1989;78(3):613-23. doi: 10.1007/BF00230249.
Reciprocal inhibition of the voluntarily contracting wrist extensor (extensor carpi radialis, ECR) evoked by proprioceptive afferent input from the flexor (flexor carpi radialis, FCR), was studied in healthy human subjects. Vibration of the FCR tendon was used to elicit Ia-dominated afferent discharge whilst inhibition of ECR was assessed as the reduction in asynchronous, on-going EMG. A small early phase of inhibition (I1) was evident in 25% of trials. The latency (ca. 25 ms) of this component suggested that it was mediated by an Ia oligosynaptic. possibly 'classical' disynaptic, inhibitory pathway. A later and apparently separate phase of reduced activity (I2, ca. 40 ms) was, however, far more consistently observed (96% of trials) and of greater magnitude. The I2 component was usually followed, some 20 ms later, by a phase of elevated activity (E1, 72% trials). Reductions in simultaneously recorded net extensor torque commenced at about 60 ms following the onset of flexor tendon vibration, i.e. some 20 ms after the main I2 EMG component. These mechanical responses must have almost exclusively resulted from reciprocal inhibition of extensor EMG since vibration of the relaxed FCR evoked minimal excitatory flexor activity. The reflex pattern, in any individual subject, was relatively unaffected by altering the duration of the vibration train between one and nineteen cycles (125 Hz). This suggests that the entire response complex resulted largely from the initial afferent volley. The sizes of both the I1 and I2 reductions in ECR activity increased with increasing voluntary extensor contraction so that their depths remained constant proportions of background EMG. Very similar results were obtained when reciprocal inhibition of FCR was produced by vibration of the belly of ECR. Thus, reciprocal inhibition between wrist muscles is mainly expressed as a rather stereotyped, short duration reduction in EMG whose depth is determined by the pre-existing level of motor activity. Some functional implications of this form of reflex behaviour are discussed.
在健康人体受试者中，研究了来自屈肌（桡侧腕屈肌，FCR）的本体感觉传入输入对主动收缩的腕伸肌（桡侧腕长伸肌，ECR）的交互抑制作用。通过FCR肌腱振动来引发以Ia类为主的传入放电，而ECR的抑制则通过异步进行中的肌电图（EMG）的减少来评估。在25%的试验中，出现了一个小的早期抑制阶段（I1）。该成分的潜伏期（约25毫秒）表明它是由Ia类少突触介导的。可能是“经典”的双突触抑制途径。然而，随后出现的一个明显不同的活动降低阶段（I2，约40毫秒）被更一致地观察到（96%的试验）且幅度更大。I2成分通常在约20毫秒后，紧接着出现一个活动增强阶段（E1，72%试验）。在屈肌肌腱振动开始后约60毫秒，即主要的I2 EMG成分出现约20毫秒后，同时记录的净伸肌扭矩开始降低。这些机械反应几乎肯定完全是由于伸肌EMG的交互抑制引起的，因为放松的FCR振动引发的屈肌兴奋活动极小。在任何个体受试者中，通过改变振动序列在1至19个周期（125赫兹）之间的持续时间，反射模式相对不受影响。这表明整个反应复合体很大程度上是由最初的传入冲动引发的。随着主动伸肌收缩增加，ECR活动的I1和I2降低幅度均增大，因此它们的深度与背景EMG保持恒定比例。当通过ECR肌腹振动产生FCR的交互抑制时，也获得了非常相似的结果。因此，腕部肌肉之间的交互抑制主要表现为EMG中一种相当刻板、持续时间短的降低，其深度由预先存在的运动活动水平决定。讨论了这种反射行为形式的一些功能意义。
