Activity of spinal interneurons and their effects on forearm muscles during voluntary wrist movements in the monkey
Activity of spinal interneurons and their effects on forearm muscles during voluntary wrist movements in the monkey
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DOI：
10.1152/jn.1998.80.5.2475
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发表时间：
1998-11-01
影响因子：
2.5
通讯作者：
Fetz, EE
中科院分区：
文献类型：
--
作者：
Perlmutter, SI;Maier, MA;Fetz, EE
我们研究了三只清醒猕猴的 C-6-T-1 脊髓中 577 个神经元的活动，同时它们产生视觉引导的、围绕手腕的等长弯曲/伸展扭矩。尖峰触发的肌电活动 (EMG) 平均值确定了这些单元与少于或等于 12 块前臂肌肉的相关性。一百个中间神经元产生平均峰后肌电图水平的变化，其起始潜伏期与运动神经元的单突触或寡突触连接一致；这些被分类为运动前中间神经元（PreM-IN）。大多数 PreM-IN (82%) 会在前臂肌肉中产生峰值后促进作用。早期的尖峰相关特征通常在触发尖峰之前开始，在 72 个神经元的尖峰触发平均值中可见。 64% 的 PreM-IN 的一块肌肉中存在峰后效应。与较大“肌肉场”具有不同连接的神经元通常会在协同肌肉中产生后峰值效应。 58% 的 PreM-IN 仅对屈肌有峰值后效应，29% 仅对伸肌有峰值后效应。峰值后效应在所研究的主要屈肌和伸肌中分布相对均匀。肌电图水平相对于基线的平均百分比变化以及峰后促进和峰后抑制的平均起始潜伏期相似。 PreM-IN 在产生等长手腕扭矩期间表现出多种响应模式。 24% 的 PreM-IN 的反应模式和输出效果与屈肌和伸肌控制的严格交互组织一致。对于另外 60% 的 PreM-IN，仅在一个扭矩产生方向上，活动和输出效果之间存在一致关系。这些神经元对屈曲和伸展扭矩都很活跃，其中 37 个神经元表现出放电率双向增加。观察到的相对较少数量的峰后抑制表明，当其目标肌肉被招募时，抑制性中间神经元是沉默的。与运动皮层、红核和 C-8-T-1 背根神经节中的运动前神经元相比，脊髓 PreM-IN 影响屈肌的比例更大，并且肌域更小。所有运动前群体中尖峰后促进的程度相似。 PreM-IN 常见的双向活动对于皮质运动神经元和运动前背根神经节细胞来说很少见，它们仅在其首选方向上释放扭矩。
We studied the activity of 577 neurons in the C-6-T-1 spinal cord of three awake macaque monkeys while they generated visually guided, isometric flexion/extension torques about the wrist. Spike-triggered averaging of electromyographic activity (EMG) identified the units' correlational linkages with less than or equal to 12 forearm muscles. One hundred interneurons produced changes in the level of average postspike EMG with onset latencies consistent with mono- or oligosynaptic connections to motoneurons; these were classified as premotor interneurons (PreM-INs). Most PreM-INs (82%) produced postspike facilitations in forearm muscles. Earlier spike-related features, often beginning before the trigger spike, were seen in spike-triggered averages from 72 neurons. Postspike effects were present in one muscle for 64% of the PreM-INs. Neurons with divergent linkages to larger "muscle fields" usually generated postspike effects in synergistic muscles. Fifty eight percent of the PreM-INs had postspike effects in flexor muscles only and 29% in extensor muscles only. Postspike effects were distributed relatively evenly among the primary flexor and extensor muscles studied. The mean percent change in EMG level from baseline and the mean onset latencies for postspike facilitations and postspike suppressions were similar. PreM-INs exhibited a variety of response patterns during the generation of isometric wrist torque. The response patterns and output effects of 24% of the PreM-INs were consistent with a strict reciprocal organization of flexor and extensor muscle control. For another 60% of the PreM-INs, there was a congruent relation between activity and output effects for only one direction of torque production. These neurons were active for both flexion and extension torques, including 37 neurons that exhibited bidirectional increases in discharge rate. The relatively small number of postspike suppressions observed suggests that inhibitory interneurons were silent when their target muscles were recruited. Compared with premotor neurons in the motor cortex, the red nucleus and the C-8-T-1 dorsal root ganglia, spinal PreM-INs affected flexor muscles in greater proportions and had smaller muscle fields. The magnitudes of postspike facilitations were similar in all premotor populations. Bidirectional activity, common for PreM-INs, was rare for corticomotoneuronal and premotor dorsal root ganglion cells, which discharge only for torques in their preferred direction.