Spinal circuits mediate a stretch reflex between the upper limbs in humans
Spinal circuits mediate a stretch reflex between the upper limbs in humans
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DOI：
10.1016/j.neuroscience.2020.02.007
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发表时间：
2020-02
期刊：
影响因子：
3.3
通讯作者：
T. Muraoka;I. Kurtzer
中科院分区：
文献类型：
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作者：
T. Muraoka;I. Kurtzer
肢体间反射在协调不同肢体的行为中起着重要作用。先前的研究表明，人类肘部肌肉在长潜伏期（50-100 ms）表达肢体间拉伸反射，这与跨皮质联系的时间一致。在这里，我们探索在人类参与者的肩膀肌肉的肢体间伸展反射。意想不到的扭矩脉冲位移了一个或两个肩膀，而参与者采取稳定的姿势对抗背景扭矩。结果表明，在短潜伏期内，肩胛伸肌和屈肌都发生了肢间拉伸反射；快速计时（36-50 毫秒）必须涉及两个手臂的脊柱联动。在长潜伏期也观察到肢体间伸展反射，但与之前的短潜伏期相反；当短潜伏期拉伸反射为兴奋性时，长潜伏期拉伸反射为抑制性，反之亦然。对比对侧手臂移位和双臂同时移位时的反应，发现抑制性肢体间伸展反射不依赖于肢体内伸展反射，而兴奋性肢体间伸展反射受到肢体内伸展反射的抑制。我们的研究结果首次证明了人类上肢的短潜伏期肢体间拉伸反射，并揭示了肢体内和肢体间拉伸反射的相互作用的脊髓回路。
Inter-limb reflexes play an important role in coordinating behaviors involving different limbs. Previous studies have demonstrated that human elbow muscles express an inter-limb stretch reflex at long-latency (50–100 ms), a timing consistent with a trans-cortical linkage. Here we probe for inter-limb stretch reflexes in the shoulder muscles of human participants. Unexpected torque pulses displaced one or both shoulders while participants adopted a steady posture against background torques. The results demonstrated inter-limb stretch reflexes occurring at short-latency for both shoulder extensors and flexors; the rapid timing (36–50 ms) must involve a spinal linkage for the two arms. Inter-limb stretch reflexes were also observed at long-latency yet they were opposite to the preceding short-latency; when the short-latency stretch reflex was excitatory then the long-latency stretch reflex was inhibitory and vice versa. Comparing the responses to contralateral arm displacement to those during simultaneous displacement of both arms revealed that inhibitory inter-limb stretch reflexes are independent of within-limb stretch reflexes, but that excitatory inter-limb stretch reflexes are suppressed by within-limb stretch reflexes. Our results provide the first demonstration of short-latency inter-limb stretch reflexes in the upper limb of humans and reveal interacting spinal circuits for within-limb and inter-limb stretch reflexes.