Absence of postural muscle synergies for balance after spinal cord transection
Absence of postural muscle synergies for balance after spinal cord transection
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DOI：
10.1152/jn.00038.2013
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发表时间：
2013-09-01
影响因子：
2.5
通讯作者：
Ting, Lena H.
中科院分区：
文献类型：
--
作者：
Chvatal, Stacie A.;Macpherson, Jane M.;Ting, Lena H.
尽管经过脊柱化的猫也可以被训练在完全重量支撑下站立和行走，但对扰动的定向适当的长潜伏反应受到损害，这表明这些行为是由不同的神经机制介导的。然而，目前尚不清楚这些反应是否反映了使用适当的肌肉协调模式来保持平衡的姿势反应减弱，或者是由于根本不同的神经机制（例如肌肉协同收缩或短潜伏期拉伸反应增加）造成的。在这里，我们对之前收集的数据进行了肌肉协同分析，以确定脊柱化后动物体内平衡肌肉活动的空间组织是否发生变化。我们假设用于平衡控制的肌肉活动的模块化组织被脊髓横断破坏。在四只动物中，通过非负矩阵分解从脊柱化之前和之后的姿势肌肉活动中提取肌肉协同作用。三只动物的肌肉协同数在脊柱化后减少，而一只动物的肌肉协同数增加。然而，脊髓化后，肌肉协同结构发生了很大改变，方向调整减少，表明肌肉活动的组织几乎没有一致性。此外，在完整但未脊柱化的情况下，肌肉协同募集与随后的力量产生相关。我们的结果表明，平衡控制的感觉运动反馈反应的模块化结构在脊髓化后被严重破坏，这表明平衡控制的肌肉协同作用不能仅通过脊髓回路来实现。此外，我们证明了重量支撑背后的脊柱机制与方向平衡控制背后的脑干机制不同。
Although cats that have been spinalized can also be trained to stand and step with full weight support, directionally appropriate long-latency responses to perturbations are impaired, suggesting that these behaviors are mediated by distinct neural mechanisms. However, it remains unclear whether these responses reflect an attenuated postural response using the appropriate muscular coordination patterns for balance or are due to fundamentally different neural mechanisms such as increased muscular cocontraction or short-latency stretch responses. Here we used muscle synergy analysis on previously collected data to identify whether there are changes in the spatial organization of muscle activity for balance within an animal after spinalization. We hypothesized that the modular organization of muscle activity for balance control is disrupted by spinal cord transection. In each of four animals, muscle synergies were extracted from postural muscle activity both before and after spinalization with nonnegative matrix factorization. Muscle synergy number was reduced after spinalization in three animals and increased in one animal. However, muscle synergy structure was greatly altered after spinalization with reduced direction tuning, suggesting little consistent organization of muscle activity. Furthermore, muscle synergy recruitment was correlated to subsequent force production in the intact but not spinalized condition. Our results demonstrate that the modular structure of sensorimotor feedback responses for balance control is severely disrupted after spinalization, suggesting that the muscle synergies for balance control are not accessible by spinal circuits alone. Moreover, we demonstrate that spinal mechanisms underlying weight support are distinct from brain stem mechanisms underlying directional balance control.