Computer simulations of neural mechanisms explaining upper and lower limb excitatory neural coupling.
Computer simulations of neural mechanisms explaining upper and lower limb excitatory neural coupling.
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DOI：
10.1186/1743-0003-7-59
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发表时间：
2010-12-10
影响因子：
5.1
通讯作者：
Ferris DP
中科院分区：
文献类型：
--
作者：
Huang HJ;Ferris DP
当人类进行有节奏的上肢和下肢运动样运动时，上肢用力对下肢肌肉募集有兴奋作用。为了研究这种行为观察的潜在神经机制，我们开发了计算机模拟，模拟中央模式发生器之间的肢体间神经通路。我们假设，从肢体间脊髓机制的肌肉募集的增强不足以解释在实验数据中观察到的肌肉增强水平。我们使用松冈振荡器的中央模式发生器（CPG）和确定的参数，增强振幅的节奏稳定状态的爆发。输出增强的潜在机制是兴奋性和抑制性感觉反馈增益、兴奋性和抑制性肢间耦合增益和耦合几何。我们首先模拟了最简单的情况，一个单一的CPG，然后扩展模型有两个CPG，最后四个CPG。在两个和四个CPG模型中，下肢CPG没有收到脊髓上的输入，这样，可用于增强输出的唯一机制是肢体间耦合增益和感觉反馈增益。在两个CPG模型与抑制性感觉反馈增益，只有同侧屈肌-伸肌/伸肌-屈肌耦合的兴奋性增益产生相互的上下肢爆发和增强输出高达26%。在两个CPG模型与兴奋性感觉反馈增益，对侧屈肌-屈肌/伸肌-伸肌耦合的兴奋性增益产生相互的上下肢爆发和增强输出高达100%。然而，在给定的兴奋性感觉反馈增益，由于兴奋性肢体间增益的增强只能达到20%的水平。将四个CPG互连以具有同侧屈-伸肌/伸肌-屈肌耦合、对侧屈-屈肌/伸肌-伸肌耦合和双侧屈-伸肌/伸肌-屈肌耦合，可以使运动输出增加高达32%。在实验数据中观察到的增强超过32%。在这种对称的四CPG神经结构内的增强对相对较小的肢体间耦合增益更敏感。兴奋性感觉反馈增益可以产生更大的输出幅度，但与抑制性感觉反馈增益相比，夹带需要更大的增益。基于这些模拟，对称的肢间耦合可以解释很多，但不是所有的兴奋性神经耦合之间的上肢和下肢在有节奏的运动样运动。
When humans perform rhythmic upper and lower limb locomotor-like movements, there is an excitatory effect of upper limb exertion on lower limb muscle recruitment. To investigate potential neural mechanisms for this behavioral observation, we developed computer simulations modeling interlimb neural pathways among central pattern generators. We hypothesized that enhancement of muscle recruitment from interlimb spinal mechanisms was not sufficient to explain muscle enhancement levels observed in experimental data. We used Matsuoka oscillators for the central pattern generators (CPG) and determined parameters that enhanced amplitudes of rhythmic steady state bursts. Potential mechanisms for output enhancement were excitatory and inhibitory sensory feedback gains, excitatory and inhibitory interlimb coupling gains, and coupling geometry. We first simulated the simplest case, a single CPG, and then expanded the model to have two CPGs and lastly four CPGs. In the two and four CPG models, the lower limb CPGs did not receive supraspinal input such that the only mechanisms available for enhancing output were interlimb coupling gains and sensory feedback gains. In a two-CPG model with inhibitory sensory feedback gains, only excitatory gains of ipsilateral flexor-extensor/extensor-flexor coupling produced reciprocal upper-lower limb bursts and enhanced output up to 26%. In a two-CPG model with excitatory sensory feedback gains, excitatory gains of contralateral flexor-flexor/extensor-extensor coupling produced reciprocal upper-lower limb bursts and enhanced output up to 100%. However, within a given excitatory sensory feedback gain, enhancement due to excitatory interlimb gains could only reach levels up to 20%. Interconnecting four CPGs to have ipsilateral flexor-extensor/extensor-flexor coupling, contralateral flexor-flexor/extensor-extensor coupling, and bilateral flexor-extensor/extensor-flexor coupling could enhance motor output up to 32%. Enhancement observed in experimental data exceeded 32%. Enhancement within this symmetrical four-CPG neural architecture was more sensitive to relatively small interlimb coupling gains. Excitatory sensory feedback gains could produce greater output amplitudes, but larger gains were required for entrainment compared to inhibitory sensory feedback gains. Based on these simulations, symmetrical interlimb coupling can account for much, but not all of the excitatory neural coupling between upper and lower limbs during rhythmic locomotor-like movements.