Decorrelating actions of renshaw interneurons on the firing of spinal motoneurons within a motor nucleus: A simulation study
Decorrelating actions of renshaw interneurons on the firing of spinal motoneurons within a motor nucleus: A simulation study
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DOI：
10.1152/jn.1998.80.1.309
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发表时间：
1998-07-01
影响因子：
2.5
通讯作者：
Rymer, WZ
中科院分区：
文献类型：
--
作者：
Maltenfort, MG;Heckman, CJ;Rymer, WZ
建立了脊髓运动神经元和Renshaw细胞的模拟模型，以研究复发性抑制的可能功能。已知通过Renshaw细胞的反复抑制反馈是弱的。在我们的模型中，与此一致，运动神经元放电每秒仅减少几个脉冲。我们最初的假设是，Renshaw细胞会抑制由共享的动态输入引起的运动神经元的同步放电。每个运动神经元在其输入中接收相同的噪声模式。同步系数被定义为相对于选定的参考运动神经元的活动的平均运动神经元群体放电;如果运动神经元群体在参考运动神经元活跃的同时特别活跃，则产生正系数。有或没有复发性抑制，运动神经元池往往很少，如果有的话同步。预期复发性抑制会进一步降低同步性。相反，它降低了同步系数的方差，对平均值没有可比的影响。令人惊讶的是，运动神经元之间的正相关和负相关都被反复抑制所抑制。简而言之，复发性抑制可能作为一种负反馈机制，使由共同输入连接的运动神经元去相关。这种去相关的后果是抑制频谱活动，显然是由于共同的兴奋性驱动相关的运动神经元放电。没有经常性的抑制，总运动神经元池发射的功率谱显示了一个峰值，对应于最大的测量发射率的运动神经元在池中的频率。复发性抑制减少或消除了这个峰值，大概是通过最大限度地减少池元素之间的相关发射的可能性。Renshaw细胞可以通过从运动神经元的聚集活动中去除振荡成分来减少生理性震颤。在高于“同步”峰值频率的频率下，复发性抑制也改善了运动神经元输出和共同驱动之间的一致性。敏感性分析表明，频谱效应变得更强的抑制性突触电导的持续时间缩短，无论是幅度或抑制电导的空间范围增加，以保持恒定的净抑制。总的来说，Renshaw抑制似乎是一种强大的方式来调整神经元群体的动态行为，对其静态增益的影响最小。
A simulation of spinal motoneurons and Renshaw cells was constructed to examine possible functions of recurrent inhibition. Recurrent inhibitory feedback via Renshaw cells is known to be weak. In our model, consistent with this, motoneuron firing was only reduced by a few pulses per second. Our initial hypothesis was that Renshaw cells would suppress synchronous firings of motoneurons caused by shared, dynamic inputs. Each motoneuron received an identical pattern of noise in its input. Synchrony coefficients were defined as the average motoneuron population firing relative to the activity of selected reference motoneurons; positive coefficients resulted if the motoneuron population was particularly active at the same time the reference motoneuron was active. With or without recurrent inhibition, the motoneuron pools tended to show little if any synchronization. Recurrent inhibition was expected to reduce the synchrony even further. Instead, it reduced the variance of the synchrony coefficients, without a comparable effect on the average. This suggests-surprisingly-that both positive and negative correlations between motoneurons are suppressed by recurrent inhibition. In short, recurrent inhibition may operate as a negative feedback mechanism to decorrelate motoneurons linked by common inputs. A consequence of this decorrelation is the suppression of spectral activity that apparently arises from correlated motoneuron firings due to common excitatory drive. Without recurrent inhibition, the power spectrum of the total motoneuron pool firings showed a peak at a frequency corresponding to the largest measured firing rates of motoneurons in the pool. Recurrent inhibition either reduced or abolished this peak, presumably by minimizing the likelihood of correlated firing among pool elements. Renshaw cells may act to diminish physiological tremor, by removing oscillatory components from aggregate motoneuron activity. Recurrent inhibition also improved coherence between the aggregate motoneuron output and the common drive, at frequencies above the frequency of the "synchronous" peak. Sensitivity analyses demonstrated that the spectral effect became stronger as the duration of inhibitory synaptic conductance was shortened with either the magnitude or the spatial extent of the inhibitory conductances increased to maintain constant net inhibition. Overall, Renshaw inhibition appears to be a powerful way to adjust the dynamic behavior of a neuron population with minimal impact on its static gain.