Lowery Madeleine M, Myers Lance J, Erim Zeynep
School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Dublin, Ireland.
J Neurosci Methods. 2007 Jul 30;163(2):384-91. doi: 10.1016/j.jneumeth.2007.03.011. Epub 2007 Mar 24.
Coherence analysis is widely employed to study the correlation between discharge times of simultaneously active motor units. Despite the widespread application of the technique, it has not been fully established how the characteristics of the observed coherence are related to the properties of the shared motoneuron inputs. In addition, the exact relationship between coherence and traditional measures of motor unit synchronization remains unclear. The purpose of this study was to examine the influence of shared motoneuron inputs on coherence between motor unit discharge patterns using computer simulations. Although less sensitive to motor unit firing rates than traditional synchronization-based indices, coherence tended to decrease with increasing frequency of the common input and to increase slightly when the common input frequency was close to the motor unit firing rates. In addition, coherence tended to be highest between motor units with similar firing rates. A linear association was observed between synchronization and coherence in the 15-30 Hz range and between 'common drive' and coherence in the 0-5 Hz range. The results suggest that caution should be taken when interpreting differences in coherence observed between motor units with significantly different firing properties or when comparing data with coherence in different frequency ranges.
相干分析被广泛用于研究同时活跃的运动单位放电时间之间的相关性。尽管该技术应用广泛，但尚未完全明确观察到的相干特性如何与共享运动神经元输入的特性相关。此外，相干与运动单位同步的传统测量方法之间的确切关系仍不明确。本研究的目的是使用计算机模拟来检验共享运动神经元输入对运动单位放电模式之间相干性的影响。尽管相干性对运动单位放电频率的敏感性低于基于传统同步的指标，但随着共同输入频率的增加，相干性趋于降低，而当共同输入频率接近运动单位放电频率时，相干性会略有增加。此外，放电频率相似的运动单位之间的相干性往往最高。在15 - 30赫兹范围内，同步与相干之间以及在0 - 5赫兹范围内，“共同驱动”与相干之间均观察到线性关联。结果表明，在解释具有显著不同放电特性的运动单位之间观察到的相干差异时，或在比较不同频率范围内的相干数据时，应谨慎行事。
