Control Principle of Motor Units in Neuro-Muscular Systems

为了使瘫痪运动功能的FES恢复更加合理，需要建立非线性、时变的肌肉收缩动力学模型。我们建立了一个激活模型，侧重于钙从肌浆网释放和重新封存到肌浆网中，包括钙诱导的钙释放。该模型存在钙离子浓度的两个稳定平衡点。从低平衡点到高平衡点的变化可以由高频输入脉冲序列产生，这将解释增强作用。该模型还显示了一种类似捕捉的效应，即施加单一脉冲后肌力持续增加。我们还开发了一种从噪声信号中检测神经动作电位(AP)的方法。这种方法可以应用于肌电的分解，肌电是来自运动单位的动作电位的总体。对低信噪比条件下的AP进行多分辨率分析。多变量分析用于从多个单位的活动记录中估计单个单位的活动。由单个单元产生的AP具有取决于诸如光纤的大小和光纤与记录电极之间的距离等因素的特征波形。因此，AP根据其波形被划分为每个单元。

To make the FES-restoration of paralyzed motor function more rational, it is required that the nonlinear and time-variant muscle contraction dynamics is modeled. We built an activation model with emphasis on the calcium liberation from and re-sequestration into the sarcoplasmic reticulum, including calcium-induced calcium release. The model had two stable equilibrium points in the calcium concentration. Changes from the low to the high equilibrium point could be produced by high frequency trains of input pulses and would account for the potentiation. The model also showed a catch-like effect, as a long-lasting increment of muscle force after the application of single pulse.We also developed a method for detecting nerve action potentials (APs) from noisy signals. This method can be applied to the decomposition of electro-myograms, which are the population of action potentials from motor units. Multiresolution analysis was used for detecting APs under low SNR condition. Multivariate analysis was used to estimate single-unit activity from multi-unit activity recordings. APs produced by an individual unit have a characteristic waveform depending on factors such as the size of the fiber and the distance between the fiber and the recording electrode. Therefore, APs were classified into each unit based on their waveforms.