Laboissière R, Ostry D J, Feldman A G
Institut de la Communication Parlée, Grenoble, France.
Biol Cybern. 1996 Apr;74(4):373-84. doi: 10.1007/BF00194930.
A model is presented of sagittal plane jaw and hyoid motion based on the lambda model of motor control. The model, which is implemented as a computer simulation, includes central neural control signals, position- and velocity-dependent reflexes, reflex delays, and muscle properties such as the dependence of force on muscle length and velocity. The model has seven muscles (or muscle groups) attached to the jaw and hyoid as well as separate jaw and hyoid bone dynamics. According to the model, movements result from changes in neurophysiological control variables which shift the equilibrium state of the motor system. One such control variable is an independent change in the membrane potential of alpha-motoneurons (MNs); this variable establishes a threshold muscle length (lambda) at which MN recruitment begins. Motor functions may be specified by various combinations of lambda s. One combination of lambda s is associated with the level of coactivation of muscles. Others are associated with motions in specific degrees of freedom. Using the model, we study the mapping between control variables specified at the level of degrees of freedom and control variables corresponding to individual muscles. We demonstrate that commands can be defined involving linear combinations of lambda change which produce essentially independent movements in each of the four kinematic degrees of freedom represented in the model (jaw orientation, jaw position, vertical and horizontal hyoid position). These linear combinations are represented by vectors in lambda space which may be scaled in magnitude. The vector directions are constant over the jaw/hyoid workspace and result in essentially the same motion from any workspace position. The demonstration that it is not necessary to adjust control signals to produce the same movements in different parts of the workspace supports the idea that the nervous system need not take explicit account of musculo-skeletal geometry in planning movements.
基于运动控制的拉姆达模型，提出了一个矢状面下颌和舌骨运动模型。该模型通过计算机模拟实现，包括中枢神经控制信号、与位置和速度相关的反射、反射延迟以及肌肉特性，如力对肌肉长度和速度的依赖性。该模型有七块肌肉（或肌肉群）附着在下颌和舌骨上，以及独立的下颌和舌骨动力学。根据该模型，运动是由神经生理控制变量的变化引起的，这些变化改变了运动系统的平衡状态。一个这样的控制变量是α运动神经元（MNs）膜电位的独立变化；这个变量建立了一个阈值肌肉长度（拉姆达），在这个长度时MN募集开始。运动功能可以由拉姆达的各种组合来指定。拉姆达的一种组合与肌肉的共同激活水平相关。其他组合与特定自由度的运动相关。使用该模型，我们研究了在自由度水平指定的控制变量与对应于单个肌肉的控制变量之间的映射。我们证明，可以定义涉及拉姆达变化线性组合的命令，这些命令在模型所代表的四个运动学自由度（下颌方向、下颌位置、垂直和水平舌骨位置）中的每一个中产生基本独立的运动。这些线性组合由拉姆达空间中的向量表示，其大小可以缩放。向量方向在颌/舌骨工作空间内是恒定的，并且从任何工作空间位置都会产生基本相同的运动。证明在工作空间的不同部分产生相同运动时无需调整控制信号，这支持了神经系统在规划运动时无需明确考虑肌肉骨骼几何结构的观点。
