Sanguineti V, Laboissière R, Payan Y
Dipartimento di Informatica, Sistemistica e Telematica, Università di Genova, Italy.
Biol Cybern. 1997 Jul;77(1):11-22. doi: 10.1007/s004220050362.
Tongue movements during speech production have been investigated by means of a simple yet realistic biomechanical model, based on a finite elements modeling of soft tissues, in the framework of the equilibrium point hypothesis (lambda-model) of motor control. In particular, the model has been applied to the estimation of the "central" control commands issued to the muscles, for a data set of mid-sagittal digitized tracings of vocal tract shape, recorded by means of low-intensity X-ray cineradiographies during speech. In spite of the highly non-linear mapping between the shape of the oral cavity and its acoustic consequences, the organization of control commands preserves the peculiar spatial organization of vowel phonemes in acoustic space. A factor analysis of control commands, which have been decomposed into independent or "orthogonal" muscle groups, has shown that, in spite of the great mobility of the tongue and the highly complex arrangement of tongue muscles, its movements can be explained in terms of the activation of a small number of independent muscle groups, each corresponding to an elementary or "primitive" movement. These results are consistent with the hypothesis that the tongue is controlled by a small number of independent "articulators", for which a precise biomechanical substrate is provided. The influence of the effect of jaw and hyoid movements on tongue equilibrium has also been evaluated, suggesting that the bony structures cannot be considered as a moving frame of reference, but, indeed, there may be a substantial interaction between them and the tongue, that may only be accounted for by a "global" model. The reported results also define a simple control model for the tongue and, in analogy with similar modelling studies, they suggest that, because of the peculiar geometrical arrangement of tongue muscles, the central nervous system (CNS) may not need a detailed representation of tongue mechanics but rather may make use of a relatively small number of muscle synergies, that are invariant over the whole space of tongue configurations.
在运动控制的平衡点假设（λ模型）框架下，基于软组织的有限元建模，通过一个简单而逼真的生物力学模型，对言语产生过程中的舌运动进行了研究。具体而言，该模型已应用于估计向肌肉发出的“中枢”控制指令，该数据集来自于在言语过程中通过低强度X射线电影摄影记录的声道形状的矢状面数字化描记。尽管口腔形状与其声学结果之间存在高度非线性映射，但控制指令的组织在声学空间中保留了元音音素独特的空间组织。对已分解为独立或“正交”肌肉群的控制指令进行的因子分析表明，尽管舌头具有很大的灵活性且舌肌排列高度复杂，但其运动可以用少量独立肌肉群的激活来解释，每个肌肉群对应于一个基本或“原始”运动。这些结果与舌头由少量独立“发音器”控制的假设一致，为此提供了精确的生物力学基础。还评估了下颌和舌骨运动对舌平衡的影响，这表明骨骼结构不能被视为一个移动的参考框架，但实际上它们与舌头之间可能存在实质性相互作用，这可能只能通过一个“全局”模型来解释。报告的结果还定义了一个简单的舌头控制模型，并且与类似的建模研究类似，它们表明，由于舌肌独特的几何排列，中枢神经系统（CNS）可能不需要详细表示舌头力学，而是可以利用相对少量的肌肉协同作用，这些协同作用在舌头配置的整个空间中是不变的。
