Consideration of Muscle C Physiological Articu

Physiological models of the speech organs must consider cocontraction of the muscles, a common phenomenon taking place during articulation. This study investigated cocontraction of the tongue muscles using the physiological articulatory model that replicates midsagittal regions of the speech organs to simulate articulatory movements during speech [1,2]. The relation between the muscle force and tongue movement obtained by the model simulation indicated that each muscle drives the tongue towards an equilibrium position (EP) corresponding to the magnitude of the activation forces. Contributions of the muscles to the tongue movement were evaluated by the distance between the equilibrium positions. Based on the EPs and the muscle contributions, an invariant mapping (the EP map) was established to function the connection of a spatial location to a muscle force. Cocontractions between agonist and antagonist muscles were simulated using the EP maps. The simulations demonstrated that coarticulation with multiple targets could be compatibly realized using the co-contraction mechanism. The implementation of the co-contraction mechanism enables relatively independent control over the tongue tip and body.