A four-cube FEM model of the extrinsic and intrinsic tongue muscles to simulate the production of vowel /i/

Roles of the extrinsic and intrinsic tongue muscles in the production of vowel /i/ were examined using a finite element model applied to the tagged cine-MRI data. It has been thought that tongue tissue deformation for /i/ is mainly due to the combined actions of the genioglossus muscle bundles advancing the tongue root to elevate the dorsum with a mid-line grooving. A recent study with the tagging-MRI revealed an independent hydrostat factor of the anterior half of the tongue during /ei/ sequence: elevation of the tongue blade was caused by medial tissue compression with earlier, faster and greater tissue deformation. This result indicates that the contraction of the genioglossus is not a single factor to account for the vowel /i/ and implies that the intrinsic tongue muscles also contribute to tongue deformation to produce the vowel. In this study, a simple four-cube model was build to examine co-contraction effect of the genioglossus and transverse muscles using finite element method (FEM). The simulation result with the anterior transverse muscle (Ta) showed a good agreement with the taggingMRI data, suggesting that transverse anterior also plays an important role for the production of the vowel /i/.