An MRI analysis of the extrinsic tongue muscles during vowel production

Functions of the extrinsic tongue muscles in vowel production were examined by measurements of muscle length and tongue tissue deformation using MRI (magnetic resonance imaging). Results from the analysis of Japanese vowel data suggested: (1) Contraction and relaxation of the three subdivisions of the genioglossus (GG) play a dominant role in forming tongue shapes for vowels. (2) The extra-lingual part of the styloglossus (SG), which was previously thought to cause a high-back tongue position by pulling its insertion point in the tongue, was found to be nearly constant across all vowels both in length and orientation. (3) The tongue shape for back vowels is mainly achieved by internal deformation of the tongue tissue, and the medial tissue of the tongue showed lateral expansion in front vowels, and medial compression in back vowels.