Speech function of the oropharyngeal isthmus: a modelling study

Abstract

A finite element method-based numerical model of upper airway structures (jaw, tongue, maxilla, soft palate) was implemented to observe interactions between the soft palate and tongue, and, in particular, to distinguish the contributions of individual muscles in producing speech-relevant constrictions of the oropharyngeal isthmus (OPI) or ‘uvular’ region of the oral tract. Simulations revealed a sphincter-like general operation for the OPI, particularly with regard to the function of the palatoglossus muscle. Furthermore, as has been observed with the lips, the OPI can be controlled by multiple distinct muscular mechanisms, each reliably producing a different-sized opening and robust to activation noise suggestive of modular motor control for speech. As off-midline structures of the OPI are difficult to observe during speech production, biomechanical simulation offers a promising approach to studying these structures.

Keywords::

• image-based geometric modelling
• articulatory modelling of speech
• soft palate
• oropharyngeal isthmus
• motor modularisation

Acknowledgements

The authors thank A. Ho for assistance with simulations, A. Klenin for assistance with figure preparation, and S. Bird, S. Moisik for helpful discussion.

Additional information

Funding

This work was supported by a Discovery Grant to the first author from the Natural Sciences and Engineering Research Council of Canada and by NIH [grant number DC-002717] to Haskins Laboratories.