Functional anatomy of the human tongue: Review and implications for the development of speech production.

To acquire speech children must attempt to reproduce adult acoustic models using immature vocal tracts which differ from those of adults in complex ways. Control of the tongue is crucial for acceptable speech, yet the tongue is an understudied articulator because it is anatomically complex and difficult to record from using kinematic or electrophysiological methods. Nevertheless recent advances in tongue anatomy and physiology, combined with knowledge of vocal tract development, promise to shed light on the problems that children must solve in learning to speak as well as the solutions available to them. This review aims to integrate and present these findings to an audience interested in the development of speech production. A striking finding is that the tongue shows an anterior-to-posterior gradient in muscle fiber sizes and types. In multiple muscles, faster fibers are more common anteriorly while slower fibers are more predominant in the posterior tongue. Within fiber type (fast or slow) smaller fibers are seen anteriorly and larger ones posteriorly. This implies that rapid fine positioning and shaping may be particularly challenging when it involves the posterior tongue. [Work supported by NIDCD-0001247 to CReSS LLC.]