Vocal tract length development: MRI procedures

Abstract

From infancy to adulthood, vocal tract length increases by about twofold. The purpose of this study is to assess the developmental changes in the various hard and soft tissue structures in the vicinity of the vocal tract that contribute toward its length. Magnetic resonance images (MRI) from children (birth to 6 years) and adults were used since MRI provides detailed visualization of the soft tissues in the oral and pharyngeal regions along with adequate visualizations of related bony and cartilaginous structures. Using previously established measurement procedures (Vorperian et al., 1999), the following structures were measured: lip thickness, hard and soft palate length, tongue length, oro- and naso-pharyngeal length, mandibular length, and position of the hyoid bone and larynx in relation to the nasal spine. Findings will be discussed in terms of: (a) the relative contribution of the various structures toward vocal tract length and how the extent of contribution changes with age; and (b) the relative and relational growth of the different structures. Findings provide normative data on the various vocal tract structures measured; also, they contribute toward understanding the anatomic changes that may be a substrate to speech emergence and development. [Work supported by NIDCD Grant No. R03-DC 4362.]