MRI studies of vocal tract development: Relative growth patterns

By H.K. Vorperian and R.D. Kent

The variability of acoustic and physiologic measures of speech production in young children is typically believed to reflect the maturation of the motor control system in that variability decreases as age increases. However, concurrent with neural maturation, the anatomy of the speech production system develops markedly during the first few years of life. This paper presents quantitative data on the anatomic changes that the vocal tract structures undergo during the first ten years of life. Magnetic resonance images (MRI) from children (birth to 10 years) were used because MRI provides detailed visualization of the soft tissues in the oral and pharyngeal regions along with adequate visualizations of related bony and cartilaginous structures. Previously established measurement procedures (Vorperian et al., 1999) were used to determine: Mandibular length, depth and width; maxillary length and width; tongue length and volume; lips’ length, thickness and area; level of larynx , epiglottis and hyoid bone; and pharyngeal length. The results show changes in the relative size of all structures and the coordinated growth of some but not all structures. Implications for clinical and theoretical issues in speech motor control are discussed.