MRI & CT Studies of the Developing Vocal Tract

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DESCRIPTION (provided by applicant): The oral and pharyngeal cavities making up the vocal tract undergo changes in size, shape, and relative proportions during the growth process from infancy through early childhood and adolescence. While acoustic theory indicates that vocal geometry is predictive of the spectrum shape of speech sounds, the relation between developmental changes in the vocal tract to changes in speech acoustics has not been adequately investigated. This is due to the scarcity of quantitative information on the anatomic remodeling of the vocal tract during development. To address this, we devised a magnetic resonance imaging (MRI) procedure to measure 36 predefined structures of the head and neck (Vorperian, et al., 1999) and secured an imaging database of 300 typically and 10 atypically (Trisomy 21) developing cases. This enabled us to construct a unique database of measurements on the concurrent development of the head, face and vocal tract structures. Our novel findings indicate that the development of vocal tract length follows a growth curve that is intermediate to the neural and somatic growth curves; that the relative contribution of the different vocal tract structures towards its lengthening changes during the course of development; and that the synchronous growth in hard and soft tissue structures persists during periods of accelerated growth. The proposed project combines imaging, acoustic analysis, and geometric modeling in an investigation of the development of the vocal tract from infancy through adulthood. The goals of this proposed research are to: (1) expand our measurement database by making additional linear and volumetric measurements, and supplement it with acoustic measurements representative of the specified vocal tract anatomy; (2) statistically model general trends in the individual and synchronous growth patterns of the vocal tract structures; (3) configure geometric models of the developing vocal tract and compute formant frequencies; and (4) correlate computed formant values with age specific acoustic data to make inferences regarding developmental patterns of articulator mobility. These goals will be addressed through our MR imaging database that spans the entire developmental period of typically and atypically developing cases, and a similar computerized tomography (CT) image database that will be secured. The findings will be of theoretical and clinical significance for an improved understanding of the anatomic correlates of speech development.