ANATOMIC DEVELOPMENT OF THE VOCAL TRACT--MRI PROCEDURES

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The vocal tract structures subserve the functions of speech communication and food ingestion throughout the lifespan. Especially during the periods of infancy, early childhood, and adolescence, these structures undergo changes in size, shape, and relative configuration that affect their participation in oral motor functions. Although the evidence for anatomic remodeling is compelling, knowledge of the details of the process is remarkably limited. This research has two primary goals: (1) to study the anatomic development of the vocal tract structures in children with normal vocal tract growth; and (2) to compare the findings from children with normal growth to data from children with documented speech disorders partially attributable to characteristic structural differences secondary to chromosomal aberration, namely Trisomy 21. These goals will be achieved through the use of Magnetic Resonance Imaging (MRI), which is suited for the study of both soft and hard tissues that comprise the vocal tract. The procedure entails the selection of suitable MR images, digitizing these images, and utilizing image measurement software to obtain data for 36 predefined measures of the head and neck regions. The measurement set proposed is more extensive than that in any published data source and therefore promises a substantial increase in information on vocal tract growth and development. Preliminary results from children between the ages of birth to 4 years support inferences from the literature that some structures have synchronous growth and that such coordinated growth is evident during periods of accelerated growth (growth spurts). Specific issues to examine include: a) the relative rates of growth of the hard and soft tissues; b) the coordinated growth of the different structures; i.e. synchrony in growth (both hard and soft tissues); c) growth spurts, and synchrony in growth spurts; d) the ideal index to document and predict the growth of the vocal tract structures; e) gender related differences in the growth of the vocal tract structures; f) comparison of growth patterns pre versus post adolescence; g) anatomic growth similarities and differences in normal children and children with Trisomy 21. The normal aspect focus of this project includes subjects between the ages 4 and 18 (age of maturity); the disordered aspect focus includes subjects with Down's syndrome (DS) between the ages birth to 21. The findings of this study contribute to knowledge on craniofacial development, and are of theoretical and clinical significance particularly in the areas of speech development and speech production.