Articulatory Movement during Production of Lingua-Alveolar Stop Consonants in a Case of Congenital Aglossia

Background: This manuscript, the sixth in a series, discusses an investigation into production of lingua-alveolar stop consonants /tʌ/ and /dʌ/ by a person with congenital aglossia (PwCA), and the specific anatomical and physiological properties and kinematics involved. Methods: In this study, a modified barium swallow study was performed to analyze the PwCA's oral and pharyngeal tract, in addition to a video speech recording made during a series of imitative tasks isolating specific English phonemes (/tʌ/ and /dʌ/). Researchers evaluated the PwCA's vertical and horizontal range of motion (ROM) of the mobile articulators (i.e., mylohyoid, tongue base, lower incisors, hyoid) during /tʌ/ and /dʌ/ production, and whether these phonemes could be predicted by their ROM and graphic representation. Additionally, researchers analyzed horizontal and vertical movement to identify correlational patterns between dependent (DVs) (i.e., lower incisors, hyoid) and independent variables (IVs) (i.e., lower lip, mylohyoid, tongue base) during production of /tʌ/ and /dʌ/, and the relationships of variables during movement and predictive variable correlation values. Results: Results revealed that /tʌ/ and /dʌ/ were distinct in specific horizontal and vertical distances of ROM and corresponding horizontal and vertical relationships. Additionally, although the horizontal correlation patterns for IVs and DVs were similar in statistical significance, this was not found between hyoid and mylohyoid. Significant positive correlations were found for /dʌ/ (r=0.581, p<0.05), but not /tʌ/ (r=295, p>0.05). In vertical axis for /dʌ/, both DVs were significantly correlated with all IVs except mylohyoid with lower incisor (r=0.233, p>0.05). For /tʌ/, only three correlations were significant. Hyoid was significantly correlated with tongue base (r=0.648, p<0.05), and lower incisors were significantly correlated with mylohyoid (r=0.420, p<0.05), and lower lip (r=0.923, p<0.05). Finally, multiple distinct ROM differences and significant correlations were observed that made kinematics of /dʌ/ distinct and identifiable from /tʌ/.