Abstract
Background: This manuscript, the sixth in a series, discusses an investigation into production of lingua-alveolar stop consonants /tE/ and /dE/ 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 (/tE/ and /dE/). 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 /tE/ and /dE/ 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 /tE/ and /dE/, and the relationships of variables during movement and predictive variable correlation values. Results: Results revealed that /tE/ and /dE/ 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 /dE/ (r=0.581, p 0.05). In vertical axis for /dE/, both DVs were significantly correlated with all IVs except mylohyoid with lower incisor (r=0.233, p>0.05). For /tE/, 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 /dE/ distinct and identifiable from /tE/.
Highlights
Congenital aglossia (CA), a rare condition in which an individual is born without a tongue [1,2], presents unique challenges when considering the anatomical and physiological demands of speech, tasting, chewing, and swallowing
In 1986, one person with CA (PwCA) was identified, and became the participant of subsequent research based on cineradiographic films (CRFs), audio/ visual recordings, videoflouroscopy, electropalatography (EPG), taste testing, and in-vivo analysis that has provided a wealth of information regarding the adaptations in vocal tract resonance characteristics, modifications to articulatory processes, alternate neurological pathways to taste discrimination, and altered patterns of chewing and swallowing
The initial research papers [4,5] provided an in-depth explanation of the disorder, background on the participant, the process of data collection, and analysis of CRFs and audio/visual recordings, as well as an exploration of listener perception and acoustics of vowels produced in isolation and in the contexts of consonant-vowel (CV) and vowel consonant (VC)
Summary
Congenital aglossia (CA), a rare condition in which an individual is born without a tongue [1,2], presents unique challenges when considering the anatomical and physiological demands of speech, tasting, chewing, and swallowing. In the second paper [5], which detailed a study of semantic/ phonemic listener confusions and consonant acoustics, it was concluded that the unusual acoustic characteristics that may have influenced the confusions in listener perceptions could be due to: (a) use of the mylohyoid/geniohyoid, which allows for partial, but insufficient constriction in the anterior oral cavity region, (b) both backing and fronting of the mandible as a means of assisting the mylohyoid/geniohyoid and tongue base in producing a point of constriction with the palate, (c) the presence of craniofacial macrosomia, retrognathia, and micrognathia, which limit the size of the oral space and the vowel space, (d) reduced articulatory movement, notably lip spreading, which inhibits the production and interpretation of front vowels and consonants, and (e) co-articulatory limitations, present in CV and VC production, that require close constrictions or wide serial movements. It should be noted that in the CV and VC syllables, stimuli consisted of both real words and nonsense syllables, with no significant or descriptive statistical difference in listener perception between the real words and nonsense syllables [3,4]
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