Bilabial Substitution Patterns During Consonant Production in a Case of Congenital Aglossia

Abstract

Purpose: Congenital aglossia is a rare syndrome in which an individual is born without a tongue. The present paper examines articulatory details of the production of multiple consonants by an aglossic speaker. Method: Real-time magnetic resonance imaging data of the upper airway were collected from the aglossic speaker. Air-tissue boundaries were determined from the video sequences using a segmentation algorithm, and dynamics of vocal-tract constrictions and cross-dimensions were calculated. Results: The aglossic speaker produced the consonants /t, d, th, l ,r, f ,v, s, sh/ with a bilabial closure instead of a normal lingua-alveolar closure; however, in /t/and /d/ the overall vocal-tract configuration presented a cavity anterior to the constriction, which filtered transient and frication sources in a manner similar to normal alveolar production. Conclusion: The aglossic speaker, lacking a tongue apex, has developed a bilabial compensatory strategy to produce multiple consonants with her lips.