Indexing tongue profile narrowing for English lateral consonants using 3D volumetric MR imaging

Abstract

Production of lateral consonants in many languages involves separate but coordinated tongue tip and tongue rear actions—raising of the tongue tip and retraction of the tongue body. Given these gestures and the presence of lateral airflow, it has been speculated that horizontal (i.e., side-to-side) narrowing of the tongue may occur during production of these laterals, either as a passive result of the anterior-posterior lingual stretching or as an actively controlled movement. This study uses 3D volumetric MR scans of speakers producing a variety of sustained English sounds to examine horizontal tongue width as a function of consonant laterality/centrality and as a function of vowel height in front vowel contexts. Multiplanar reconstruction of volumetric data for each token and subject permitted imaging of the static postures on the axial plane. We determine a protocol for identifying a specific oblique axial slice in terms of mid-sagittal anatomical landmarks that allows for a stable and informative index of horizontal tongue width. This index demonstrates utility for identifying and quantifying tongue profile narrowing specific to English lateral consonants. [Work supported by NIH.]