Tongue and hyoid movements in feeding and speech

Abstract

Feeding and speech depend on integrated movements of the jaws, tongue surface and tongue base–hyoid complex. Phylogenetically and ontogenetically, the movements of feeding antedate those required for speech. The hypothesis that speech movements would fall within the range used in feeding was tested.Lateral projection videofluorographic records were made for 10 subjects eating 8 g samples of three foods and reading a standard diagnostic speech text (Grandfather Passage). Radiopaque markers were glued to the upper and lower canines and tongue. Marker positions (Cartesian coordinates) for each video frame were plotted relative to the upper occlusal plane (X axis) and to a perpendicular dropped from that plane at the upper canine (Y axis). A plot of all coordinates per record gives the spatial domain (in the sagittal plane) within which a given marker moved.Tongue marker domains showed an extraordinary range of movement in feeding with extensive palatal contact. In speech, there was little palatal contact, and markers moved within a smaller sagittal domain. Although speech domains fell within the range for feeding, their centroids were highly statistically different, P < 0·001 (Hald test for differences in bivariate populations). In contrast, the hyoid domain for speech was anterior to that used in feeding and had almost no overlap with it (P < 0·0001). Our hypothesis is confirmed for the tongue surface markers but not for the hyoid. We conclude that patterns of hyoid movement in speech are a specific adaptation for speech.This research was supported by USPHS NIDCD Award 02123.