Meeting Abstract
The tongue plays a crucial role in feeding, but is notoriously difficult to study. Most attempts to quantify the tongue’s contribution to chewing and swallowing have been limited to single-plane X-ray video, and thus fail to capture its dynamic shape changes in three dimensions. Here, we use XROMM to measure and quantify 3D tongue shape dynamics during feeding. Two Rhesus macaques (Macaca mulatta, both male), were surgically implanted with 24 tantalum markers in the cranium (4), mandible (4), hyoid (1), and tongue (15). Biplanar videoradiographic data were collected while the monkeys fed on grapes, gummy bears, and almonds. Using a new machine learning workflow, at least 1000 gape cycles per individual were tracked, and the motion of the mandible, hyoid, and tongue markers relative to the cranium was reconstructed. A Procrustes superimposition was performed on the tongue marker positions to isolate shape. We then performed a principal component analysis on the transformed data and found that 80% of the variance in the data was explained by the first six principal components. After scaling to percent of gape cycle duration, we compared tongue shape within and across gape cycle types and feeding sequences. As predicted, tongue shape differed significantly between chews and swallows. Notably, these differences emerged as early as the first 10% of the cycle, during the fast-close phase. Finally, the mean variation in tongue shape decreased consistently over the duration of a feeding sequence, reaching a minimum at the terminal swallow. These geometric morphometric analyses reveal global changes in tongue shape independent of tongue or jaw position; our future analyses will quantify the impact of these factors on tongue shape.
