Biomechanical Mechanisms of Tongue Movement During Mastication

Mastication, or mammalian chewing, is the cyclic breakdown of the food bolus between the molars. Effective chewing consists of tight coordination of lips, cheeks, jaw, and tongue modulated via sensorimotor integration of tongue movement and sensation. Compromised chewing leads to risks, including digestive issues, malnutrition, and potential impacts on mental well-being and cognitive function. However, the biomechanical mechanisms driving tongue movement during mastication, remains poorly understood. In this study, we evaluated the contributing muscles toward tongue movements during mastication using biplanar videoradiography following the XROMM workflow. Using CT scans to visualize the hyolingual anatomy of opossums, we discovered that the tongue exhibits complex movements, including flexion and rolling, which are essential for effective food manipulation and bolus formation. In vivo observation of quantified marker movement reveal that the genioglossus, hyoglossus, and styloglossus muscles play crucial roles in tongue retraction and depression, while the superior and inferior longitudinal muscles facilitate fine-tuned shaping and elevation of the tongue during chewing cycles. Our findings may facilitate new treatment exercises during rehabilitation for patients with neuromuscular disorders affecting oral motor function.