The tongue is essential in normal oromotor function, and is of pre-eminent importance in the production of human speech. Tongue dysfunction is associated with many human clinical syndromes. Yet the design of effective treatments for recovery from tongue dysfunction is hindered by our limited understanding of the neuromuscular bases for tongue motor control. Most critically, we lack information on the organization of the fundamental output elements of the tongue motor system, i.e., tongue muscles, tongue muscle compartments and tongue motor units. The long term goals of this study are to determine the neuromuscular organization of these functional output elements in the human tongue motor system and to improve clinical treatments for recovery from tongue dysfunction. To achieve these goals this study applies anatomical and physiological techniques directly to investigations of the human and non-human primate tongue. The results of these investigations will meet three general aims. First, the architecture of human tongue muscles and the pattern of their motor innervation will be studied to determine the neuroanatomical bases of muscle biomechanical diversity in the human tongue. Second, the identity and distribution of muscle fiber types in the human tongue will be determined to test the hypothesis of parallel anatomical systems for human tongue movement. Third, the morphology and physiology of tongue motor units and muscle compartments will be determined in the non-human primate to allow physiological correlation of anatomical organization. These studies will provide the first detailed understanding of the functional output elements of the human and non-human primate tongue. This understanding is essential if we are to develop accurate models of tongue motor control and if we are to design rational interventions for recovery of tongue function in human disease
