The object of the proposed research is to determine: the mechanisms involved in the change of tongue shape of cats and macaques (as an analogue for man) during normal feeding and swallowing; the influence of the mechanical properties of food within the oral cavity on tongue shape during the transport and manipulation of food (ingestion to swallow); and the effect of intra-oral stimuli on a stereotyped output of central nervous system pattern generators governing the synchronized activities of food breakdown and transport. This information is currently not available and as this investigation will establish the parameters of tongue function in feeding, it will provide a basis for understanding feeding disorders in cerebrally impaired children, problems of growth and development, tongue and soft palate movements during speech and provide additional information on the neuronal control of the jaw/tongue complex. Macaque and cat tongues wll be sectioned to determine the internal architecture, size and distribution of the motor neuron pool and muscle fiber types. Synchronous cinefluorographic studies (with suitable metallic markers and barium) and electromyographic studies will determine changes in tongue shape during feeding of foods of different consistencies, and swallowing. Muscle activity patterns and tongue structure will be used to explain how tongue shape changes are achieved. Drugs and brainstem stimulation of decerebrated cats will be used to illicite rhythmic jaw and tongue movements. A series of artificial stimuli, designed to stimulate the effect of food, will be administered to the oral region and the changes in the output of the V, VII, IX, and XII cranial nerves will be determined. This will test the concept that all aspects of rhythmic feeding in mammals are controlled by a C.N.S. pattern generator, the output of which is modified by feedback from the oral region.