The proposed research is to understand the extent of integration in the brainstem of sensory information from the posterior oral cavity and larynx. Receptors in these areas respond to thermal, chemical, and mechanical stimuli and initiate a number of upper airway protective reflexes, such as gagging, coughing, choking and swallowing. Sensory information from thse receptors travels in the glossopharyngeal and superior laryngeal nerves and projects to three areas with a known role in oral-laryngeal reflex control: the solitary nucleus, the trigeminal nucleus and an area in the pons. We propose to record neurophysiological responses from single neurons in each of these three brainstem projection areas while stimulating the epiglottis and posterior tongue with chemical, tactile and thermal stimuli. New information will be collected on the extent to which input from the two receptor areas converge onto single neurons, and on the breadth of responses of brainstem neurons to one or more stimulus modalities (taste, touch, temperature). Comparisons will be made of the response characteristics of neurons in the three brainstem areas. Experiments will be conducted in lambs since there is already a body of knowledge on the physiology of upper airway reflexes in these animals. These results will contribute to understanding how sensory information is integrated at the brainstem level to play a role in initiation and control of upper airway reflexes. Abnormalities of the triggering mechanisms of upper airway reflexes and aberrant neuromuscular patterns in the reflexes are serious clinical problems. The proposed research will provide new information related to the neural basis of these abnormalities and suggest improved methods of treatment.
