Laryngeal movements including breathing, phonation, and airway protective reflexes, such as swallowing and coughing, are mainly controlled by the neuronal networks in the brain stem. To understand the mechanisms underlying these movements, the morphological and functional properties of the brain stem neurons that participate in the production of these movements should be investigated. We previously examined the functional roles of the brain stem neurons that contribute to the generation of laryngeal movements using electrophysiological and morphological procedures. The findings of two studies are introduced in the presentation. In the first study, we reported the projections of the swallow-related neurons in the swallowing central pattern generator in the medulla oblongata using a tracer injection in anesthetized paralyzed guinea pigs. This study indicated that the swallowrelated neurons were broadly distributed in the nucleus tractus solitarius and reticular formation, and that there appeared to be complex interconnections amongst the nucleus tractus solitarius, the reticular formation, and the cranial motor nuclei. The other study showed that the activity of the respiratory neurons in the ventrolateral medulla, in particular between the Bötzinger complex and the rostral ventral respiratory group, was altered during fictive vocalization, swallowing, and coughing in a type-specific manner, and thus supported the hypothesis that the medullary respiratory neurons are multifunctional and that the respiratory center in the network circuitry underlying these behaviors can be shared.
