This proposal represents a synthesis of research concerned with the neural mechanisms that underlie the sensory control of feeding behavior. In large part, the short term control of ingestive behavior is governed by sensory neural processes originating in the oral cavity and viscera. Gustatory stimuli offer a unique sensory probe of this system, because easily specifiable chemical stimuli reliably elicit ingestion or rejection. Visceral afferent stimuli can modulate gustatory activity within the brain such that the behavioral response to the same chemical stimulus is switched from ingestion to rejection, or vice versa. This proposal focuses on two areas, the caudal brainstem and the thalamo-cortical axis. The caudal brainstem, the medulla, pons, and midbrain, contains the first central synapses for both gustatory and vagal visceral afferent axons, the motoneurons responsible for ingestive behavior, and sufficient integrative compacity to support rudimentary hunger and satiety. In the forebrain, the sensory control of ingestion is equally well documented, but the neural mechanisms involved are poorly understood. The anatomy of the gustatory system has been established, but the neural procesisng of taste information in the forebrain remains obscure. For the visceral afferent system, not even the central organizaation can be specified. Using neuroanatomical, electrophysiological, and behavioral analysis, specific experiments will examine (1) the function of oral sensory activity in eliciting and guiding ingestion and rejection behavior, (2) the nature of the visceral events that control these response, and (3) the organization, coding, and integration of the gustatory and visceral afferent activity involved in switching from one behavior to the other. These experiments will provide an opportunity to learn or develop numerous techniques, including fluorescence microscopy, chronic extracellular electrophysiology, innovative procedures for surgery and behavioral analysis, as well as to continue and expand collaborative arrangements wiht productive scientists elsewhere. In addition to contributing toward a basic understanding of how the nervous system coordinates sensory information into precise physiological behavioral controls, this research has direct relevance to the etiology of specific behavioral pathology, such as dietary obesity, bulemia, and anorexia nervosa.
