The proposed research will investigate the functional and anatomical organization of the gustatory system in the forebrain of nonhuman primates. This research represents a logical extension of the primate neurophysiological and neuroanatomical experiments that have been underway for several years in this laboratory. Our initial anatomical experiments defined the central gustatory and visceral pathways in Old World monkeys and laid the framework for our subsequent neurophysiological research. This research has provided important, fundamental information about the coding of gustatory information in the thalamus and raised other questions about the connectivity of thalamic gustatory neurons with cortex. The areas of the forebrain that will be investigated include the thalamic taste area (VPMpc), insular (Ins) and opercular (Opc) cortices, and a discrete part cortical area 3b subjacent to the anterior subcentral sulcus (pre-3b). These three areas of cortex receive projections from neurons in the thalamic taste area (VPMpc), however, the role that each plays in gustatory perception is unknown. The proposed research will use electrophysiological and neuroanatomical techniques to describe the functional and synaptic organization of the gustatory system at the thalamic and cortical levels. Intraoral fluid stimuli will be used to: 1) determine the degree of gustatory, tactile, and thermal specificity of individual neurons in each area; and 2) define the differential sensitivity of single neurons to various sapid stimuli. Modern neuroanatomical tracing techniques will he used to describe the density and distribution of neurons in the gustatory thalamus and other subcortical areas that project to individual or multiple cortical gustatory areas. Antidromic stimulation techniques will be used to determine the cortical connectivity of individual, physiologically identified, thalamic gustatory and intraoral, somatosensory neurons. These neurophysiological experiments in awake monkeys will contribute important information about the functional organization of gustatory cortex and may be relevant to certain pathological types of ingestive behavior (e.g. anorexia nervosa and bulimia) that require cortical involvement.
