Neural Mechanisms of Central Taste Processing

Taste helps to distinguish compounds that an animal needs from those that might be toxic. The psychological property the brain attaches to taste-evoked activity that accomplishes this distinction is called hedonic tone and, absent learned effects, its behavioral manifestation is ingestion or rejection. A positive hedonic tone, i.e. palatable taste, stimulates feeding and is one of many dietary factors associated with excess energy intake and, in the long term, may lead to obesity, diabetes, and hypertension. My research focuses on how forebrain and visceral systems related to ingestive behavior control taste processing in the first and second central synapses of the ascending gustatory system. The behavioral response to taste information originating from the oral cavity is dynamic and can be modulated by experience and immediate physiological state. For example, gastrointestinal-feedback signals can switch the response from ingestion to rejection. This fundamental behavioral change characterizes hunger and satiety. If taste is to provide the information on which the decision to swallow or reject is based, its signals should be modifiable to reflect those changes. Indeed, this is the case, because coincident with behavioral changes in food acceptance is selective alterations in the responses of brain stem taste cells. Using electrophysiological, neuroanatomical, neurochemical, and lesion analysis, we investigate the underlying mechanisms of central modulation of taste processing.