SIGNALS TO FEED: BIOLOGICAL AND ASSOCIATIVE MECHANISMS

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Models of regulatory feeding behavior often assume that animals (including humans) eat, and engage in behaviors that are instrumental to obtaining food, in response to interoceptive signals that are correlated with their level of energy need. Accordingly, much research has been devoted to specifying the metabolic and hormonal events that give rise to these types of signals and to specifying the neural substrates involved with their detection and transmission. This work has identified a variety of physiological and pharmacological manipulations that promote or suppress food intake. However, it has been difficult to separate the potential "hunger" or "satiety" signal properties of these manipulations from their possible effects on palatability, learning, nonspecific behavioral arousal or other mechanisms that are also known to influence feeding even in the absence of changes in energy need. Integrating methods and concepts from psychobiology and Pavlovian conditioning, the proposed research will develop and exploit a novel model of regulatory feeding behavior that describes how interoceptive signals of energy need act in conjunction with food cues (e.g., tastes and other sensory properties of food) and the postingestive consequences of intake to determine the strength or probability of appetitive and consummatory feeding behavior. Based on studies of Pavlovian conditioned modulation involving conventional auditory and visual stimuli, this model assumes that energy state signals influence feeding behavior by modulating the capacity of food-related stimuli to activate the memory of the appetitive postingestive consequences of intake. New research strategies are proposed to examine the involvement of metabolic, hormonal, subdiaphragmatic vagal, and central nervous system mechanisms in this "memory modulation" process. In addition, several experiments will assess the nature of the information that animals encode about the foods that they eat as well as the nature of the signals involved with the retrieval/activation of that information. It seems likely that disordered patterns of human feeding behavior involve impairments in the detection, utilization, or modulatory function of energy state signals or in the encoding of information about food. Thus, the proposed research may have important implications with respect to understanding the etiology and developing effective treatments for these disorders.