The sense of taste enables an organism to identify potential sources of food. Whether the organism ingests the food depends on its palatability as well as the homeostatic state of the animal. Gustatory processing involvesthe primary gustatorycortex (GC), the orbitofrontalcortex (OFC),the amygdala(AM) and the hypothalamus (HT). These interconnected brain areas are involved in processing a tastants' identity and its reward value as it pertains to the animal's motivation to eat We have developed the technology to simultaneously record the activity of neuronal ensemble in all four of these areas fromrats with chronically implanted electrodes that tick to obtain rewarding tastants and whose motivation, as it pertains to their state of hunger or satiety, can be modulated by eating or by peptides that will enhance or suppress their appetite. At present there is a paucity of information regarding how the interactions in and between brain areas of the taste-rewardcircuitry change as an animal eats to satiety or is made hungry or sated by the injection of appetite-modulating peptides. Our goal is to elucidate how the processing of tastants is distributed among these areas when an animal freely licks to receive tastants and when its motivation to eat changes.
Our first aim i s to test the hypothesis that the neural activity obtained from populations of GC and OFC neurons can be used to: discriminate among tastants in a single lick, anticipate the tastant that will be delivered when it is expected, and predict when an animalwill begin and terminate drinking.
The second aim i s to show how changes in motivation, as it relates to hunger and satiety, affect the processing of gustatory information throughout the taste-reward circuitry. This information will be obtained by simultaneously measuring the changes in neural activity that occur in and between the GC, OFC, AM and HT as an animal voluntarily begins feeding various tastants to satiety, and by manipulating its state of hunger or satiety through the central administration of appetite- suppressing (leptin, cholecystokinin), or appetite enhancing (neuropeptide Y, orexin, ghrelin) peptides. We will test the hypothesis that eating to satiety as well as the injection of these peptides will cause distinct changes in neural activity that will be observed throughout the circuitry and that information on the physiological state of the animal (i.e.hunger, satiation) can be more accurately obtained if neuronal information from the above mentioned brain areas are acquired simultaneously. Obtaining such knowledge is relevant to the important societal problem of obesity, which has reached epidemic proportions. In summary, we will use a novel preparation that takes advantage of state-of-the-art technology to address fundamental scientific and public health issues regarding how behaving animals process austatorv information across different motivational states. ^___
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