Proceedings of the National Academy of Sciences of the United States of America
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Proc. Natl. Acad. Sci. U.S.A. · Jul 2011
Disentangling pleasure from incentive salience and learning signals in brain reward circuitry.
Multiple signals for reward-hedonic impact, motivation, and learned associative prediction-are funneled through brain mesocorticolimbic circuits involving the nucleus accumbens and ventral pallidum. Here, we show how the hedonic "liking" and motivation "wanting" signals for a sweet reward are distinctly modulated and tracked in this circuit separately from signals for Pavlovian predictions (learning). Animals first learned to associate a fixed sequence of Pavlovian cues with sucrose reward. ⋯ Microinjection of a dopamine-stimulating drug instead enhanced only the motivation component but did not alter hedonic impact or learned prediction signals. Different dedicated neuronal subpopulations in the ventral pallidum tracked signal enhancements for hedonic impact vs. incentive salience, and a faster firing pattern also distinguished incentive signals from slower hedonic signals, even for a third overlapping population. These results reveal separate neural representations of wanting, liking, and prediction components of the same reward within the nucleus accumbens to ventral pallidum segment of mesocorticolimbic circuitry.