Potentiation of brain stimulation reward by weight loss: Evidence for functional heterogeneity in brain reward circuitry

Physiological need states can influence goal-directed behavior by modulating the neural circuitry underlying the rewarding effects of stimuli and behaviors. Direct electrical stimulation of this circuitry produces a powerful rewarding effect, which is called brain stimulation reward. Chronic food restriction resulting in body weight loss potentiates brain stimulation reward, but in only in a subset of cases. This could reflect individual differences between rats or subtle difference in electrode location that lead to differential excitation of functionally different components of the neural circuitry underlying brain stimulation reward. To distinguish between these views, the influence of chronic food restriction on brain stimulation reward was assessed in rats bearing multiple stimulation electrodes. In 5 of 13 cases, the rewarding effects produced by stimulating different sites in the same rat were altered differentially by weight loss. This finding is interpreted in terms of the subdivision of brain reward circuitry along functional and anatomical lines.