Individual differences in dopamine D2 receptor availability correlate with reward valuation.

Reward valuation, which underlies all value-based decision-making, has been associated with dopamine function in many studies of nonhuman animals, but there is relatively less direct evidence for an association in humans. Here, we measured dopamine D2 receptor (DRD2) availability in vivo in humans to examine relations between individual differences in dopamine receptor availability and neural activity associated with a measure of reward valuation, expected value (i.e., the product of reward magnitude and the probability of obtaining the reward). Fourteen healthy adult subjects underwent PET with [18F]fallypride, a radiotracer with strong affinity for DRD2, and fMRI (on a separate day) while performing a reward valuation task. [18F]fallypride binding potential, reflecting DRD2 availability, in the midbrain correlated positively with neural activity associated with expected value, specifically in the left ventral striatum/caudate. The present results provide in vivo evidence from humans showing midbrain dopamine characteristics are associated with reward valuation.