Abstract
The process by which the value of delayed rewards is discounted varies from person to person. It has been suggested that these individual differences in subjective valuation of delayed rewards are supported by mesolimbic dopamine D2-like receptors (D2Rs) in the ventral striatum. However, no study to date has documented an association between direct measures of dopamine receptors and neural representations of subjective value in humans. Here, we examined whether individual differences in D2R availability were related to neural subjective value signals during decision making. Human participants completed a monetary delay discounting task during an fMRI scan and on a separate visit completed a PET scan with the high affinity D2R tracer [18F]fallypride. Region-of-interest analyses revealed that D2R availability in the ventral striatum was positively correlated with subjective value-related activity in the ventromedial prefrontal cortex and midbrain but not with choice behavior. Whole-brain analyses revealed a positive correlation between ventral striatum D2R availability and subjective value-related activity in the left inferior frontal gyrus. These findings are the first to identify a link between directly-measured mesolimbic dopamine function and subjective value representation in humans and suggest a mechanism by which individuals vary in neural representation of discounted subjective value.
Footnotes
Author Note: Some of the results reported in this manuscript were presented in a poster at the annual meeting of the Cognitive Neuroscience Society (2018) and the Society for Neuroeconomics (2018). Correspondence concerning this article should be addressed to Jaime Castrellon, Center for Cognitive Neuroscience, Duke University, Box 90999, Durham, NC 27708. Email: jaime.castrellon{at}duke.edu
Data Availability: Raw fMRI and PET data used in the manuscript can be viewed and downloaded from OpenNeuro (https://openneuro.org/datasets/ds002041). Unthresholded voxelwise statistical fMRI maps can be viewed and downloaded on NeuroVault (https://neurovault.org/collections/PDSRXDAH/). Data and code used in analyses can be viewed and downloaded on OSF (https://osf.io/6p4rk/).
