Poster D103, Monday, March 26, 8:00-10:00 am, Exhibit Hall C
Individual differences in dopamine D2 receptors and neural representations of subjective reward value
Jaime Castrellon1, Linh Dang2, Jacob Young3, David Zald2, Gregory Samanez-Larkin1; 1Duke University, 2Vanderbilt University, 3University of California, San Francisco
Previous pharmacological and genetic studies have implicated the dopamine system in intertemporal decision making. However, there is almost no evidence for an association between direct measures of dopamine function and discounting in humans. Here, we directly examined how individual differences in dopamine receptors related to individual differences in neural representations of subjective reward value in healthy humans. Seventeen young adults completed a delay discounting task during a functional MRI (fMRI) scan. During the task, subjects made 96 choices between smaller-sooner and larger-later rewards. On a separate visit, participants completed a PET scan with the high-affinity D2-like receptor tracer [18F]fallypride to identify regional binding potential (BPND). For each subject, choice data were fit with a hyperbolic discounted value function and softmax decision function. Estimated time discount rates (k) were used to calculate the subjective value of the chosen and unchosen options for each trial. FMRI data processing was carried out using FEAT in FSL using standard preprocessing. Following autocorrelation correction, each subject’s data was fit with parametric convolved regressors representing the subjective value of the chosen and unchosen options. In a whole brain analysis, BPND from an a priori region of interest in the midbrain (an index of autoreceptor availability) was negatively correlated with BOLD signal associated with the subjective value of the chosen option in the thalamus, putamen, and middle frontal gyrus (cluster-corrected at z>2.3, p<0.05). This suggests that lower autoreceptor binding, and presumably higher levels of dopamine release, are associated with stronger representation of subjective value during intertemporal choice.
Topic Area: THINKING: Decision making