Dopaminergic Neuromodulation of Decision Making in Young and Middle-Aged Adults

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PROJECT SUMMARY / ABSTRACT Vital financial decisions are made during pre-retirement age that can influence financial well-being for the rest of an individual's life. However, very little psychological and neurobiological research has examined financial decision making in this pre-retirement late middle age range. An overarching goal of this grant is to begin to construct a more comprehensive model of the specific psychological and neural mechanisms that support financial decisions in young adulthood and late middle age. All aims seek to understand adult age differences in cost-benefit decisions and the specific role of dopaminergic neuromodulation in supporting these preferences in young and late middle-age adults. We particularly focus on decisions with effort costs, but we will also examine the influence of dopamine (DA) on risky choice. A single multimodal neuroimaging study will examine age and individual differences in basic cognitive and motivational variables, decision making behavior, neural reward circuits using fMRI, multiple aspects of the DA system collected across three radio- ligand PET imaging sessions, and behavioral sensitivity to the drug amphetamine. Using radioligand PET imaging of D2-like receptors and release with [18F]fallypride and DA transporters (DAT) with [18F]FECNT, the project will provide the first examination of the specific role of multiple aspects of DA function in supporting the core motivational processes underlying cost-benefit decision making in healthy young and middle-aged adults. We expect to observe differential age effects in both functional neural activity assessed with fMRI and DA function assessed with PET. Across imaging methods, we expect to observe some level of preservation of function in the ventral striatum and midbrain in late middle age. However, we expect to observe larger age differences in lateral cortical D2 receptors, striatal and ventromedial prefrontal DA release, and DAT expression. We expect these neurobiological age differences, especially in medial prefrontal and striatal networks, to be associated with decision making, such that individual differences in the function of these systems are associated with individual differences in the tolerance of effort costs. We will also include an amphetamine challenge to examine the influence of DA release on decision preferences. This will be the first study of human age differences in DA release, and the first study of DA drug effects on decision making across adulthood. The parallel use of the DAT ligand [18F]FECNT will allow us to uniquely assess the relative and possibly synergistic impact of presynaptic and postsynaptic DA variables, and to further provide a unique assessment of the relations between DAT expression and amphetamine-induced DA release and the behavioral effect of amphetamine. Beyond contributions to the study of human aging, the work will clarify the neural substrates of cost-benefit decision making across adulthood. This multimodal, adult developmental approach has the potential to more precisely characterize the neurobiological systems involved in motivation and decision making, and has the potential to identify focused targets for future interventions.