Aging and dopamine modulation of complementary control processes

Dopamine (DA) modulation of control dilemmas is subjected to moderations by various factors influencing its functional efficacy and by task demands. Highlighted findings from the first funding period reveal that effects of pharmacologically elevated tonic DA levels on goal-directed and habitual decision-making in younger adults were moderated by individual differences in DA turnover rate and weight status. Aging is one further pertinent factor that pervasively affects the integrity of the DA system by affecting DA synthesis and receptor mechanisms. Since aging populations are increasing rapidly worldwide, it is imperative to gain better understandings of how deficient DA modulation may constrain older individuals’ prioritization of complementary cognitive control processes. Existing theories and empirical findings bring to light a link between deficient DA modulation and greater random processing fluctuations (noise) in older adults. Processing noise is one of the meta-parameters of control dilemmas in the CRC’s conceptual framework. Thus, extending work from the 1st funding period, the overarching aim of this follow-up project is to investigate theoretically motivated relations between DA modulation of neuronal gain, processing fluctuations and goal-directed vs. habitual control in three functional domains that implicate the frontal-striatal and hippocampal-striatal circuitries. By administering levodopa (L-DOPA) we will conduct pharmaco-fMRI and behavioral studies in younger and older adults to investigate how aging may moderate the effects of elevated tonic DA levels on prioritizing complementary control processes during perceptual, spatial, and complex state-dependent decision-making tasks. Within the CRC, this project bridges direct experimental links to two other projects (B7 and B9) by employing the same task paradigms. At the conceptual level, this project complements other projects focusing on individual differences (e.g., B6), clinical pathology (e.g., C3), stress regulation (B5) and other neurobiological modulators (B8) of control dilemmas. Furthermore, the empirical data to be generated in this project could potentially be utilized for the purposes of further model developments by computationally oriented projects (e.g., A8, A9).

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