Role of Fronto-Parietal Cortex in Delay Discounting

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Choices made between outcomes available at different points in the future(intertemporal choices) constitute an important and common set of decisionsencountered in everyday life. How people respond to such choices is also knownto be predictive of a number of important life outcomes, and can be summarizedusing laboratory measures of delay discounting. Understanding the cognitivebrain processes that underlie delay discounting, and particularly our ability toresist immediate temptations, is an important area of research in cognitiveneuroscience. Significant progress has been made in this area over the pastdecade. It is now well established that brain reward areas, including theventromedial prefrontal cortex (vmPFC), encode the subjective value ofprospective rewards. It is also established that a network of regions in lateralprefrontal (lPFC), dorsomedial frontal (dmFC), and posterior parietal cortex (pPC)are engaged when making intertemporal choices. However, the role of thisfronto-parietal cortical network (FPN) remains debated and less understood. Thecurrent research project builds on recent computational modeling work done byMcClure and his colleagues to test and unify competing theories of FPN functionin delay discounting. This work promises to further our understanding of the brainbasis of important cognitive processes related to the exertion of willpower andself-control.We will conduct three studies that employ both fMRI and EEG to investigate therole of different frontal and parietal regions in intertemporal decision-making. Inpreliminary work, we have used our computation model framework todemonstrate that (1) the pPC interacts with the vmPFC during the valuing ofchoice options, and (2) value information is accumulated in the dmFC duringaction selection. This project will further test how the FPN functions underconditions of temptation and cognitive load and how these manipulationsinfluence choice outcomes. A number of disorders, including attention deficithyperactivity disorder and drug addiction, have been directly associated withdelay discounting. The proposed studies of delay discounting therefore representa clear example in which cognitive neuroscience approaches promise to directlyimpact and improve our understanding of normal and aberrant behavior. Finally,decision neuroscience is a highly interdisciplinary field that combines elements ofeconomics, psychology, and neuroscience. It offers an exciting trainingopportunity for the students at various levels of training who will be directlyinvolved in the project.