The Neural Mechanisms of Intertemporal and Risky Choice

Abstract

This dissertation aims to investigate the neural mechanisms of intertemporal and risky economic choices and the relationships between choice preferences and impulsivity. Previous research has revealed a role for the Dorsolateral Prefrontal Cortex (DLPFC) in both risky and intertemporal choices and has revealed a role for the Posterior Parietal Cortex (PPC) in intertemporal choices. However, many questions regarding the functions of these regions during choice remain unanswered. In order to better understand the role of these regions, repetitive Transcranial Magnetic Stimulation was used to disrupt functioning in the DLPFC or PPC before individuals completed monetary choice tasks. In Experiment 1, it was found that disruption of either the right DLPFC or right PPC led to increased choice of better immediate but worse long-term options on an intertemporal choice task; these results were observed both for choices involving gains and choices involving losses. While disruption of the DLPFC led to a general shift in preference, the effects of disrupting the PPC depended on the relative value of the two options. In Experiment 2, disruption of either side of the DLPFC led to increased choice of riskier options with larger possible gains on a task without losses; this effect was dependent upon the probability level of obtaining the gain. The pattern of results across the two experiments suggests that during choice, the DLPFC is involved in valuation of options and ascribes different values to options than do other brain regions, whereas the PPC is involved in cognitive control. Experiment 3 investigated the association of individual differences in choice preferences for delayed and risky incentives with individual differences in impulsivity. No strong relationships were observed, indicating that impulsivity as measured on self-report scales has little relationship with behavior on choice tasks. Understanding the neural mechanisms of economic choices will not only elucidate how consumers make economic decisions, but will also help reveal the mechanisms by which humans and other animals make choices more broadly.