Investigation On The Neural Basis Of Human Economic Decision Making With Resting State FMRI

During my Ph.D. candidate period, I completed and joint in several studies on the neural basis and psychological mechanisms of human economic decision making. The studies focused on:(1) the association between resting state brain function and human impulsivity in economic decision making (Chapter Ⅱ and Ⅲ; using delay discounting task); (2) the neural correlates in choice process of risky decision making (Chapter Ⅳ; using risk discounting task); (3) the neural basis of learning process in ambiguous decision making (Chapter Ⅴ; using Iowa gambling task); and (4) the psychological mechanism of rejection to unfair offers in social decision making (Chapter V; using Ultimatum Game).In Chapter Ⅱ, a study using delay discounting task (DDT) was introduced. DDT is used to study a classical economic phenomenon, where an individual’s valuation of a future reward declines as the delay until reward delivery increases. DDT could measure individuals’ impulsivity in economic decision making. Increasing neuroimaging evidence suggests an association between impulsive decision-making behavior and task-related brain activity. However, the relationship between impulsivity in decision-making and resting state brain activity remains unknown. Some studies found that substances abusers, who showed high impulsivity in DDT, were altered in their resting state brain function. Thus, the present study investigates the association between the resting state functional connectivity of DDT-related brain regions and individuals’impulsivity in the task. We localized four different functional networks with DDT-related fMRI data, calculated the resting state functional connectivity intensities within and between these networks, and then entered into a multiple regression analysis with individuals’ impulsivity in DDT. The results showed that the functional connectivity intensities of the networks showed significant correlation with individuals’impulsivity, with different directions for different networks. Next, we conducted internal validation (with the original sample) and external validation (with a new recruited sample), and demonstrated that resting state brain function could predict one’s impulsivity. These reslts provided more evidence on the neural basis of impulsive decision making, and suggested a potential bio-maker to meaure one’s impulsivity. The related paper has been published in the Journal of Neurscience (Li and Ma, et al.2013; see appendix for the cover page).In Chapter Ⅲ, we analyzed the graph properties of the entire network which was formed by all the DDT-related brain regions. We found that high impulsive individuals held low global efficiency for the entire DDT-related network, while their strong functional connectivity contributed more to local efficiency. These results suggested that impulsive individual might be attenuated in the global information exchange but enchanced in the local information exchange. This could provide a new perspective on the neural basis of impulsive decision making.In Chapter IV, we investigated the neural basis of risk discounting task (RDT). RDT is a paradigm to investigate individuals’aversion to the reward which is bound with risk in economic decision making. While previous studies focused on the neural basis of reward and risk, or their interaction in the task, which could be considered as the valuation process of the task, the present study investigated the neual basis of choice process of the task. We identified the brain regions associated with choice process in RDT with a parametric fMRI design. The brain regions included frontoparietal brain regions, dorsal anterior cingulate, and anterior insula. Further, we analyzed the association between individuals’risk aversion and the task-induced activity, resting state functional connectivity of these regions. The results showed that task induced activity, and resting state functional connectivity, in several prefrontal regions were positively correlated with individuals’risk aversion, which suggested these brain regions could inhibit one’s risky decision making behavior. Our results indicated that the brain regions related to choice process in RDT may play essential roles in the task.In Chapter V, the other two projects I have joint were introduced, which respectively focused on the neural basis of learning process in ambiguous decision making, and the rejection behavior to unfair offers in social economic decision making under the anonymous situation. In the first project, we compared the brain activations of Iowa gambling task and the corresponding control task, and identified the brain regions associated with learning process in valuation and choice stage of decision making, including posterior cingulate and inferior parietal lobe, respectively. These results suggested that the learning process in ambiguous decision making might be associated with memory and attention. In the second project, with a behavior paradigm which ensured the anonymous situation, we proved that, the rejection behavior to unfair offers in social economic decision making, could still exist without external cognitive factors such as social reputation. This result provided more direct behavior evidence for the hypothesis that pure emotion could induce rejection behavior in social economic decision making. The paper of the second study has been published in the PLoS ONE (Ma, Li, et al.2012; see appendix for the cover page).With several studies and different perspective, we investigated the neural basis and psychological mechanisms of economic decision making. Our research provides more evidence for the neurobiological framework of economic decision making.