Frontoparietal dynamics and value accumulation in intertemporal choice

Abstract

Intertemporal choice requires choosing between a smaller reward available after a shorter time delay and a larger reward available after a longer time delay. Previous studies suggest that intertemporal preferences are formed by generating a subjective value of the monetary rewards that depends on reward amount and the associated time delay. Neuroimaging results indicate that this subjective value is tracked by ventral medial prefrontal cortex (vmPFC) and ventral striatum. Subsequently, an accumulation process, subserved by a network including dorsal medial frontal cortex (dmFC), dorsal lateral prefrontal cortex (dlPFC) and posterior parietal cortex (pPC), selects a choice based on the subjective values. The mechanisms of how value accumulation interacts with subjective valuation to make a choice, and how brain regions communicate during decision making are undetermined. We developed and performed an EEG experiment that parametrically manipulated the probability of preferring delayed larger rewards. A computational model equipped with time and reward information transformation, selective attention, and stochastic value accumulation mechanisms was constructed and fit to choice and response time data using a hierarchical Bayesian approach. Phase-based functional connectivity between putative dmFC and pPC was found to be associated with stimulus processing and to resemble the reconstructed accumulation dynamics from the best performing computational model across experimental conditions. By combining computational modeling and phase-based functional connectivity, our results suggest an association between value accumulation, choice competition, and frontoparietal connectivity in intertemporal choice. Author summaryIntertemporal choice is a prominent experimental assay for impulsivity. Behavior in the task involves several cognitive functions including valuation, action selection and self-control. It is unknown how these different functions are temporally implemented during the course of decision making. In the current study, we combined formal computational models of intertemporal choice with a phase-based EEG measure of activity across brain regions to show that functional connectivity between dmFC and pPC reflects cognitive mechanisms of both visual stimulus processing and choice value accumulation. The result supports the notion that dynamic interaction between frontopatietal regions instantiates the critical value accumulation process in intertemporal choice.