The role of ventromedial prefrontal cortex in reward valuation and future thinking during intertemporal choice.

Elisa Ciaramelli,Donna Kwan,Carl Craver,Francesca Bianconi,Leonard Green,Joel Myerson,Violetta Knyagnytska,Jenkin Mok,R Shayna Rosenbaum,Flavia De Luca

doi:10.7554/elife.67387

Abstract

Intertemporal choices require trade-offs between short-term and long-term outcomes. Ventromedial prefrontal cortex (vmPFC) damage causes steep discounting of future rewards (delay discounting [DD]) and impoverished episodic future thinking (EFT). The role of vmPFC in reward valuation, EFT, and their interaction during intertemporal choice is still unclear. Here, 12 patients with lesions to vmPFC and 41 healthy controls chose between smaller-immediate and larger-delayed hypothetical monetary rewards while we manipulated reward magnitude and the availability of EFT cues. In the EFT condition, participants imagined personal events to occur at the delays associated with the larger-delayed rewards. We found that DD was steeper in vmPFC patients compared to controls, and not modulated by reward magnitude. However, EFT cues downregulated DD in vmPFC patients as well as controls. These findings indicate that vmPFC integrity is critical for the valuation of (future) rewards, but not to instill EFT in intertemporal choice.

Highlights

Choices are often intertemporal, requiring trade-offs between short-term and long-term outcomes
As in the original ANOVA, there was a main effect of Condition (F1,47 = 33.84, p = 0.000001, partial η2 = 0.42), and no Group x Condition interaction (F1,47 = 2.89, p = 0.095, partial η2 = 0.05), confirming reduced delay discounting (DD) rates in the episodic future thinking (EFT) compared to the Standard condition in both Ventromedial prefrontal cortex (vmPFC) patients and controls
The present study investigated the effect of vmPFC damage on DD and its responsivity to reward magnitude and cues to imagine personal future events

Summary

Introduction

Choices are often intertemporal, requiring trade-offs between short-term and long-term outcomes. Human and non-human animals tend to prefer smaller-immediate over largerdelayed rewards (Green and Myerson, 2004; Rudebeck et al, 2006) This phenomenon reflects delay discounting (DD), the decrease in subjective value of a reward as the delay until its receipt increases. According to a prominent model of intertemporal choice (Hare et al, 2009; Figner et al, 2010; Peters and Büchel, 2011), vmPFC is engaged in reward valuation and integrates different outcome attributes (e.g., amounts, delays), whereas lateral prefrontal cortex modulates vmPFC subjective value signals to promote self-control and future-oriented choice. As in the original ANOVA, there was a main effect of Condition (F1,47 = 33.84, p = 0.000001, partial η2 = 0.42), and no Group x Condition interaction (F1,47 = 2.89, p = 0.095, partial η2 = 0.05), confirming reduced DD rates in the EFT compared to the Standard condition in both vmPFC patients and controls. There were no other significant effects (all ps > 0.23)

Discussion

Participants

Materials and methods

Results