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

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.

Keywords: decision making; delay discounting; episodic future thinking; human; neuroscience; reward; ventromedial prefrontal cortex.

Figure 1.. Location and overlap of brain lesions.

The panel shows the lesions of the 12 patients with ventromedial prefrontal cortex (vmPFC) damage projected on the same eight axial slices and on the mesial view of the standard Montreal Neurological Institute (MNI) brain. The level of the axial slices is indicated by horizontal lines on the mesial view of the brain, and by z-coordinates. The color bar indicates the number of overlapping lesions. Maximal overlap occurs in Brodmann areas (BAs) 11, 10, and 32 of vmPFC. In axial slices, the left hemisphere is on the left side.

Figure 2.. Example of an experimental trial in the episodic future thinking (EFT) condition.

Participants were presented with an episodic cue and asked to imagine a personal future experience occurring at a specific delay (e.g., in 1 year). They then were presented with two hypothetical reward amounts and indicated their choice between the smaller-immediate reward and the larger-delayed reward to be received at that delay.

Figure 3.. Subjective value as a function of delay by participant group and task condition.

Lines represent choices averaged across both reward amounts (data points available in the source data file: Figure 3—source data 1).

Figure 3—figure supplement 1.. Subjective value of small and large rewards as a function of delay for individual participants in the Standard and episodic future thinking (EFT) condition (data points available in the source data file: Figure 3—figure supplement 1—source data 1).

Figure 4.. Area under the empirical discounting curve (AuC) by participant group, task condition, and reward magnitude.

The figure reports individual participants’ data. Empty symbols denote ventromedial prefrontal cortex (vmPFC) patients with brain damage touching the lateral prefrontal cortex. *p < 0.05 (data points available in the source data file: Figure 4—source data 1).