Abstract
Delay discounting (DD) refers to the phenomenon that individuals discount future consequences. Previous studies showed that future imagination reduces DD, which was mediated by functional connectivity between medial prefrontal valuation areas and a key region for episodic memory (hippocampus). Future imagination involves an initial period of construction and a later period of elaboration, with the more elaborative latter period recruiting more cortical regions. This study examined whether elaborative future imagination modulated DD, and if so, what are the underlying neural substrates. It was assumed that cortical areas contribute to the modulation effect during the later period of imagination. Since future imagination is supported by episodic memory capacity, we additionally hypothesize that the neural network underlying the modulation effect is related to individual episodic memory capacity. Twenty-two subjects received an extensive interview on personal future events, followed by an fMRI DD experiment with and without the need to perform elaborative future imagination simultaneously. Subjects' episodic memory capacity was also assessed. Behavioral results replicate previous findings of a reduced discount rate in the DD plus imagination condition compared to the DD only condition. The behavioral effect positively correlated with: (i) subjective value signal changes in midline brain structures during the initial imagination period; and (ii) signal changes in left prefrontoparietal areas during the later imagination period. Generalized psychophysiological interaction (gPPI) analyses reveal positive correlations between the behavioral effect and functional connectivity among the following areas: right anterior cingulate cortex (ACC) and left hippocampus; left inferior parietal cortex (IPC) and left hippocampus; and left IPC and bilateral occipital cortices. These changes in functional connectivity are also associated with episodic memory capacity. A hierarchical multiple regression indicates that the model with both the valuation related signal changes in the right ACC and the imagination related signal changes in the left IPC best predicts the reduction in DD. This study illustrates interactions between the left hippocampus and multiple cortical regions underlying the modulation effect of elaborative episodic future imagination, demonstrating, for the first time, empirical support for a relation to individual episodic memory capacity.
Highlights
Delay discounting (DD) refers to the phenomenon that most people tend to discount future consequences when facing the intertemporal choice between a sooner smaller reward and a later larger reward (Ainslie, 1975; Frederick et al, 2002)
A lesion study (Berryhill et al, 2010) showed that patients with damage in prefrontal and parietal cortical regions were selectively impaired in the elaboration of the constructed events, but not the construction per se. These results indicated that the lateral prefrontal and parietal cortical regions have a unique contribution to the elaboration of the episodic future imagination
The current study demonstrated decreases of discount rates in an intertemporal choice task due to episodic future imagination
Summary
Delay discounting (DD) refers to the phenomenon that most people tend to discount future consequences when facing the intertemporal choice between a sooner smaller reward and a later larger reward (Ainslie, 1975; Frederick et al, 2002). Activation in the medial prefrontal cortex (mPFC) was found to interact with the hippocampus (Peters and Büchel, 2010; Benoit et al, 2011), a key region for episodic memory and episodic future imagination (Schacter and Addis, 2009). These reports suggest a hippocampal-mPFC pathway for this modulation effect: future imagination may increase the functional coupling between the hippocampus and the mPFC, changing the reward valuation process, and altering the representation of future rewards such that it may result in more future oriented choices. Following the suggestion that the hippocampal region may support decision-making through an interaction with cortical areas via multiple pathways (Buckner, 2010), we hypothesize that the hippocampus functionally interacts with multiple cortical areas during prolonged and elaborated future imagination by interacting with more cortical regions in the later period of imagination
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
