title: A Reduction in Delay Discounting by Using Episodic Future Imagination and the Association with Episodic Memory Capacity.
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.
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical Faculty, University of CologneCologne, Germany; Department of Psychiatry and Psychotherapy, University Hospital of BonnBonn, Germany.
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Psychiatry and Psychotherapy, University Hospital of Bonn Bonn, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Kleinschmidt
authors.affiliation: Department of Radiology, University Hospital of Bonn Bonn, Germany.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Martin
authors.affiliation: Department of Neurology, XuanWu Hospital of Capital Medical University Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical Faculty, University of Cologne Cologne, Germany.
authors.forename: Manuela
authors.initials: M
authors.lastname: Thelen
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical Faculty, University of Cologne Cologne, Germany.
authors.forename: Dix
authors.initials: D
authors.lastname: Meiberth
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical Faculty, University of CologneCologne, Germany; German Center for Neurodegenerative DiseasesBonn, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Jessen
authors.affiliation: Department of Epileptology, University Hospital of BonnBonn, Germany; Center for Economics and Neuroscience, University of BonnBonn, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Weber
keywords: anterior cingulate cortex; delay discounting; episodic future imagination; episodic memory capacity; left inferior parietal cortex; subjective value