Early lesion study showed that patients with damage within the episodic memory system, including the medial temporal lobe (MTL), had deficits in future imagination (Tulving, 2002). 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.Įpisodic memory has been conceived as a system that enables people to recollect past experiences. 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). Neuroimaging studies addressing the modulation effect through future imagination have revealed an association between DD reductions and increased brain activity in medial prefrontal valuation areas (Peters and Büchel, 2010 Benoit et al., 2011). Behavioral modulations such as future imagination have been shown to reduce individual discount rates in both healthy young subjects and patients (Ungemach et al., 2011 Cheng et al., 2012 Daniel et al., 2013 Lin and Epstein, 2014 Dassen et al., 2016). Individual differences in DD have been shown to relate to health-related behavior such as substance abuse (Kirby et al., 1999), gambling (Dixon et al., 2003), or overeating (Weller et al., 2008).Ī growing body of evidence has considered DD as a target for interventional therapies, in the hope for the treatment of diseases through changes of discount rates (Koffarnus et al., 2013). This phenomenon impacts a large variety of everyday decisions, related to health, finance and education. 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.ĭelay 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 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. These changes in functional connectivity are also associated with episodic memory capacity. 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. 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. Behavioral results replicate previous findings of a reduced discount rate in the DD plus imagination condition compared to the DD only condition. Subjects' episodic memory capacity was also assessed. ![]() 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. 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. It was assumed that cortical areas contribute to the modulation effect during the later period of imagination. This study examined whether elaborative future imagination modulated DD, and if so, what are the underlying neural substrates. Future imagination involves an initial period of construction and a later period of elaboration, with the more elaborative latter period recruiting more cortical regions. ![]() 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). ![]() Delay discounting (DD) refers to the phenomenon that individuals discount future consequences.
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