Weaving the Past into an Imagined Future: Episodic Future Thinking Relies on Working Memory as a Cognitive Interface with Episodic Memory
Hill, Paul Faxon
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Converging cognitive and neuroimaging evidence reveals that episodic memory and episodic future thinking (EFT) share component processes. Much less is known about the relationship between EFT and working memory (WM) processes. We hypothesized that WM capacity might provide a crucial componential cognitive role during EFT by supporting the translation of information from discrete episodic memories into a novel future event. We tested this hypothesis in two studies. In Study 1, we collected functional magnetic resonance imaging data during a dual-task interference paradigm that varied WM load and processing demands during EFT. Events imagined while actively maintaining bound item-location representations were less vivid than those imagined during low WM load control trials. Measures of functional and effective connectivity indicated that this behavioral effect corresponded with reduced coupling between the dorsomedial prefrontal cortex and right temporoparietal junction. Events imagined while simultaneously manipulating items in WM took longer to construct than events imagined during control trials and were associated with less functional coupling between the right hippocampus and posterior visuospatial regions. In Study 2, participants completed a similar WM dual-task while simultaneously recalling past events or imagining future events during scalp-recorded encephalography (EEG). As in Study 1, future events imagined while maintaining item-location representations were less vivid than control trials. This effect was specific to future events and corresponded to reduced theta reactivity over bilateral temporoparietal sites. Relative to episodic memory, EFT was associated with alpha synchronization over frontal and parietal sites as well as greater theta-gamma phase amplitude coupling in the right dorsolateral prefrontal cortex. In contrast, episodic memory was associated with greater cross-frequency coupling between frontal theta and occipital gamma oscillations. These results provide novel empirical support for previous theoretical accounts suggesting that WM capacity provides the cognitive workspace necessary to temporarily store and recombine details from discrete episodes into a future event representation.
- Doctoral Dissertations