Episodic specificity induction impacts activity in a core brain network during construction of imagined future experiences

Abstract

Recent behavioral work suggests that an episodic specificity induction-brief training in recollecting the details of a past experienceenhances performance on subsequent tasks that rely on episodic retrieval, including imagining future experiences, solving open-ended problems, and thinking creatively. Despite these far-reaching behavioral effects, nothing is known about the neural processes impacted by an episodic specificity induction. Related neuroimaging work has linked episodic retrieval with a core network of brain regions that supports imagining future experiences. We tested the hypothesis that key structures in this network are influenced by the specificity induction. Participants received the specificity induction or one of two control inductions and then generated future events and semantic object comparisons during fMRI scanning. After receiving the specificity induction compared with the control, participants exhibited significantly more activity in several core network regions during the construction of imagined events over object comparisons, including the left anterior hippocampus, right inferior parietal lobule, right posterior cingulate cortex, and right ventral precuneus. Inductionrelated differences in the episodic detail of imagined events significantly modulated induction-related differences in the construction of imagined events in the left anterior hippocampus and right inferior parietal lobule. Resting-state functional connectivity analyses with hippocampal and inferior parietal lobule seed regions and the rest of the brain also revealed significantly stronger core network coupling following the specificity induction compared with the control. These findings provide evidence that an episodic specificity induction selectively targets episodic processes that are commonly linked to key core network regions, including the hippocampus.episodic specificity induction | imagination | hippocampus | core network | fMRI N umerous recent studies have revealed striking overlap in the neural and cognitive processes that support remembering past experiences and imagining future experiences or novel scenes (reviewed in refs. 1, 2). According to the constructive episodic simulation hypothesis (3), similarities between remembering and imagining reflect to a large extent the contributions of episodic memory to both processes (4). However, some evidence indicates that these similarities can also reflect the influence of nonepisodic processes, such as descriptive ability or narrative style, that influence remembering and imagining (5).We recently developed an experimental approach to distinguishing episodic and nonepisodic influences on remembering and imagining that we refer to as an episodic specificity induction: brief training in recollecting episodic details of recent experiences (reviewed in ref. 6). After receiving an episodic specificity induction (vs. a control induction), participants subsequently remembered past and imagined future experiences with increased episodic but not semantic detail, and the ...

Imagining the future: The core episodic simulation network dissociates as a function of timecourse and the amount of simulated information

“…That is, these effects are analogous to findings of transient episodic memory-related activity within the hippocampus (Vilberg & Rugg, 2012). Because these simulation effects closely correspond to those observed during memory, we adopt a similar interpretation and suggest that the transient hippocampal effects reflect the initial retrieval and reinstatement of episodic details (see, Addis et al, 2007; Madore et al, 2016; Rugg et al, 2015; Schacter & Addis, 2007). …”

“…In addition, if the hippocampus provides the initial access to episodic details not only during memory but also during simulation (see, Addis & Schacter, 2012; Schacter & Addis, 2007), its activity should demonstrate a transient profile. In support of this prediction, previous studies have shown that hippocampal activity increases during the initial construction of an imagined event (Addis, Wong, & Schacter, 2007; Addis, Cheng, Roberts, & Schacter, 2011a; Gaesser et al, 2013; Madore, Szpunar, Addis, & Schacter, 2016). These findings provide support for the idea that at least part of the hippocampal contribution to episodic simulation involves processes that support access to and/or retrieval of episodic details.…”

Episodic and semantic content of memory and imagination: A multilevel analysis

“…The episodic specificity induction did not alter the overall relationship between internal and external details, meaning that if the generation of external details is entirely a secondary by-product of amount of internal details (or vice versa), a reciprocal effect between the two should be observed. However, it has previously been shown that in most experiments the episodic specificity induction increases internal details, but does not decrease external details (Madore et al, 2014; Madore, Jing, et al, 2016; Madore & Schacter, 2014, 2016; Madore, Szpunar, Addis, & Schacter, 2016; but see Jing, Madore, & Schacter, 2016; Madore, Addis, & Schacter, 2015). Furthermore, different types of future imaginations can alter the amount of internal details generated, with no concurrent effects on external details (de Vito, Neroni, Gamboz, Della Sala, & Brandimonte, 2015; see also Neroni, Gamboz, De Vito, & Brandimonte, 2016), and age-related decreases in internal details have been reported even when the number of external details does not differ with age (Madore & Schacter, 2014; Zavagnin et al, 2016).…”

Episodic future thinking: mechanisms and functions

“…The ESI procedure described earlier in behavioral experiments was recently applied to the analysis of neural mechanisms in an fMRI study in which participants were scanned as they imagined possible future experiences following either an ESI or a control induction (56). Participants exhibited significantly more activity in several core network regions during the construction of imagined events after the ESI than control induction.…”