Episodic simulation refers to the construction of imagined, hypothetical events that might occur in one's personal future. Damage to our capacity for episodic simulation can produce grave consequences, impairing our ability to anticipate, plan, and prepare for the future. New theoretical approaches have begun to uncover the cognitive and neural mechanisms underlying episodic simulation, but much remains to be examined. The purpose of this dissertation is to further investigate the mechanisms supporting episodic simulation as well as the functions it serves. In the first study of the dissertation I examine age-related deficits in imagining the future, remembering the past, and describing the present (Paper 1). These findings replicate known deficits in older adults in episodic simulation and memory, yet provide evidence of non-episodic processes that also shape their expression. I next examine component cognitive and neural processes that are recruited to generate imagined events (Paper 2). Distinct regions of the hippocampus were active when encoding, tracking novelty, or constructing imagined events, suggesting a multifaceted role of the hippocampus in supporting episodic simulation. Finally, I present evidence that episodic simulation and memory can be used to facilitate empathy, that is, intentions to help a person in need (Paper 3). People are more willing to help a person in need after imagining or remembering helping that individual. Furthermore, the episodic vividness of these imagined or remembered events heightened intentions to help. These findings elucidate a previously unconsidered mechanism for facilitating empathy, and, in doing so, open the possibility for a new functional account of episodic simulation. I close by discussing the promise of this line of work that aims to provide new insights into the relationship between episodic simulation, memory, and empathy. / Psychology

Goal-directed episodic simulation, the imaginative construction of a hypothetical personal event or series of events focused on a specific goal, is essential to our everyday lives. We often imagine how we could solve a problem or achieve a goal in the future, or how we could have avoided a misstep in the past, but many of the behavioral and neural mechanisms underlying such goal-directed simulations have yet to be explored. The three papers of this dissertation investigated the neural correlates of three types of future episodic simulations in Papers 1 and 2 and examined a fourth such simulation directed at past events as an adaptive, constructive process in Paper 3. Some research has associated default network activity with internally-focused, but not with goal-directed cognition. Papers 1 and 2 of this dissertation showed that regions of the default network could form functional networks with regions of the frontoparietal control network while participants imagined solving specific problems or going through a sequence of steps necessary to achieve a personal goal. When participants imagined events they associated with actually attaining a goal, default network regions flexibly coupled with reward-processing regions, providing evidence that the default network can join forces with other networks or components thereof to support goal-directed episodic simulations. Using two distinct paradigms with both young and older adults, Paper 3 focused on episodic counterfactual simulations of how past events could have turned out differently and tested whether counterfactual simulations could affect participants' memory of the original events. Our results revealed that episodic counterfactual simulations can act as a type of internally generated misinformation by causing source confusion between the original event and the imagined counterfactual outcome, especially in older adults. The findings of the three papers in this dissertation lay the groundwork for further research on the behavioral and neural mechanisms of goal-directed episodic simulations, as well as their adaptive functions and possible downsides. / Psychology

As humans we are not stuck in an everlasting present. Instead, we can project ourselves into both our personal past and future. Remembering the past and simulating the future are strongly interrelated processes. They are both supported by largely the same brain regions including the rostral and ventral medial prefrontal cortex (mPFC) but also the hippocampus, the posterior cingulate cortex (PCC), as well as other regions in the parietal and temporal cortices. Interestingly, this core network for episodic simulation and episodic memory partially overlaps with a brain network for evaluation and value-based decision making. This is particularly the case for the mPFC. This part of the brain has been associated both with a large number of different cognitive functions ranging from the representation of memory schemas and self-referential processing to the representation of value and affect. As a consequence, a unifying account of mPFC functioning has remained elusive. The present thesis investigates the unique contribution of the mPFC to episodic simulation by highlighting its role in the representation of memory schemas and value. In a first functional MRI and pre-registered behavioral replication study, we demonstrate that the mPFC encodes representations of known people as well as of known locations from participants’ everyday life. We demonstrate that merely imagined encounters with liked vs. disliked people at these locations can change our attitude toward the locations. The magnitude of this simulation-induced attitude change was predicted by activation in the mPFC during the simulations. Specifically, locations simulated with liked people exhibited significantly larger increases in liking than those simulated with disliked people. In a second behavioral study, we examined the mechanisms of simulation-based learning more closely. To this end, participants also simulated encounters with neutral people at neutral locations. Using repeated behavioral assessments of participants’ memory representations, we reveal that simulations cause an integration of memory representations for jointly simulated people and locations. Moreover, compared to the neutral baseline condition we demonstrate a transfer of positive valence from liked and of negative valence from disliked people to their paired locations. We also provide evidence that simulations induce an affective experience that aligns with the valence of the person and that this experience can account for the observed attitude change toward the location. In a final fMRI study, we examine the structure of memory representations encoded in the mPFC. Specifically, we provide evidence for the hypothesis that the mPFC encodes schematic representations of our social and physical environment. We demonstrate that representations of individual exemplars of these environments (i.e., individual people and locations) are closely intertwined with a representation of their value. In sum, our findings show that we can learn from imagined experience much as we learn from actual past experience and that the mPFC plays a key role in simulation-based learning. The mPFC encodes information about our environment in value-weighted schematic representations. These representations can account for the overlap of mnemonic and evaluative functions in the mPFC and might play a key role in simulation-based learning. Our results are in line with a view that our memories of the past serve us in ways that are oriented toward the future. Our ability to simulate potential scenarios allows us to anticipate the future consequences of our choices and thereby fosters farsighted decision making. Thus, our findings help to better characterize the functional role of the mPFC in episodic future simulation and valuation.

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