Mental simulation of routes during navigation involves adaptive temporal compression

Peering into the future: Eye movements predict neural repetition effects during episodic simulation

Imagining future scenarios involves recombining different elements of past experiences into a coherent event, a process broadly supported by the brain's default network. Prior work suggests that distinct brain regions may contribute to the inclusion of different simulation features. Here we examine how activity in these brain regions relates to the vividness of future simulations. Thirty-four healthy young adults imagined future events with familiar people and locations in a two-part study involving a repetition suppression paradigm. First, participants imagined events while their eyes were tracked during a behavioral session. Immediately after, participants imagined events during MRI scanning. The events to be imagined were manipulated such that some were identical to those imagined in the behavioral session while others involved new locations, new people, or both. In this way, we could examine how self-report ratings and eye movements predict brain activity during simulation along with specific simulation features. Vividness ratings were negatively correlated with eye movements, in contrast to an often-observed positive relationship with past recollection. Moreover, fewer eye movements predicted greater involvement of the hippocampus during simulation, an effect specific to location features. Our findings suggest that eye movements may facilitate scene construction for future thinking, lending support to frameworks that spatial information forms the foundation of episodic simulation.

Memory-related processing is the primary driver of human hippocampal theta oscillations

Decades of work in rodents suggest that movement is a powerful driver of hippocampal low-frequency "theta" oscillations. Puzzlingly, such movement-related theta increases in primates are less sustained and of lower frequency, leading to questions about their functional relevance. Verbal memory encoding and retrieval lead to robust increases in low-frequency oscillations in humans, and one possibility is that memory might be a stronger driver of hippocampal theta oscillations in humans than navigation. Here, neurosurgical patients navigated routes and then immediately mentally simulated the same routes while undergoing intracranial recordings. We found that mentally simulating the same route that was just navigated elicited oscillations that were of greater power, higher frequency, and longer duration than those involving navigation. Our findings suggest that memory is a more potent driver of human hippocampal theta oscillations than navigation, supporting models of internally generated theta oscillations in the human hippocampus.

A new understanding of the cognitive reappraisal technique: an extension based on the schema theory

Cognitive reappraisal is a widely utilized emotion regulation strategy that involves altering the personal meaning of an emotional event to enhance attention to emotional responses. Despite its common use, individual differences in cognitive reappraisal techniques and the spontaneous recovery, renewal, and reinstatement of negative responses across varying contexts may limit its effectiveness. Furthermore, detached reappraisal could cause distress for clients. According to Gross's theory, cognitive reappraisal is an effortless process that can occur spontaneously. When guided language triggers cognitive reappraisal as an emotion regulation strategy in laboratory or counseling settings, clients experience improved emotional states, but this induced strategy may not necessarily guide them in regulating emotions in similar future situations. Therefore, effectively applying cognitive reappraisal techniques in clinical practice to help clients alleviate emotional distress in daily life remains a significant concern. Exploring the mechanism of cognitive reappraisal reveals that reconstructing stimulus meaning is akin to extinction learning, which entails fostering cognitive contingency that the original stimulus provoking negative emotions will no longer result in negative outcomes in the current context. However, extinction learning is a new learning process rather than an elimination process. The activation of new learning relies on the presentation of critical cues, with contextual cues often playing a vital role, such as a safe laboratory or consulting room environment. We propose a new understanding of cognitive reappraisal based on the schema theory and the dual-system theory, emphasizing the significance of environmental interaction and feedback in constructing new experiences and updating schemata. This approach ultimately enriches the schema during training and integrates the new schema into long-term memory. Bottom-up behavioral experiences as schema enrichment training provide the foundation for top-down regulation to function. This method can assist clients in activating more suitable schemata probabilistically when encountering stimuli in real life, forming stable emotions, and achieving transfer and application across diverse contexts.

Representational dynamics of memories for real-life events

The continuous flow of experience that characterizes real-life events is not recorded as such in episodic memory but is condensed as a succession of event segments separated by temporal discontinuities. To unravel the neural basis of this representational structure, we recorded real-life events using wearable camera technology and used fMRI to investigate brain activity during their temporal unfolding in memory. We found that, compared to the representation of static scenes in memory, dynamically unfolding memory representations were associated with greater activation of the posterior medial episodic network. Strikingly, by analyzing the autocorrelation of brain activity patterns at successive time points throughout the retrieval period, we found that this network showed higher temporal dynamics when recalling events that included a higher density of event segments. These results reveal the key role of the posterior medial network in representing the dynamic unfolding of the event segments that constitute real-world memories.

From remembering to reconstruction: The transformative neural representation of episodic memory

Although memory has long been recognized as a generative process, neural research of memory in recent decades has been predominantly influenced by Tulving's "mental time traveling" perspective and focused on the reactivation and consolidation of encoded memory representations. With the development of multiple powerful analytical approaches to characterize the contents and formats of neural representations, recent studies are able to provide detailed examinations of the representations at various processing stages and have provided exciting new insights into the transformative nature of episodic memory. These studies have revealed the rapid, substantial, and continuous transformation of memory representation during the encoding, maintenance, consolidation, and retrieval of both single and multiple events, as well as event sequences. These transformations are characterized by the abstraction, integration, differentiation, and reorganization of memory representations, enabling the long-term retention and generalization of memory. These studies mark a significant shift in perspective from remembering to reconstruction, which might better reveal the nature of memory and its roles in supporting more effective learning, adaptive decision-making, and creative problem solving.

Future thinking to decrease real-world drinking in alcohol use disorder: Repairing reinforcer pathology in a randomized proof-of-concept trial

Reinforcer Pathology theory proposes that expanding the temporal window of reinforcement (i.e., reducing delay discounting) using episodic future thinking (EFT) would decrease alcohol consumption. However, evidence of effectiveness in real-world settings is lacking. Using a randomized proof-of-concept field trial, the current study examined the effect of expanding the temporal window of reinforcement, using remotely delivered EFT, on decreasing real-world alcohol consumption among individuals with alcohol use disorder (AUD). Fifty-two individuals (9 females) aged 18-65 years who met the DSM-5 criteria for moderate or severe AUD and aimed to drink in moderation or abstain from drinking completed the study and were included in analysis. EFT significantly (p = .031) reduced alcohol consumption (mean change of consumption pre-post intervention = -2.18 drinks/day) compared to control episodic recent thinking (ERT; mean change of -0.52 drinks/day). Changes in discounting rates pre-post intervention significantly predicted changes in alcohol consumption (coef. = .424, 95% CI [.043-.813], p = .030) even after controlling for age, gender, race, income, education, marital status, and family history of addiction. Overall satisfaction across groups was rated as 3.92 on a 1 to 5-point scale, suggesting that the current remote approach is feasible and acceptable. The current findings were congruent with the theory, Reinforcer Pathology, that EFT expands the temporal window and decreases alcohol consumption, and the remote approach was considered feasible and acceptable. We believe the present study contributes new knowledge with tangible benefits for scientifically understanding and better defining novel interventions that may be clinically deployed to improve treatment outcomes. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Temporal self-compression: Behavioral and neural evidence that past and future selves are compressed as they move away from the present

For centuries, great thinkers have struggled to understand how people represent a personal identity that changes over time. Insight may come from a basic principle of perception: as objects become distant, they also become less discriminable or “compressed.” In Studies 1–3, we demonstrate that people’s ratings of their own personality become increasingly less differentiated as they consider more distant past and future selves. In Study 4, we found neural evidence that the brain compresses self-representations with time as well. When we peer out a window, objects close to us are in clear view, whereas distant objects are hard to tell apart. We provide evidence that self-perception may operate similarly, with the nuance of distant selves increasingly harder to perceive.

A basic principle of perception is that as objects increase in distance from an observer, they also become logarithmically compressed in perception (i.e., not differentiated from one another), making them hard to distinguish. Could this basic principle apply to perhaps our most meaningful mental representation: our own sense of self? Here, we report four studies that suggest selves are increasingly non-discriminable with temporal distance from the present as well. In Studies 1 through 3, participants made trait ratings across various time points in the past and future. We found that participants compressed their past and future selves, relative to their present self. This effect was preferential to the self and could not be explained by the alternative possibility that individuals simply perceive arbitrary self-change with time irrespective of temporal distance. In Study 4, we tested for neural evidence of temporal self-compression by having participants complete trait ratings across time points while undergoing functional MRI. Representational similarity analysis was used to determine whether neural self-representations are compressed with temporal distance as well. We found evidence of temporal self-compression in areas of the default network, including medial prefrontal cortex and posterior cingulate cortex. Specifically, neural pattern similarity between self-representations was logarithmically compressed with temporal distance. Taken together, these findings reveal a “temporal self-compression” effect, with temporal selves becoming increasingly non-discriminable with distance from the present.

Mental Simulation to Promote Exercise Intentions and Behaviors

Mental simulation, which employs specific patterns of imagery, can increase the intention to exercise as well as actual engagement in exercise. The present studies explored the effects of mental simulation on the intention to engage in exercise while regulating emotions. The first study confirmed that mental simulation did promote intentions of participants. The second found that video-primed mental simulation was a more effective method of exercise intention promotion than semantic-primed and image-primed mental simulation. In the third study, it was found that combining process-based and outcome-based mental simulations increased exercise intentions. Positive emotions mediated imagery ability and intention to exercise. The final study found that the mental simulation interventions most effective for exercise adherence were those that balanced the valence of process and outcome components in such a way that a challenging process results in a positive outcome, or a smooth process results in a negative outcome. Each of these results has practical implications for exercise interventions that will be discussed.

Slices of the past: how events are temporally compressed in episodic memory

Remembering everyday events typically takes less time than the actual duration of the retrieved episodes, a phenomenon that has been referred to as the temporal compression of events in episodic memory. Here, we review recent studies that have shed light on how this compression mechanism operates. The evidence suggests that the continuous flow of experience is not represented as such in episodic memory. Instead, the unfolding of events is recalled as a succession of moments or slices of past experience that includes temporal discontinuities-portions of past experience are omitted when remembering. Consequently, the rate of event compression is not constant but depends on the density of recalled segments of past experience.

Static internal representation of dynamic situations reveals time compaction in human cognition

Introduction

The human brain has evolved under the constraint of survival in complex dynamic situations. It makes fast and reliable decisions based on internal representations of the environment. Whereas neural mechanisms involved in the internal representation of space are becoming known, entire spatiotemporal cognition remains a challenge. Growing experimental evidence suggests that brain mechanisms devoted to spatial cognition may also participate in spatiotemporal information processing.

Objectives

The time compaction hypothesis postulates that the brain represents both static and dynamic situations as purely static maps. Such an internal reduction of the external complexity allows humans to process time-changing situations in real-time efficiently. According to time compaction, there may be a deep inner similarity between the representation of conventional static and dynamic visual stimuli. Here, we test the hypothesis and report the first experimental evidence of time compaction in humans.

Methods

We engaged human subjects in a discrimination-learning task consisting in the classification of static and dynamic visual stimuli. When there was a hidden correspondence between static and dynamic stimuli due to time compaction, the learning performance was expected to be modulated. We studied such a modulation experimentally and by a computational model.

Results

The collected data validated the predicted learning modulation and confirmed that time compaction is a salient cognitive strategy adopted by the human brain to process time-changing situations. Mathematical modelling supported the finding. We also revealed that men are more prone to exploit time compaction in accordance with the context of the hypothesis as a cognitive basis for survival.

Conclusions

The static internal representation of dynamic situations is a human cognitive mechanism involved in decision-making and strategy planning to cope with time-changing environments. The finding opens a new venue to understand how humans efficiently interact with our dynamic world and thrive in nature.

Transforming the Concept of Memory Reactivation

Reactivation refers to the phenomenon wherein patterns of neural activity expressed during perceptual experience are re-expressed at a later time, a putative neural marker of memory. Reactivation of perceptual content has been observed across many cortical areas and correlates with objective and subjective expressions of memory in humans. However, because reactivation emphasizes similarities between perceptual and memory-based representations, it obscures differences in how perceptual events and memories are represented. Here, we highlight recent evidence of systematic differences in how (and where) perceptual events and memories are represented in the brain. We argue that neural representations of memories are best thought of as spatially transformed versions of perceptual representations. We consider why spatial transformations occur and identify critical questions for future research.

Environmental overlap and individual encoding strategy modulate memory interference in spatial navigation

There has been great interest in how previously acquired knowledge interacts with newly learned knowledge and how prior knowledge facilitates semantic and "schema" learning. In studies of episodic memory, it is broadly associated with interference. Very few studies have examined the balance between interference and facilitation over the course of temporally-extended events and its individual differences. In the present study, we recruited 120 participants for a two-day spatial navigation experiment, wherein participants on Day 2 navigated virtual routes that were learned from Day 1 while also learning new routes. Critically, half of the new mazes overlapped with the old mazes, while the other half did not, enabling us to examine interference and facilitation in the context of spatial episodic learning. Overall, we found that navigation performance in new mazes that overlapped with previously-learned routes was significantly worse than the new non-overlapping mazes, suggesting proactive interference. Interestingly, we found memory facilitation for new routes in familiar environments in locations where there was no direct overlap with the previously-learned routes. Cognitive map accuracy positively correlated with proactive interference. Moreover, participants with high self-report spatial ability and/or a preference for place-based learning experienced more proactive interference. Taken together, our results show that 1) both memory interference and facilitation can co-occur as a function of prior learning, 2) proactive interference within a route varied as a function of the degree of overlap with old knowledge, and 3) individual differences in spatial ability and strategy can modulate proactive interference.

The temporal compression of events during episodic future thinking

While the cognitive and neural mechanisms that underlie episodic future thinking are increasingly well understood, little is known about how the temporal unfolding of events is represented in future simulations. In this study, we leveraged wearable camera technology to examine whether real-world events are structured and compressed in the same way when imagining the future as when remembering the past. We found that future events were simulated at proportionally higher speed than past events and that the density of experience units representing the unfolding of events was lower for future than for past episodes. Despite these differences, the nature of events influenced compression rates in the same way for past and future events. Furthermore, the perceived duration of both types of events depended on the density of represented experience units. These results provide novel insight into the mechanisms that structure the unfolding of events during future simulations.

Sequence Memory in the Hippocampal-Entorhinal Region

Episodic memories are constructed from sequences of events. When recalling such a memory, we not only recall individual events, but we also retrieve information about how the sequence of events unfolded. Here, we focus on the role of the hippocampal-entorhinal region in processing and remembering sequences of events, which are thought to be stored in relational networks. We summarize evidence that temporal relations are a central organizational principle for memories in the hippocampus. Importantly, we incorporate novel insights from recent studies about the role of the adjacent entorhinal cortex in sequence memory. In rodents, the lateral entorhinal subregion carries temporal information during ongoing behavior. The human homologue is recruited during memory recall where its representations reflect the temporal relationships between events encountered in a sequence. We further introduce the idea that the hippocampal-entorhinal region might enable temporal scaling of sequence representations. Flexible changes of sequence progression speed could underlie the traversal of episodic memories and mental simulations at different paces. In conclusion, we describe how the entorhinal cortex and hippocampus contribute to remembering event sequences-a core component of episodic memory.

Stress Disrupts Human Hippocampal-Prefrontal Function during Prospective Spatial Navigation and Hinders Flexible Behavior

The ability to anticipate and flexibly plan for the future is critical for achieving goal-directed outcomes. Extant data suggest that neural and cognitive stress mechanisms may disrupt memory retrieval and restrict prospective planning, with deleterious impacts on behavior. Here, we examined whether and how acute psychological stress influences goal-directed navigational planning and efficient, flexible behavior. Our methods combined fMRI, neuroendocrinology, and machine learning with a virtual navigation planning task. Human participants were trained to navigate familiar paths in virtual environments and then (concurrent with fMRI) performed a planning and navigation task that could be most efficiently solved by taking novel shortcut paths. Strikingly, relative to non-stressed control participants, participants who performed the planning task under experimentally induced acute psychological stress demonstrated (1) disrupted neural activity critical for mnemonic retrieval and mental simulation and (2) reduced traversal of shortcuts and greater reliance on familiar paths. These neural and behavioral changes under psychological stress were tied to evidence for disrupted neural replay of memory for future locations in the spatial environment, providing mechanistic insight into why and how stress can alter planning and foster inefficient behavior.

Zooming In and Out on One's Life: Autobiographical Representations at Multiple Time Scales

The ability to decouple from the present environment and explore other times is a central feature of the human mind. Research in cognitive psychology and neuroscience has shown that the personal past and future is represented at multiple timescales and levels of resolution, from broad lifetime periods that span years to short-time slices of experience that span seconds. Here, I review this evidence and propose a theoretical framework for understanding mental time travel as the capacity to flexibly navigate hierarchical layers of autobiographical representations. On this view, past and future thoughts rely on two main systems-event simulation and autobiographical knowledge-that allow us to represent experiential contents that are decoupled from sensory input and to place these on a personal timeline scaffolded from conceptual knowledge of the content and structure of our life. The neural basis of this cognitive architecture is discussed, emphasizing the possible role of the medial pFC in integrating layers of autobiographical representations in the service of mental time travel.

Do questionnaires reflect their purported cognitive functions?

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Imagery and navigation questionnaires reflect their purported cognitive functions.

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Memory questionnaires reflect autobiographical memory vividness.

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Episodic details and memory questionnaires measure different aspects of memory.

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Imagery questionnaires also correlated with memory vividness and future thinking.

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Single questions modelled performance comparably to established questionnaires.

Questionnaires are used widely across psychology and permit valuable insights into a person’s thoughts and beliefs, which are difficult to derive from task performance measures alone. Given their importance and widespread use, it is vital that questionnaires map onto the cognitive functions they purport to reflect. However, where performance on naturalistic tasks such as imagination, autobiographical memory, future thinking and navigation is concerned, there is a dearth of knowledge about the relationships between task performance and questionnaire measures. Questionnaires are also typically designed to probe a specific aspect of cognition, when instead researchers sometimes want to obtain a broad profile of a participant. To the best of our knowledge, no questionnaire exists that asks simple single questions about a wide range of cognitive functions. To address these gaps in the literature, we recruited a large sample of participants (n = 217), all of whom completed a battery of widely used questionnaires and performed naturalistic tasks involving imagination, autobiographical memory, future thinking and navigation. We also devised a questionnaire that comprised simple single questions about the cognitive functions of interest. There were four main findings. First, imagination and navigation questionnaires reflected performance on their related tasks. Second, memory questionnaires were associated with autobiographical memory vividness and not internal (episodic) details. Third, imagery questionnaires were more associated with autobiographical memory vividness and future thinking than the questionnaires purporting to reflect these functions. Finally, initial exploratory analyses suggested that a broad profile of information can be obtained efficiently using a small number of simple single questions, and these modelled task performance comparably to established questionnaires in young, healthy adults. Overall, while some questionnaires can act as proxies for behaviour, the relationships between memory and future thinking tasks and questionnaires are more complex and require further elucidation.

The hippocampus contributes to temporal duration memory in the context of event sequences: A cross-species perspective

Although a large body of research has implicated the hippocampus in the processing of memory for temporal duration, there is an exigent degree of inconsistency across studies that obfuscates the precise contributions of this structure. To shed light on this issue, the present review article surveys both historical and recent cross-species evidence emanating from a wide variety of experimental paradigms, identifying areas of convergence and divergence. We suggest that while factors such as time-scale (e.g. the length of durations involved) and the nature of memory processing (e.g. prospective vs. retrospective memory) are very helpful in the interpretation of existing data, an additional important consideration is the context in which the duration information is experienced and processed, with the hippocampus being preferentially involved in memory for durations that are embedded within a sequence of events. We consider the mechanisms that may underpin temporal duration memory and how the same mechanisms may contribute to memory for other aspects of event sequences such as temporal order.

Multiple scales of valence processing in the brain

Psychological theories posit that affective experiences can be decomposed into component constituents, yet disagree on the level of representation of these components. Affective experiences have been previously described as emerging from core dimensions of valence and arousal. However, this view needs to be reconciled with accounts of valence processing in appetitive and aversive circuits from the neuroscience literature. Here we offer an account of affect that allows for both perspectives but compares across levels of analysis. At one level of analysis, valence and arousal are observed already in the properties of encountered stimuli and the appetitive and aversive neural circuits that engage accordingly. At another level of analysis, the explicit experiential aspect of affective processes are compressed and appraised in a manner that allows these experiences to be organized along valence and arousal axes. We review both the behavioral neuroscience evidence on appetitive and aversive circuits as well as the cognitive neuroscience literature on compression in information coding across multiple domains of processing. We argue that these processes are domain-general and adapt these principles to provide a perspective on how valence can be represented at multiple scales in the brain.

Spontaneous Activation of Event Details in Episodic Future Simulation

Episodic future simulation is supported by both the retrieval and recombination of episodic details. It remains unclear, however, how individuals retrieve episodic details from memory to construct possible future scenarios; for this people must use details related to the planned future events appropriately. A potentially relevant cognitive process is the spontaneous activation of intention observed in prospective memory (i.e., the intention superiority effect). Previous studies on prospective memory have shown that the approximation of retrieval opportunities for future intentions activate related information, suggesting that the intention superiority effect is context-sensitive. We hypothesized that the same cognitive process underlies future simulation—that is, details related to future events should spontaneously become activated at the appropriate moment of future simulation to make that simulation plausible. In Experiment 1, participants took part in future experiments and formed intentions to perform particular actions for the next experiments. Subsequently, they imagined events that could occur up until they arrived at the experimental room on the day of the next experiment. During this exercise, they did not imagine engaging in the required experimental task. We measured the conceptual activation of intention-related information via a recognition task using intended action words as targets. The results showed the intention superiority effect—concepts related to participants’ future intentions became active when envisioning future events approaching the next experiment. In Experiments 2 and 3, we ensured that the intention superiority effect in future simulation was context-sensitive by adding a control condition that required participants to imagine events other than the approaching future experiments. These results indicated that concepts related to the intended actions were spontaneously activated when imagined future events became both temporally and spatially close to the future simulation. Our finding suggests that spontaneous activation of details approaching the context of a future simulation helps in constructing plausible future scenarios.

Human spatial representation: what we cannot learn from the studies of rodent navigation

Studies of human and rodent navigation often reveal a remarkable cross-species similarity between the cognitive and neural mechanisms of navigation. Such cross-species resemblance often overshadows some critical differences between how humans and nonhuman animals navigate. In this review, I propose that a navigation system requires both a storage system (i.e., representing spatial information) and a positioning system (i.e., sensing spatial information) to operate. I then argue that the way humans represent spatial information is different from that inferred from the cellular activity observed during rodent navigation. Such difference spans the whole hierarchy of spatial representation, from representing the structure of an environment to the representation of subregions of an environment, routes and paths, and the distance and direction relative to a goal location. These cross-species inconsistencies suggest that what we learn from rodent navigation does not always transfer to human navigation. Finally, I argue for closing the loop for the dominant, unidirectional animal-to-human approach in navigation research so that insights from behavioral studies of human navigation may also flow back to shed light on the cellular mechanisms of navigation for both humans and other mammals (i.e., a human-to-animal approach).

Dynamic Neural Network Reconfiguration During the Generation and Reinstatement of Mnemonic Representations

Mnemonic representations allow humans to re-experience the past or simulate future scenarios by integrating episodic features from memory. Theoretical models posit that mnemonic representations require dynamic processing between neural indexes in the hippocampus and areas of the cortex providing specialized information processing. However, it remains unknown whether global and local network topology varies as information is encoded into a mnemonic representation and subsequently reinstated. Here, we investigated the dynamic nature of memory networks while a representation of a virtual city is generated and reinstated during mental simulations. We find that the brain reconfigures from a state of heightened integration when encoding demands are highest, to a state of localized processing once representations are formed. This reconfiguration is associated with changes in hippocampal centrality at the intra- and inter-module level, decreasing its role as a connector hub between modules and within a hippocampal neighborhood as encoding demands lessen. During mental simulations, we found increased levels of hippocampal centrality within its local neighborhood coupled with decreased functional interactions between other regions of the neighborhood during highly vivid simulations, suggesting that information flow vis-à-vis the hippocampus is critical for high fidelity recapitulation of mnemonic representations.

Event segmentation and the temporal compression of experience in episodic memory

Recent studies suggest that episodic memory represents the continuous flow of information that constitutes daily life events in a temporally compressed form, but the nature and determinants of this compression mechanism remain unclear. In the present study, we used wearable camera technology to investigate whether the temporal compression of experience in episodic memory depends on event segmentation. Participants experienced a series of events during a walk on a university campus and were later asked to mentally replay these events. The temporal compression of events in memory and grain size of event segmentation were estimated based on records of participants' experience taken by the camera. The results showed that the temporal compression of events in memory (i.e., the density of recalled moments of experience per unit of time of the actual event duration) closely corresponded to the grain size of event segmentation. Specifically, grain sizes of event segmentation and temporal compression rates were four to five times lower when remembering events that involved goal-directed actions compared to other kinds of events (e.g., spatial displacements). Furthermore, temporal compression rates in memory were significantly predicted by the grain size of event segmentation and event boundaries were more than five times more likely to be remembered than other parts of events. Together, these results provide new insights into the mechanism of temporal compression of events in episodic memory.

The time to remember: Temporal compression and duration judgements in memory for real-life events

Recent studies suggest that the continuous flow of information that constitutes daily life events is temporally compressed in episodic memory, yet the characteristics and determinants of this compression mechanism remain unclear. This study examined this question using an experimental paradigm incorporating wearable camera technology. Participants experienced a series of real-life events and were later asked to mentally replay various event sequences that were cued by pictures taken during the original events. Estimates of temporal compression (the ratio of the time needed to mentally re-experience an event to the actual event duration) showed that events were replayed, on average, about eight times faster than the original experiences. This compression mechanism seemed to operate by representing events as a succession of moments or slices of prior experience separated by temporal discontinuities. Importantly, however, rates of temporal compression were not constant and were lower for events involving goal-directed actions. The results also showed that the perceived duration of events increased with the density of recalled moments of prior experience. Taken together, these data extend our understanding of the mechanisms underlying the temporal compression and perceived duration of real-life events in episodic memory.

A rat in the sewer: How mental imagery interacts with object recognition

The role of mental imagery has been puzzling researchers for more than two millennia. Both positive and negative effects of mental imagery on information processing have been discussed. The aim of this work was to examine how mental imagery affects object recognition and associative learning. Based on different perceptual and cognitive accounts we tested our imagery-induced interaction hypothesis in a series of two experiments. According to that, mental imagery could lead to (1) a superior performance in object recognition and associative learning if these objects are imagery-congruent (semantically) and to (2) an inferior performance if these objects are imagery-incongruent. In the first experiment, we used a static environment and tested associative learning. In the second experiment, subjects encoded object information in a dynamic environment by means of a virtual sewer system. Our results demonstrate that subjects who received a role adoption task (by means of guided mental imagery) performed better when imagery-congruent objects were used and worse when imagery-incongruent objects were used. We finally discuss our findings also with respect to alternative accounts and plead for a multi-methodological approach for future research in order to solve this issue.

Oscillations, neural computations and learning during wake and sleep

Learning and memory theories consider sleep and the reactivation of waking hippocampal neural patterns to be crucial for the long-term consolidation of memories. Here we propose that precisely coordinated representations across brain regions allow the inference and evaluation of causal relationships to train an internal generative model of the world. This training starts during wakefulness and strongly benefits from sleep because its recurring nested oscillations may reflect compositional operations that facilitate a hierarchical processing of information, potentially including behavioral policy evaluations. This suggests that an important function of sleep activity is to provide conditions conducive to general inference, prediction and insight, which contribute to a more robust internal model that underlies generalization and adaptive behavior.

Interacting networks of brain regions underlie human spatial navigation: a review and novel synthesis of the literature

Navigation is an inherently dynamic and multimodal process, making isolation of the unique cognitive components underlying it challenging. The assumptions of much of the literature on human spatial navigation are that 1) spatial navigation involves modality independent, discrete metric representations (i.e., egocentric vs. allocentric), 2) such representations can be further distilled to elemental cognitive processes, and 3) these cognitive processes can be ascribed to unique brain regions. We argue that modality-independent spatial representations, instead of providing exact metrics about our surrounding environment, more often involve heuristics for estimating spatial topology useful to the current task at hand. We also argue that egocentric (body centered) and allocentric (world centered) representations are better conceptualized as involving a continuum rather than as discrete. We propose a neural model to accommodate these ideas, arguing that such representations also involve a continuum of network interactions centered on retrosplenial and posterior parietal cortex, respectively. Our model thus helps explain both behavioral and neural findings otherwise difficult to account for with classic models of spatial navigation and memory, providing a testable framework for novel experiments.

Temporal compression in episodic memory for real-life events

Remembering an event typically takes less time than experiencing it, suggesting that episodic memory represents past experience in a temporally compressed way. Little is known, however, about how the continuous flow of real-life events is summarised in memory. Here we investigated the nature and determinants of temporal compression by directly comparing memory contents with the objective timing of events as measured by a wearable camera. We found that episodic memories consist of a succession of moments of prior experience that represent events with varying compression rates, such that the density of retrieved information is modulated by goal processing and perceptual changes. Furthermore, the results showed that temporal compression rates remain relatively stable over one week and increase after a one-month delay, particularly for goal-related events. These data shed new light on temporal compression in episodic memory and suggest that compression rates are adaptively modulated to maintain current goal-relevant information.

Preparing for what might happen: An episodic specificity induction impacts the generation of alternative future events

A critical adaptive feature of future thinking involves the ability to generate alternative versions of possible future events. However, little is known about the nature of the processes that support this ability. Here we examined whether an episodic specificity induction - brief training in recollecting details of a recent experience that selectively impacts tasks that draw on episodic retrieval - (1) boosts alternative event generation and (2) changes one's initial perceptions of negative future events. In Experiment 1, an episodic specificity induction significantly increased the number of alternative positive outcomes that participants generated to a series of standardized negative events, compared with a control induction not focused on episodic specificity. We also observed larger decreases in the perceived plausibility and negativity of the original events in the specificity condition, where participants generated more alternative outcomes, relative to the control condition. In Experiment 2, we replicated and extended these findings using a series of personalized negative events. Our findings support the idea that episodic memory processes are involved in generating alternative outcomes to anticipated future events, and that boosting the number of alternative outcomes is related to subsequent changes in the perceived plausibility and valence of the original events, which may have implications for psychological well-being.

Episodic Future Thinking: Mechanisms and Functions

Episodic future thinking refers to the capacity to imagine or simulate experiences that might occur in one's personal future. Cognitive, neuropsychological, and neuroimaging research concerning episodic future thinking has accelerated during recent years. This article discusses research that has delineated cognitive and neural mechanisms that support episodic future thinking as well as the functions that episodic future thinking serves. Studies focused on mechanisms have identified a core brain network that underlies episodic future thinking and have begun to tease apart the relative contributions of particular regions in this network, and the specific cognitive processes that they support. Studies concerned with functions have identified several domains in which episodic future thinking produces performance benefits, including decision making, emotion regulation, prospective memory, and spatial navigation.

Contracted time and expanded space: The impact of circumnavigation on judgements of space and time

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Certain locations in the world can only be reached by circumnavigating obstacles.

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All travel times are underestimated and all distances are overestimated.

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Travel times are further compressed when circumnavigation is required.

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Distances are further expanded when circumnavigation is required.

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Temporal and spatial cognitive biases may be dissociable.

The ability to estimate distance and time to spatial goals is fundamental for survival. In cases where a region of space must be navigated around to reach a location (circumnavigation), the distance along the path is greater than the straight-line Euclidean distance. To explore how such circumnavigation impacts on estimates of distance and time, we tested participants on their ability to estimate travel time and Euclidean distance to learned destinations in a virtual town. Estimates for approximately linear routes were compared with estimates for routes requiring circumnavigation. For all routes, travel times were significantly underestimated, and Euclidean distances overestimated. For routes requiring circumnavigation, travel time was further underestimated and the Euclidean distance further overestimated. Thus, circumnavigation appears to enhance existing biases in representations of travel time and distance.

Familiarity expands space and contracts time

When humans draw maps, or make judgments about travel‐time, their responses are rarely accurate and are often systematically distorted. Distortion effects on estimating time to arrival and the scale of sketch‐maps reveal the nature of mental representation of time and space. Inspired by data from rodent entorhinal grid cells, we predicted that familiarity to an environment would distort representations of the space by expanding the size of it. We also hypothesized that travel‐time estimation would be distorted in the same direction as space‐size, if time and space rely on the same cognitive map. We asked international students, who had lived at a college in London for 9 months, to sketch a south‐up map of their college district, estimate travel‐time to destinations within the area, and mark their everyday walking routes. We found that while estimates for sketched space were expanded with familiarity, estimates of the time to travel through the space were contracted with familiarity. Thus, we found dissociable responses to familiarity in representations of time and space. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.