Effects of the perceived temporal distance of events on mental time travel and on its underlying brain circuits.

Mental Time Travel (MTT) allows us to remember past events and imagine future ones. According to previous literature, the Temporal Distance of events affects MTT: our ability to order events worsens for close, compared to far, events. However, those studies established distances a-priori, albeit the way we perceive events' temporal distance may subjectively differ from their objective distance. Thus, in the current study, we aimed to investigate the effects of Perceived Temporal Distance (PTD) on the MTT ability and the brain areas mediating this process. Thirty-three healthy volunteers took part in an fMRI MTT task. Participants were asked to project themselves into the past, present, or future, and to judge a series of events as relative-past or relative-future, in relation to the adopted time location. Outside the scanner, participants provided PTD estimates for each stimulus of the MTT task. Participants' performance and functional activity were analyzed as a function of these estimations. At the behavioural level, PTD predicts the modulation of the performance for relative-past and relative-future. Bilateral angular gyrus, retrosplenial cortex, temporo-parietal region and medial, middle and superior frontal gyri mediate the PTD effect. In addition to these areas, the closer the relative-future events are perceived, the higher the involvement of left parahippocampal and lingual gyri and right cerebellum. Thus, perceived proximity of events activates frontal and posterior parietal areas, which therefore might mediate the processing of PTD in the cognitive spatial representation of time. Future proximity also activates cerebellum and medial temporal areas, known to be involved in imaginative and constructive cognitive functions.

Mental Time Travel as Self-Affirmation.

ACADEMIC ABSTRACT: This article integrates and advances the scope of research on the role of mental time travel in bolstering the self. We propose that imagining the self in the future (prospection) or in the past (retrospection) highlights central and positive self-aspects. Thus, bringing to mind one's future or past broadens the perceived bases of self-integrity and offers a route to self-affirmation. In reviewing corresponding research programs on self-prospection and nostalgia, we illustrate that mental time travel serves to affirm the self in terms of self-esteem, coherence, and control. Mental time travel could be implemented as a source of self-affirmation for facilitating coping and behavior change in several domains such as relationships, health, education, and organizational contexts. PUBLIC ABSTRACT: People can mentally travel to their future or to their past. When people imagine what they will be like in the future, or what they were like in the past, they tend to think about themselves in terms of the important and positive attributes that they possess. Thinking about themselves in such an affirming way expands and consolidates their self-views. This broader image of themselves can increase self-esteem (the extent to which one likes who they are), coherence (the extent to which one perceives life as meaningful), and control (the extent to which one feels capable of initiating and pursuing goals or effecting desirable outcomes). Mental time travel, then, has favorable or affirming consequences for one's self-views. These consequences can be harnessed to modify one's behavior in such life domains as relationships, health, education, and work.

A preliminary experimental test of the crossed influences between the valence of collective memory and collective future thinking.

This research experimentally examined the crossed influences between the emotional valence of collective memory and collective future thinking. As remembering the past and imagining the future are shaped by the present, we additionally test whether perceived anomie (i.e., perceiving present society as disintegrated and disregulated) would moderate these influences. Study 1 (N = 228 French participants) manipulated the valence of collective memory (positive vs. negative French past) to test its effect on the valence of collective future thinking. Results showed that the salience of a negative (vs. positive) French past lead to the projection of a more negative French future only among participants who perceived present society as highly disregulated. Study 2 (N = 215) focused on the influence of the valence of collective future thinking (positive vs. negative French future) on the valence associated with the French past. Results showed that the salience of a negative (vs. positive) French future lead left-wing participants to rate more positively events/figures of the French past that are usually valued by conservatives. Taken together, these studies provided evidence of conditional effects in the crossed influences between the emotional valence of collective memory and collective future thinking, thus contributing to the recent literature on collective mental time travel.

Afterlife future thinking: imagining oneself beyond death.

Studies on episodic future thinking (the capacity to simulate possible experiences in one's personal future) have ignored future thinking that extends beyond death. We here examined personal afterlife projections in comparison with autobiographical memories and future projections in Thai (Study 1) and American (Study 2) samples. Participants reported all three types of events and rated their characteristics. In both studies, the characteristics of afterlife events were rated lower than those of memories and future events. Participants who believed in the afterlife generally rated afterlife events higher than non-believers and those who were uncertain, although this effect was most pronounced in Study 2. The content of afterlife events followed religious beliefs in the afterlife, and the majority of afterlife events were expected to take place immediately after death. The findings show that afterlife thoughts demonstrate characteristics that are comparable to memories and episodic future thoughts, and are shaped by religious beliefs.

Retrospective future thinking as a novel method to imagine the future: remembering autobiographical events from the perspective of the future self.

People think retrospectively about past events and prospectively about future events. Here, the novel method of retrospective future thinking is introduced to investigate the characteristics of autobiographical events reported as if they had been already experienced. In total, 166 participants were asked to (1) generate cultural life scripts and (2) to imagine themselves being 100-years old. From this perspective, they reported, dated and rated on valence their seven most important events. Results provide evidence that the cultural life script guides the recall and, more so, the imagination of retrospectively reported autobiographical events. Exploratory analysis of age effects indicated that older participants reported events that were more realistic, less scripted and wider distributed across the life span. This provides the first evidence that retrospective future thinking can alter older adults' life perspective by expanding their period for experiencing important events beyond the reminiscence bump years.

Episodic thought distinguishes spontaneous cognition in waking from REM and NREM sleep.

Evidence suggests continuity between cognition in waking and sleeping states. However, one type of cognition that may differ is episodic thoughts of the past and future. The current study investigated this across waking, NREM sleep and REM sleep. We analyzed thought reports obtained from a large sample of individuals (N = 138) who underwent experience-sampling during wakefulness as well as serial awakenings in sleep. Our data suggest that while episodic thoughts are common during waking spontaneous thought, episodic thoughts of both the past and the future rarely occur in either N2 or REM sleep. Moreover, replicating previous findings, episodic thoughts during wakefulness exhibit a strong prospective bias and frequently involve autobiographical planning. Together, these results suggest that the occurrence of spontaneous episodic thoughts differs substantially across waking and dreaming sleep states. We suggest that this points to a difference in the way that human consciousness is typically experienced across the sleep-wake cycle.

Effects of inhibitory control capacity and cognitive load on involuntary past and future thoughts: A laboratory study.

The present study focused on involuntary thoughts about personal past events (i.e., involuntary autobiographical memories; IAMs), and involuntary thoughts about future events and plans (i.e., involuntary future thoughts; IFTs). The frequency of these involuntary thoughts is influenced by cognitive demands of ongoing activities, but the exact underlying mechanism(s) has yet to be revealed. The present study tested two possible explanations: (1) the special inhibitory mechanism switches on when one is engaged in attentionally demanding activities; (2) different levels of cognitive load interfere with cue-noticing that act as triggers for IAMs and IFTs. We report a study with pre-selected groups of participants that differed in terms of their individual level of inhibitory control capacity (high vs. low), and completed both standard and attentionally demanding versions of a laboratory vigilance task with irrelevant cue-words to trigger IAMs and IFTs, and random thought-probes to measure their frequency. To examine the level of incidental cue-noticing, participants also completed an unexpected cue-recognition task. Despite large differences between groups in inhibitory control capacity, the number of IFTs and IAMs, reported in the attentionally demanding condition, was comparable. In addition, high cognitive load reduced the number of IAMs, but not IFTs. Finally, the recognition of incidental cues encountered in the vigilance task was reduced under high cognitive load condition, indicating that poor cue-noticing may be the main underlying mechanism of cognitive load effect rather than the lack of inhibitory resources needed to suppress involuntary retrieval. This and other possible mechanisms and avenues for future research are discussed.

Delay discounting, time perspective, and self-schemas in adolescent alcohol drinking and disordered eating behaviors.

Delay discounting, time perspective, and self-schemas are well-known predictors of health risk behaviors among adolescents. However, the associations between these constructs and their influence on such behaviors are yet to be examined. This study aimed to determine the relationships among three cognitive constructs, namely, delay discounting, time perspective, and self-schemas, and determine the associations of these constructs with alcohol drinking (alcohol use and alcohol problems) and disordered eating behaviors in adolescents. Participants were 436 eighth-graders from three public junior high schools in southern Taiwan, who answered an anonymous questionnaire assessing self-schema, delay discounting, time perspective, and health risk behaviors. Generalized linear models with robust estimation were performed to estimate the effects; gender was the covariate. Delay discounting was associated with alcohol use (OR = 1.15), but not alcohol problems and disordered eating behaviors. Present-Hedonistic time perspective was associated with alcohol use (OR = 2.01), alcohol problems (IRR = 2.23), and disordered eating behaviors (Exp(b) = 1.38); while Future time perspective was associated with alcohol problems (IRR = 2.18). Drinker self-schema was associated with alcohol use (OR = 1.62) and alcohol problems (IRR = 1.71). Fat/overweight self-schema was associated with overall disordered eating (Exp(b) = 1.03). Thus, the findings suggest that each of the three constructs is independently associated with drinking and disordered eating behaviors, and these associations vary according to the specific type of behavior. Future research identifying the underlying mechanisms linking these constructs to the abovementioned behaviors can be useful for developing targeted intervention strategies.

A long time ago in a galaxy far, far away: How temporal are episodic contents?

A prominent feature of mental event (i.e. 'episodic') simulations is their temporal orientation: human adults can generate episodic representations directed towards the past or the future. Here, we investigated how the temporal orientation of imagined events relates to the contents of these events. Is there something intrinsically temporal about episodic contents? Or does their temporality rely on a distinct set of representations? In three experiments (N = 360), we asked participants to generate and later recall a series of imagined events differing in (1) location, (2) time of day, (3) temporal orientation, and (4) weekday. We then tested to what extent successful recall of episodic content (i.e. (1) and (2)) would predict recall of temporality and/or weekday information. Results showed that recall of temporal orientation was only weakly predicted by recall of episodic contents. Nonetheless, temporal orientation was more strongly predicted by content recall than weekday recall. This finding suggests that episodic simulations are unlikely to be intrinsically temporal in nature. Instead, similar to other forms of temporal information, temporal orientation might be determined from such contents by reconstructive post-retrieval processes. These results have implications for how the human ability to 'mentally travel' in time is cognitively implemented.

The role of inhibitory control and ADHD symptoms in the occurrence of involuntary thoughts about the past and future: An individual differences study.

In everyday life, people often experience involuntary thoughts about their personal past and future events in response to incidental cues in the environment. Yet, despite the abundance of such cues, our consciousness is not constantly flooded by these involuntary autobiographical memories (IAMs) and involuntary future thoughts (IFTs). The main goal of the present study was to further investigate the possibility that cognitive inhibitory control keeps these involuntary cognitions at bay. To test this inhibition hypothesis, we conducted a large-scale study (n = 157) in which groups of participants with different levels of inhibitory control (low, medium, high) and individuals with ADHD spectrum symptoms were engaged in a laboratory vigilance task in which the frequency of IFTs and IAMs was assessed. Contrary to predictions, although participants across groups differed significantly in terms of their individual inhibitory control capacity, the number of IFTs and IAMs reported during the vigilance task was comparable. In addition, individuals with the ADHD spectrum symptoms did not report more spontaneous thoughts compared to other groups. Together, these findings lend little support for the idea that inhibition is a key mechanism that regulates the occurrence of IAMs and IFTs in everyday life. Other possible mechanisms and avenues for future research are discussed.

The stability of visual perspective and vividness during mental time travel.

When remembering or imagining, people can experience an event from their own eyes, or as an outside observer, with differing levels of vividness. The perspective from, and vividness with, which a person remembers or imagines has been related to numerous individual difference characteristics. These findings require that phenomenology during mental time travel be trait-like-that people consistently experience similar perspectives and levels of vividness. This assumption remains untested. Across two studies (combined N = 295), we examined the stability of visual perspective and vividness across multiple trials and timepoints. Perspective and vividness showed weak within-session stability when reported across just a few trials but showed strong within-session stability when sufficient trials were collected. Importantly, both visual perspective and vividness demonstrated good-to-excellent across-session stability across different delay intervals (two days to six weeks). Overall, our results suggest that people dependably experience similar visual phenomenology across occurrences of mental time travel.

Manipulating the temporal locus and content of mind-wandering.

The human brain has a tendency to drift into the realm of internally-generated thoughts that are unbound by space and time. The term mind-wandering (MW) is often used describe such thoughts when they are perceptually decoupled. Evidence suggests that exposure to forward and backward illusory motion skews the temporal orientation of MW thoughts to either the future or past respectively. However, little is known about the impact of this manipulation on other features of MW. Here, using a novel experimental paradigm, we first confirmed that our illusory motion method facilitated the generation of MW thoughts congruent with the direction of motion. We then conducted content analyses which revealed that goal orientation and temporal distance were also significantly affected by the direction of illusory motion. We conclude that illusory motion may be an effective means of assaying MW and could help to elucidate this ubiquitous, and likely critical, component of cognition.

Inducing positive involuntary mental imagery in everyday life: an experimental investigation.

Positive involuntary mental imagery occurs frequently in daily life but evidence as to its functions and importance is largely indirect. The current study investigated a method to induce positive involuntary imagery in daily life, which would allow direct testing of its impact. An unselected student sample (N = 80) completed a single session of a positive imagery cognitive bias modification (CBM) paradigm, which involved listening to and imagining brief positive imagery scripts. Participants then recorded any involuntary memories of the imagined training scenarios in a three-day diary before returning to the lab for a follow-up assessment. Participants were randomised to imagine the scenarios in either an emotionally involved or emotionally detached manner, providing a test of the role of emotion in the subsequent experience of involuntary memories. Participants reported experiencing involuntary memories of the training scenarios in their daily life, but the number recorded did not differ between the experimental conditions. Exploratory analyses suggested that more vivid imagery and recall testing were associated with a greater number of involuntary memories. The study highlights the potential of the imagery CBM paradigm to further our understanding of the functions and potential importance of positive involuntary mental imagery in daily life.

Projecting the self in aging: an exploratory study of self-defining future projections.

The concept of "Self-Defining Future Projections" (SDFPs) has been recently introduced to better explore the link between future thinking and identity. To date, SDFPs have only been examined in young adults and it remains unknown how self-defining future thoughts evolve in aging. In this cross-sectional study, 43 young adults (age range = 19-28; mean age = 23.06) and 43 older adults (age range 60-80; mean age = 69.46) were asked to generate three SDFPs. Our results indicated that SDFPs were less specific in older adults compared to young adults, but there was no difference between the two groups concerning autobiographical reasoning. However, regarding subjective experience, older adults rated imagined future events as containing more sensory details and contextual information and reported a higher feeling of pre-experiencing the personal future. Additionally, older participants described future events that were more positive and less distant in the future, with fewer narratives about future achievements but more narratives describing leisure time, with a similar probability between the two groups that the event will occur in the future. Our study extends previous aging research and adds to the literature by better understanding how future event representations are formed in older adults.

Distance- rather than location-based temporal judgments are more accurate during episodic recall in a real-world task.

Definitions of episodic memory typically emphasise the importance of spatiotemporal frameworks in the contextual reconstruction of episodic retrieval. However, our ability to retrieve specific temporal contexts of experienced episodes is poor. This has bearing on the prominence of temporal context in the definition and evaluation of episodic memory, particularly among non-human animals. Studies demonstrating that rats rely on elapsed time (distance) rather than specific timestamps (location) to disambiguate events have been used to suggest that human episodic memory is qualitatively different to other species. We examined whether humans were more accurate using a distance- or location-based method for judging when an event happened. Participants (n = 57) were exposed to a series of events and then asked either when (e.g., 1:03 pm) or how long ago (HLA; e.g., 33 min) a specific event took place. HLA judgements were significantly more accurate, particularly for the most recently experienced episode. Additionally, a significantly higher proportion of participants making HLA judgements accurately recalled non-temporal episodic features across all episodes. Finally, for participants given the choice of methods for making temporal judgements, a significantly higher proportion chose to use HLA judgements. These findings suggest that human and non-human temporal judgements are not qualitatively different.

Preparation for certain and uncertain future outcomes in young children and three species of monkey.

This study examined 3-year old children and monkeys' capacities to prepare for immediate future events. In Study 1, children were presented with several tube apparatuses with two exits. When targets were certain to emerge from both, children tended to prepare to catch them by covering each exit. When it was uncertain where targets would emerge, however, they tended to prepare for only one possibility. These results substantiate the claim that simultaneous preparation for mutually exclusive possibilities develops relatively late. Study 2 found no evidence for such a capacity in monkeys (Ateles geoffroyi, Cebus apella, Papio hamadryas) given the same tasks.

"What has been is what will be"? Autobiographical memory and prediction of future events in depression.

Depression is associated with negative autobiographical thinking regarding the past and the future. The association between the two temporal dimensions, however, has not been examined. In the present study, 32 participants diagnosed with Major Depressive Disorder (MDD) and 32 controls completed a cued-recall task. Participants rated memories for positivity, frequency of occurrence to themselves/others, and expected recurrence, and listed planned social events and expected participation and enjoyment of these events. Memories of individuals diagnosed with MDD (vs. controls) were rated as more negative by both participants and objective coders. Individuals diagnosed with MDD were more negative in their evaluation of past events and in future expectations compared to controls. For both groups, expected recurrence of positive past events was associated with the frequency of these events occurring to oneself. For individuals diagnosed with MDD, however, expected recurrence of negative past events was associated exclusively with the frequency of these events occurring to self and not to others. Expectations for past events' recurrence predicted increased expected participation and enjoyment from social events in both groups. These results suggest that memory in MDD is associated with more negative future expectations, which may affect mood and motivation.

Anticipated nostalgia: Looking forward to looking back.

Anticipated nostalgia is a new construct that has received limited empirical attention. It concerns the anticipation of having nostalgic feelings for one's present and future experiences. In three studies, we assessed its prevalence, content, emotional profile, and implications for self-regulation and psychological functioning. Study 1 revealed that anticipated nostalgia most typically concerns interpersonal relationships, and also concerns goals, plans, current life, and culture. Further, it is affectively laden with happiness, sadness, bittersweetness, and sociality. Studies 2 and 3 assessed the implications of anticipated nostalgia for self-regulation and psychological functioning. In both studies, positive evaluation of a personal experience was linked to stronger anticipated nostalgia, and anticipated nostalgia was linked to savouring of the experience. In Study 3, anticipated nostalgia measured prior to an important life transition predicted nostalgia a few months after the transition, and post-transition nostalgia predicted heightened self-esteem, social connectedness, and meaning in life.

Mind-Wandering in People with Hippocampal Damage.

Subjective inner experiences, such as mind-wandering, represent the fundaments of human cognition. Although the precise function of mind-wandering is still debated, it is increasingly acknowledged to have influence across cognition on processes such as future planning, creative thinking, and problem-solving and even on depressive rumination and other mental health disorders. Recently, there has been important progress in characterizing mind-wandering and identifying the associated neural networks. Two prominent features of mind-wandering are mental time travel and visuospatial imagery, which are often linked with the hippocampus. People with selective bilateral hippocampal damage cannot vividly recall events from their past, envision their future, or imagine fictitious scenes. This raises the question of whether the hippocampus plays a causal role in mind-wandering and, if so, in what way. Leveraging a unique opportunity to shadow people (all males) with bilateral hippocampal damage for several days, we examined, for the first time, what they thought about spontaneously, without direct task demands. We found that they engaged in as much mind-wandering as control participants. However, whereas controls thought about the past, present, and future, imagining vivid visual scenes, hippocampal damage resulted in thoughts primarily about the present comprising verbally mediated semantic knowledge. These findings expose the hippocampus as a key pillar in the neural architecture of mind-wandering and also reveal its impact beyond episodic memory, placing it at the heart of our mental life.SIGNIFICANCE STATEMENT Humans tend to mind-wander ∼30-50% of their waking time. Two prominent features of this pervasive form of thought are mental time travel and visuospatial imagery, which are often associated with the hippocampus. To examine whether the hippocampus plays a causal role in mind-wandering, we examined the frequency and phenomenology of mind-wandering in patients with selective bilateral hippocampal damage. We found that they engaged in as much mind-wandering as controls. However, hippocampal damage changed the form and content of mind-wandering from flexible, episodic, and scene based to abstract, semanticized, and verbal. These findings expose the hippocampus as a key pillar in the neural architecture of mind-wandering and reveal its impact beyond episodic memory, placing it at the heart of our mental life.

Spontaneous cognition in dysphoria: reduced positive bias in imagining the future.

Anomalies in future-oriented cognition are implicated in the maintenance of emotional disturbance within cognitive models of depression. Thinking about the future can involve mental imagery or verbal-linguistic mental representations. Research suggests that future thinking involving imagery representations may disproportionately impact on-going emotional experience in daily life relative to future thinking not involving imagery (verbal-linguistic representation only). However, while higher depression symptoms (dysphoria) are associated with impaired ability to deliberately generate positive relatively to negative imagery representations of the future (when instructed to do so), it is unclear whether dysphoria is associated with impairments in the tendency to do so spontaneously (when not instructed to deliberately generate task unrelated cognition of any kind). The present study investigated dysphoria-linked individual differences in the tendency to experience spontaneous future-oriented cognition as a function of emotional valence and representational format. Individuals varying in dysphoria level reported the occurrence of task unrelated thoughts (TUTs) in real time while completing a sustained attention go/no-go task, during exposure to auditory cues. Results indicate higher levels of dysphoria were associated with lower levels of positive bias in the number of imagery-based future TUTs reported, reflecting higher negative imagery-based future TUT generation (medium to large effect size), and lower positive imagery-based TUT generation (small to medium effect size). Further, this dysphoria-linked bias appeared to be specific in temporal orientation (future, not past) and representational format (imagery, not non-imagery). Reduced tendency to engage in positive relative to negative imagery-based future thinking appears to be implicated in dysphoria.