A LORETA study of mental time travel: Similar and distinct electrophysiological correlates of re-experiencing past events and pre-experiencing future events

Previous studies exploring mental time travel paradigms with functional neuroimaging techniques have uncovered both common and distinct neural correlates of re-experiencing past events or pre-experiencing future events. A gap in the mental time travel literature exists, as paradigms have not explored the affective component of re-experiencing past episodic events; this study explored this sparsely researched area. The present study employed standardized low resolution electromagnetic tomography (sLORETA) to identify electrophysiological correlates of re-experience affect-laden and non-affective past events, as well as pre-experiencing a future anticipated event. Our results confirm previous research and are also novel in that we illustrate common and distinct electrophysiological correlates of re-experiencing affective episodic events. Furthermore, research from this experiment yields results outlining a pattern of activation in the frontal and temporal regions is correlated with the time frame of past or future events subjects imagined.     

Travelling backwards and forwards in time: culture and gender in the episodic specificity of past and future events

There is considerable evidence that, when recalling past events, Westerners exhibit greater episodic specificity than East Asians and women exhibit greater episodic specificity than men. Yet it is unknown whether the same cultural and gender differences are true for future events. In the present study 209 European American and Chinese young adults were asked to recall past personal events and imagine future personal events occurring in varied time periods (i.e., 1 week, 1 year, 10-15 years). Regardless of time period, European Americans consistently produced more specific details than Chinese for future events than they did for past events, and women produced more specific details than men for both past and future events. These findings provide additional support for the constructive-episodic-simulation hypothesis, and shed new light on the influence of culture and gender on episodic thinking.     

Experiencing past and future personal events: functional neuroimaging evidence on the neural bases of mental time travel

Functional MRI was used in healthy subjects to investigate the existence of common neural structures supporting re-experiencing the past and pre-experiencing the future. Past and future events evocation appears to involve highly similar patterns of brain activation including, in particular, the medial prefrontal cortex, posterior regions and the medial temporal lobes. This result seems to support the view of a common neurocognitive system, which would allow humans to mentally travel through time. Past events recollection was associated with greater amplitude of hippocampal and anterior medial prefrontal hemodynamic responses. This result is discussed in terms of the involvement of the self in the conscious experience of past and future events representations. More generally, our data provide new evidence in favour of the idea that re- and pre-experiencing past and future events may rely on similar cognitive capacities.     

Reconstructing the times of past and future personal events

Humans have the remarkable ability to mentally travel through past and future times. However, while memory for the times of past events has been much investigated, little is known about how imagined future events are temporally located. Using a think-aloud protocol, we found that the temporal location of past and future events is rarely directly accessed, but instead mostly relies on reconstructive and inferential strategies. References to lifetime periods and factual knowledge (about the self, others, and the world) were most frequently used to determine the temporal location of both past and future events. Event details (e.g., places, persons, or weather conditions) were also used, but mainly for past events. Finally, the results showed that events whose temporal location was directly accessed were judged more important for personal goals. Together, these findings shed new light on the mechanisms involved in locating personal events in past and future times.     

Children's temporal judgments for autobiographical past and future events

We compared the performance of twenty 5-7-year-olds on two spatial-temporal judgment tasks. In a semantic task, children located temporal distances from today that were described using conventional, temporal terms on a spatial timeline. In an autobiographical task, children judged temporal distances on the same spatial timeline for events that they had experienced, or were going to experience, presented without explicit temporal references. Six-year-olds were equally accurate in judging temporal distances in the semantic and autobiographical tasks, but 7-year-olds were more accurate in the semantic task. Older children were more accurate than younger children in the semantic task, but no significant age differences were found for autobiographical events. Surprisingly, children were equally accurate in locating past and future events in time. Children at both ages were more accurate judging temporal distances up to one week away (both past and future) as compared to distances of two to four weeks across both tasks. Results suggest that knowledge of recurring time patterns and conventional time measurement systems is necessary, but not sufficient, for locating autobiographical events in time, and temporal distance plays an important role in children's temporal judgments.     

The role of cognitive resources in the valuation of near and far future events

People's behaviors often appear short-sighted, suggesting they overvalue the near future and undervalue the far future. In three experiments, the present research focussed on the role of cognitive resources in the valuation of near and distant future events. Experiment 1 tested a new discounting paradigm for use in the subsequent experiments. Experiments 2 and 3 used different manipulations (time pressure and a concurrent tone task) to restrict the cognitive resources of participants valuing a series of future events. In both experiments, this manipulation caused an increase in the valuation of far future events but not in the valuations of near future events. Implications of these findings for the role of cognitive resources in time discounting processes are briefly discussed.     

Children's reasoning about the temporal order of past and future events

Four- and five-year-olds completed two sets of tasks that involved reasoning about the temporal order in which events had occurred in the past or were to occur in the future. Four-year-olds succeeded on the tasks that involved reasoning about the order of past events but not those that involved reasoning about the order of future events, whereas 5-year-olds passed both types of tasks. Individual children who failed the past-event tasks were not particularly likely to fail the more difficult future-event tasks. However, children's performance on the reasoning tasks was predictive of their performance on a task assessing their comprehension of the terms “before” and “after.” Our results suggest that there may be a developmental change over this age range in the ability to flexibly represent and reason about the before-and-after relationships between events.     

Separating past and future autobiographical events in memory: Evidence for a reality monitoring asymmetry

After thinking about the past and imagining the future, how do people separate these real and imagined events in memory? We had subjects engage in past and future autobiographical elaboration, then later take memory tests that required them to recollect these earlier generated events. In Experiment 1, testing memory for previously generated past or future autobiographical events led to fewer source memory confusions than did an elaborative control task, suggesting that the distinctive features of autobiographical elaboration improved subsequent retrieval monitoring accuracy. In Experiment 2, we directly compared retrieval monitoring accuracy for previously generated past and future autobiographical events and found that subjects made fewer source confusions when searching memory for future events. This asymmetry suggests that the features characterizing future elaborations (e.g., cognitive operations) were used more effectively during reality monitoring than were the features characterizing past elaborations (e.g., perceptual details), and has implications for future-oriented theories of memory.     

The temporal distribution of past and future autobiographical events across the lifespan

Knowledge and awareness of past and future autobiographical events may be mediated by a common system that supports intentional, goal-directed behavior. The purpose of this study was to assess the correspondence of past and future autobiographical thought. In Experiment 1, 300 undergraduates aged 19 years generated and assigned dates to past and f utu re autobiographical events. Thetemporal distribution of past events replicated a power function for retention as has been described in past research. The intention function of future autobiographical events fit the inverse of this same power function, reflecting a temporality of past and future mental time travel centered around the present moment. In Experiment 2, these findings were extended to young, middle-aged, and older groups. These data provide empirical support for the notion that thinking outside of "now" is mediated by a common system, regardless of whether one is thinking about the past or the future.     

Prospective memory for future intentions: Some comparisons with memory for past events

Abstract

Memory for future intentions was compared with memory for past activities by asking members of a film society to retrieve names of films they intended to see later on in a Season and films they had seen earlier. Memory for films that had been seen showed the usual recency effect, while retrieval of films to be seen showed an analogous proximity effect in that films to be seen sooner were more accessible. It was also found that recall of past films was inversely related to the total number of such films, but was unrelated to the average time interval since they were seen. In a similar fashion, retrievability of future films was inversely related to the total number of such films and was unrelated to when they were to be seen. There was a small but significant correlation between an individual's ability to retrieve the names of past and future films. Taken together, these correspondences suggest that similar empirical laws may govern the retrieval of stored information about past events and future intentions. Possible interpretations of the proximity effect and its theoretical implications are discussed.     

The reality of the past versus the ideality of the future: emotional valence and functional differences between past and future mental time travel

Mental time travel (MTT) is the ability to mentally project oneself backward or forward in time in order to remember an event from one’s personal past or to imagine a possible event in one’s personal future. Past and future MTT share many similarities, and there is evidence to suggest that the two temporal directions rely on a shared neural network and similar cognitive structures. At the same time, one major difference between past and future MTT is that future as compared to past events generally are more emotionally positive and idyllic, suggesting that the two types of event representations may also serve different functions for emotion, self, and behavioral regulation. Here, we asked 158 participants to remember one positive and one negative event from their personal past as well as to imagine one positive and one negative event from their potential personal future and to rate the events on phenomenological characteristics. We replicated previous work regarding similarities between past and future MTT. We also found that positive events were more phenomenologically vivid than negative events. However, across most variables, we consistently found an increased effect of emotional valence for future as compared to past MTT, showing that the differences between positive and negative events were larger for future than for past events. Our findings support the idea that future MTT is biased by uncorrected positive illusions, whereas past MTT is constrained by the reality of things that have actually happened.     

Collective mental time travel: remembering the past and imagining the future together

Synthese - Bringing research on collective memory together with research on episodic future thought, Szpunar and Szpunar (Mem Stud 9(4):376–389, 2016) have recently developed the concept of...     

Emotional reaction to past and future events as a function of temporal distance

In three experiments with 30 Ss, imagined past and future events were used as stimuli. Scales were constructed by the ratio estimation method for (a) subjective temporal distance and (b) emotional reaction to the events. It was found (1) that subjective temporal distance was a power function of chronological distance, (2) that emotional reaction to past events could be described as an exponential function of subjective temporal distance; a simple relation thus exists between the two psychological variables, whereas emotional reaction is related in a more complicated way to the objective variable, and (3) that emotional reaction to future events could be described about as well by a power function as by an exponential function of both subjective and objective temporal distance.     

With the past behind and the future ahead: Back-to-front representation of past and future sentences

Several studies support the psychological reality of a mental timeline that runs from the left to the right and may strongly affect our thinking about time. Ulrich and Maienborn (Cognition 117:126–138, 2010) examined the linguistic relevance of this timeline during the processing of past- and future-related sentences. Their results indicate that the timeline is not activated automatically during sentence comprehension. While no explicit reference of temporal expressions to the left–right axis has been attested (e.g., *the meeting was moved to the left), natural languages refer to the back–front axis in order to encode temporal information (e.g., the meeting was moved forward). Therefore, the present study examines whether a back–frontal timeline becomes automatically activated during the processing of past- and future-related sentences. The results demonstrate a clear effect on reaction time that emerges from a time–space association along the frontal timeline (Experiment 1). However, this activation seems to be nonautomatic (Experiment 2), rendering it unlikely that this frontal timeline is involved in comprehension of the temporal content of sentences.     

A matter of time: actual time and the production of the past

In psychoanalytic theory, space metaphors are frequently used to describe the psychic apparatus. As for time, it is traditionally invoked under the heading of timelessness of the unconscious, more aptly described as the resistance of the repressed to wearing away with time. This paper examines how the insertion of time into psychic events and structural differentiation form a single process. After looking into the parallelism between phenomenological and psychoanalytic views of time and differentiation, the author draws a distinction between two time categories: chronological versus actual. A clinical example is presented.     

Mental time travel into the episodic future,episodic past,and episodic counterfactual past in everyday life

To date, studies exploring the relationship of counterfactual thoughts with episodic memories and episodic future thoughts have focused mainly on voluntary mental time travel. We explore mental time travel in everyday life and find that episodic counterfactual thinking occurs to a much lesser extent than thinking about the past or the future (12%, 22%, and 54%, respectively), is used mainly for mood regulation purposes, and the temporal distribution decreases as a function of time. We observe similarities in phenomenological detail: memories and counterfactual thoughts sharing similar ratings of sensory detail, memories and future thoughts sharing similar ratings of positivity, and counterfactual and future thoughts sharing similar ratings of mental time travel. We discuss the implications of episodic counterfactual thinking in everyday life.