The hippocampal-entorhinal region supports memory for episodic details, such as temporal relations of sequential events, and mnemonic constructions combining experiences for inferential reasoning. However, it is unclear whether hippocampal event memories reflect temporal relations derived from mnemonic constructions, event order, or elapsing time, and whether these sequence representations generalize temporal relations across similar sequences. Here, participants mnemonically constructed times of events from multiple sequences using infrequent cues and their experience of passing time. After learning, event representations in the anterior hippocampus reflected temporal relations based on constructed times. Temporal relations were generalized across sequences, revealing distinct representational formats for events from the same or different sequences. Structural knowledge about time patterns, abstracted from different sequences, biased the construction of specific event times. These findings demonstrate that mnemonic construction and the generalization of relational knowledge combine in the hippocampus, consistent with the simulation of scenarios from episodic details and structural knowledge.

Trauma memories can appear dissociated from their original temporal context, and are often relived as they occur in the here-and-now. Potentially these temporal distortions already occur during encoding of the aversive experience as a consequence of stress. Here, 86 participants were subjected to either a stress or control induction, after which they learned the temporal structure of four virtual days. In these virtual days, time was scaled and participants could use clock cues to construe the passage of time within a day. We examined whether stress causes a shift in the learning strategy from one based on virtual time to one based on event sequence. Our results do not show a discernible impact of stress on memory for temporal context, in terms of both sequence memory and more fine-grained representations of time. The stress groups showed more extreme performance trajectories, either good or poor, across all measures. However, as time estimations were overall quite poor it is unclear to what extent this reflected a true strategy shift. Future avenues of research that can build on these findings are discussed.

Negative thoughts about future events are a central aspect of anxiety disorders. It is important to gain a deeper understanding of how these imagined events are retained over time when considering the impact of negative future thoughts on anxiety. Prior research indicates that emotional intensity fades faster for negative than positive memories in healthy individuals. This so-called fading-affect bias could extend to recall of imagined future events. Furthermore, several studies have suggested that this bias may be reversed in individuals with high levels of anxiety. In the current study, we examined whether individuals with high anxiety ( n = 23), relative to individuals with low anxiety ( n = 30), showed faster decay for positive than negative future-event simulations. The results show that emotion facilitated cued recall for imagined future events in the low-anxiety group but not in the high-anxiety group. In addition, individuals with high anxiety showed decreased episodic specificity during recall across all emotional conditions.

The hippocampal-entorhinal region supports memory for episodic details, such as temporal relations of sequential events, and mnemonic constructions combining experiences for inferential reasoning. However, it is unclear whether hippocampal event representations reflect temporal relations derived from mnemonic constructions, event order, or elapsing time, and whether they generalize temporal relations across similar sequences. Here, participants mnemonically constructed times of events from multiple sequences using infrequent cues and their experience of passing time. After learning, event representations in the anterior hippocampus reflected sequence relations based on constructed times. These event representations generalized across sequences, revealing distinct representational formats for events from the same or different sequences. Structural knowledge about time patterns, abstracted from different sequences, biased the construction of specific event times. These findings demonstrate that the hippocampus reconciles representations of specific relations with the generalization across different episodes, consistent with memory-based constructions combining episodic details and general knowledge to simulate scenarios.

Expectations have an important role in guiding behavior and the interpretation of novel information, but can contain negative biases such as is the case in anxiety disorders. Positive future thinking may provide an accessible way to attenuate these negatively biases. However, much is still unclear about the optimal form of such positive interventions, and it is unknown if the effects go beyond subjective experience. Here, we used a positive future thinking intervention to adapt the way a stressful event is experienced. Participants imagined either task-relevant (N = 21) or irrelevant (N = 21) positive future events before being subjected to the Trier Social Stress Task, or did not receive the intervention (N= 20). We recorded resting state EEG during the anticipation and recovery phases of the TSST to assess intervention and trait anxiety related differences in the level of frontal delta-beta coupling, which is considered a neurobiological substrate of emotion regulation. Results show that the intervention reduces event-related stress and anxiety, and increases social fixation behavior and task performance, but only if future thinking is task relevant. Paradoxically, task-irrelevant positive future thoughts enhance negative perceptual biases and stress reactivity. This increase in stress reactivity in the task-irrelevant group was corroborated by the elevated levels frontal delta-beta coupling during event anticipation, especially for those with high trait anxiety. This suggests an increased demand for emotion regulation following the task-irrelevant intervention, possibly due to the contextual incongruence between positive imagery and the stressor. Together, these results show that positive future thinking can mitigate the negative emotional, behavioral and neurobiological consequences of a stressful event, but that it should not be applied indiscriminately. Task-relevant positive future thinking can be an accessible way to boost efficacy of exposure therapy for pathological anxiety, and can help people deal with negative anticipation in daily life.