Xiaoqing Hu

Human memory recall is flexible in time, allowing past events to be mentally replayed at variable speeds. However, it remains unclear whether temporally rescaled replay distorts the perceived duration of remembered events, and whether such distortion is tied to changes in the retrieved content. Here we instructed participants to mentally replay previously encoded naturalistic videos at compressed, expanded, or self-paced (free) speeds while recording scalp electroencephalography (EEG). Replaying an event at an expanded pace lengthened participants' subsequent judgments of its original duration relative to free and compressed replay, and the longer an event had been replayed, the longer it was judged to have lasted. Crucially, recalled memory content was unaffected, with gist accuracy and recalled detail comparable across speed conditions. During replay, alpha and theta power were reduced under compression, and both interacted with the speed instruction in predicting reported duration. Specifically, alpha power exhibited a stronger positive relationship with duration judgments under compressed replay than under free or expanded replay. Conversely, the relationship between theta power and reported duration was significantly more positive under expanded replay than under free or compressed replay. Neural pattern similarity between instructed and later spontaneous replay varied with replay speed, yet this reinstatement neither predicted reported duration nor mediated the oscillatory effects. These findings suggest that remembered duration is not read out from the amount of content retrieved but reconstructed at retrieval through oscillatory dynamics, decoupling the subjective scaling of time from the content of memory.

Episodic memory provides a temporal scaffold that organizes past experiences according to their sequential occurrence. While memories are reactivated and consolidated during sleep, it remains unknown how exogenous reactivation reshapes memories of complex events—particularly the temporal structure that binds individual elements across time. In this preregistered study, 35 participants encoded neutral and aversive narratives composed of image sequences, with auditory context shifts defining event boundaries. During post-encoding slow-wave sleep, closed-loop targeted memory reactivation (TMR) delivered boundary-associated auditory cues time-locked to the up-state of slow oscillations. Reactivation led to faster, more confident, and more liberal recognition responses for cued than uncued memories. However, reactivation exerted a time-dependent effect on temporal-order memory, impairing it immediately after sleep but attenuating forgetting one week later. This behavioral dissociation was paralleled at the neural level: stronger cue-elicited theta activity predicted superior recognition of neutral—but not aversive—event content, whereas greater theta responses were associated with poorer temporal-order memory for the same events. Together, these findings suggest that sleep reactivation does not uniformly strengthen episodic memories. Rather, it selectively prioritizes access to event content while reorganizing temporal relations among event elements, revealing distinct, time-dependent consequences of sleep reactivation for different components of complex experiences.

Sleep is critical for memory consolidation and emotional regulation, yet the respective roles of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep remain unclear. Here, using a within-subject crossover design, we recorded high-density electroencephalography (EEG) across two experimental nights while participants viewed neutral or aversive film clips in a counterbalanced order. Combining with daytime functional localizers establishing neural patterns of aversive vs. neutral emotional processing, multivariate pattern analysis revealed that the reactivation of aversive vs. neutral memory during nocturnal sleep was both stage-dependent and event-specific. In NREM sleep, valence-specific reactivation was time-locked to slow oscillation (SO)-spindle complexes but not to either event alone; in REM sleep, reactivation occurred selectively during phasic REM periods marked by rapid eye movements. Critically, NREM SO-spindle coupling percentage was associated with consolidation of temporal memories; whereas phasic REM reactivation strength was linked to overnight dissipation of negative affect. Our findings provide direct evidence that sleep reprocesses emotional experiences through dissociable stage- and event-specific mechanisms, laying out a framework for future targeted sleep-based interventions.

Summary: Positive self-evaluation underpins resilience and mental health, yet how to enhance positive self-evaluation and the underlying neurocognitive mechanisms remain poorly understood. Existing data mostly examined self-evaluative processing of the wakeful minds, with the role of sleep remain unexplored. Here, we demonstrated that reactivation of positive self-evaluation during sleep revealed fine-grained neural-evaluative alignment that varies with depressive symptoms. We found that targeted reactivation of positive personality traits during non-rapid eye movement (NREM) sleep enhanced positive self-evaluation, but this benefit diminished with elevated depressive symptoms. Moreover, cueing positive traits during NREM sleep elicited trait-specific, 11-16 Hz EEG sigma power-based neural representations that aligned with post-sleep positive self-evaluative representational structures, as revealed by representational similarity analyses. Notably, individuals with elevated depressive symptoms exhibited weaker neural-evaluative representational alignments, identifying a maladaptive self-evaluative processing that bridges across sleep and wakefulness states. These findings provide mechanistic insights on how fine-grained neural-evaluative alignment can substantiate positive self-evaluation, and why it was disrupted as depressive symptoms increased. Highlights: Positive-trait reactivation during NREM sleep enhances positive self-evaluation This behavioral benefit decreases as depressive symptoms increase Sleep cueing evokes trait-specific sigma-band neural representations Neural–evaluative alignment weakens as depressive symptoms increase

Study Objectives: To develop and initially validate the Circadian Disruption Index (CDI), a self-report measure of circadian disruption, and obtain preliminary evidence of its responsiveness to circadian health education. Methods: In Study 1, 244 participants completed a 22-item CDI version and external measures. The sample was randomly divided for exploratory and confirmatory factor analyses. Internal consistency, external associations, and discrimination of poor sleep quality were examined. In Study 2, 72 postgraduate students completed the CDI before and 1 week after a 16-hour circadian health education program in an uncontrolled pre-post design. Results: Analyses yielded a 15-item, three-factor structure comprising rhythm stability and light exposure, behavioral habits and diet, and sleep quality and subjective complaints. Total-score internal consistency was acceptable (Cronbach’s α = 0.871). Confirmatory factor analysis showed a comparative fit index of 0.902 and a root mean square error of approximation of 0.072, although the Tucker-Lewis index was 0.882. CDI scores correlated with sleep quality, chronotype, corrected midsleep on free days, depression, and anxiety, but not social jetlag. The area under the curve for poor sleep quality was 0.807 (95% confidence interval, 0.753-0.862), with an exploratory cutoff of ≥ 23. In Study 2, CDI scores decreased from 22.26 to 19.88 ( p = 0.002; Cohen’s d _z = 0.36). Conclusions: The CDI demonstrated satisfactory internal consistency, a meaningful multidimensional structure, and responsiveness to short-term changes following circadian health education, supporting its potential utility for assessing circadian disruption and monitoring circadian-related behavioral changes. Statement of Significance: Existing questionnaires typically assess isolated aspects of circadian functioning, such as chronotype, sleep timing, or sleep quality, leaving a need for a brief measure that captures the broader burden of circadian disruption. This study introduces the Circadian Disruption Index, which integrates rhythm stability and light exposure, behavioral habits and diet, and sleep-related complaints within a single self-report instrument. Initial findings support its multidimensional structure and short-term responsiveness following circadian health education. The index may provide a practical tool for population research and the evaluation of circadian-focused interventions.

Memory cues can be associated with both positive and negative experiences at different time points, in either a positive-to-negative or negative-to-positive order. While sleep preferentially consolidates recent experiences, its impact on emotional memory across such opposing-valence sequences remains unclear. We tested whether sleep differentially modulates delayed cue affect in positive-to-negative versus negative-to-positive conditions. One hundred twenty participants were randomly assigned to sleep or wake groups and completed both conditions in counterbalanced order. Participants learned pseudoword-picture associations where the same cues were paired with emotional pictures of opposite valence. Emotional valence ratings were collected immediately after encoding and after a 12 h interval (overnight sleep vs. daytime wakefulness). Sleep led to more positive cue ratings in the negative-to-positive condition and more negative ratings in the positive-to-negative condition, compared to wake controls. Stronger positive picture ratings predicted greater positive-valence shifts after sleep in the negative-to-positive condition. These findings indicate that sleep preferentially modulates the affective tone of memories encoded closer to sleep onset, independent of recognition accuracy. This suggests a dissociation between mnemonic and affective consolidation, where sleep selectively biases emotional value according to the temporal order of experience. This principle may inform therapeutic strategies for optimizing emotional outcomes by timing positive experiences before sleep, though clinical applications require further study.

Memory guides everyday evaluations and decision-making. Yet people often encounter inconsistent information about the same target, giving rise to conflicting evaluative memories and decision ambivalence. Decision ambivalence is not only aversive but also reduces confidence, increases hesitation, and leads to maladaptive choices. While sleep consolidates memories, its role in resolving these evaluative conflicts and shaping decision dynamics remains unknown. Here, we investigated how memory reactivation during sleep, a critical period for memory consolidation and transformation, would reconstruct conflicting evaluative memories and thus influence next-day decision ambivalence. In a valence reversal learning procedure, participants first encoded positive or negative cue-outcome associations (A-B) on Day 1, followed by learning A-C associations yet with opposite valences on Day 2 (i.e., Day 1 negative-to-Day 2 positive and Day 1 positive-to-Day 2 negative). During subsequent non-rapid eye movement (NREM) sleep on Day 2 night, half of the cues were re-presented to sleeping participants to reactivate the cue-associated memories. Upon waking up, participants completed post-sleep evaluation and memory tests. Our results showed that cueing reduced decision ambivalence, especially in the negative-to-positive condition, as evidenced by less curved mouse-tracking trajectories. Meanwhile, cueing promoted the integration of conflicting evaluative memories, again in the negative-to-positive condition. Critically, cueing-induced ambivalence reduction was evident only for items that were integrated after sleep. Electrophysiologically, stronger cue-elicited delta power during NREM sleep predicted next-day ambivalence reduction, while higher cue-elicited spindle probabilities were associated with better memory integration. Together, our findings suggest that memory reactivation during post-learning NREM sleep actively reorganizes conflicting memories, providing a mechanistic pathway through which offline memory reprocessing resolves waking decision ambivalence.

Background: Insomnia disorder is a common sleep disturbance characterized by adverse daytime cognitive and emotional impairments, such as repetitive negative thinking and increased psychological distress. Memory control, a key self-regulatory ability to control or inhibit unwanted thoughts and memories, plays an essential role in supporting cognitive functions and emotional well-being. Here, we delineate the neurocognitive mechanisms underlying memory control among individuals with insomnia. Methods: 41 participants meeting DSM-5 criteria for insomnia disorder and 40 healthy sleepers completed an emotional Think/No-Think task, during which participants either retrieved (Think) or suppressed the retrieval (No-Think) of aversive memories in response to memory cues while electroencephalograms were recorded. Results: Linear mixed model analyses with age and depression scores as covariates showed that participants with insomnia exhibited impaired memory control abilities, as evidenced by reduced suppression-induced forgetting in memory recall when compared to healthy sleepers. Electrophysiologically, healthy sleepers showed enhanced right prefrontal theta power in retrieval suppression than in retrieval, indicating elevated needs of inhibitory control during memory control. In sharp contrast, this difference was absent among those with insomnia. Notably, the greater the severity of insomnia symptoms, the smaller the retrieval vs. retrieval suppression theta power differences across participants, linking inefficient top-down control of unwanted memories with low sleep qualities. Conclusion: Individuals with insomnia showed impaired memory control of aversive memories and aberrant electrophysiological activities during retrieval suppression. Future research shall investigate the causal relationship between memory control abilities and insomnia symptoms.

Sleep has traditionally been conceptualized as a state of cognitive disconnection, yet emerging evidence indicates that decision-making capacities persist across sleep stages. Here, we elucidate the computational mechanisms underlying real-time lexical decision-making during polysomnographically-verified sleep, using facial electromyography and hierarchical drift diffusion modeling in both healthy individuals and participants with narcolepsy. We found that lexical decision-making was preserved during N1 and lucid REM sleep, but relied on distinct computational strategies: in N1 sleep, both enhanced sensory-motor processing and increased evidence accumulation supported decisions about words, whereas in lucid REM sleep, lexical decisions were driven exclusively by evidence accumulation processes. Cross-state comparisons revealed two fundamental principles: (1) Selective preservation—during N1 sleep, lexical decisions for words were maintained while those for pseudowords were selectively impaired, indicating that cognitive resources during sleep are preferentially allocated to meaningful stimuli; (2) Parallel strategic adaptations—during lucid REM sleep, participants increased their decision thresholds, requiring more evidence before responding, which helped maintain accuracy even though the efficiency of evidence accumulation was reduced. Our findings demonstrate that, rather than a passive decline, sleep involves dynamic and state-specific reconfiguration of the computational mechanisms underlying decision-making, with important implications for understanding consciousness and cognitive flexibility.