Forgetting unwanted memories in sleep.

Memories are sometimes best forgotten, but how do our brains weaken unwanted details of the past? We propose a theoretical framework in which memory reactivation during sleep supports adaptive forgetting. This mnemonic rebalancing underpins the affective benefits of sleep by ensuring that our memories remain aligned with our emotional goals.

Sleep interventions for adults admitted to psychiatric inpatient settings: A systematic scoping review.

Sleep disturbances are common, affecting over half of adults with a mental disorder. For those admitted to a psychiatric ward, difficulties with sleep, particularly insomnia, are compounded by factors relating to the inpatient setting. We conducted a scoping review of sleep intervention studies involving adults admitted to psychiatric settings. We categorised the different types of sleep interventions and identified the effects on sleep and other mental and physical health outcomes. Instruments used to measure sleep were also examined. The search strategy yielded 4780 studies, of which 28 met the inclusion criteria. There was evidence of more non-pharmacological than pharmacological interventions having been tested in inpatient settings. Results indicated that non-pharmacological interventions based on cognitive behaviour therapy for insomnia improve sleep and may improve mental and physical health. Several distinct sleep measures were used in the studies. Gaps in the literature were identified, highlighting the importance of research into a wider range of sleep interventions tested against robust controls, using validated measures of sleep with evaluation of additional mental and physical health outcomes among a large sample size of adults in the psychiatric inpatient settings.

Delineating memory reactivation in sleep with verbal and non-verbal retrieval cues.

Sleep supports memory consolidation via the reactivation of newly formed memory traces. One way to investigate memory reactivation in sleep is by exposing the sleeping brain to auditory retrieval cues; a paradigm known as targeted memory reactivation. To what extent the acoustic properties of memory cues influence the effectiveness of targeted memory reactivation, however, has received limited attention. We addressed this question by exploring how verbal and non-verbal memory cues affect oscillatory activity linked to memory reactivation in sleep. Fifty-one healthy male adults learned to associate visual stimuli with spoken words (verbal cues) and environmental sounds (non-verbal cues). Subsets of the verbal and non-verbal memory cues were then replayed during sleep. The voice of the verbal cues was either matched or mismatched to learning. Memory cues (relative to unheard control cues) prompted an increase in theta/alpha and spindle power, which have been heavily implicated in sleep-associated memory processing. Moreover, verbal memory cues were associated with a stronger increase in spindle power than non-verbal memory cues. There were no significant differences between the matched and mismatched verbal cues. Our findings suggest that verbal memory cues may be most effective for triggering memory reactivation in sleep, as indicated by an amplified spindle response.

Neural reactivation during human sleep.

Sleep promotes memory consolidation: the process by which newly acquired memories are stabilised, strengthened, and integrated into long-term storage. Pioneering research in rodents has revealed that memory reactivation in sleep is a primary mechanism underpinning sleep's beneficial effect on memory. In this review, we consider evidence for memory reactivation processes occurring in human sleep. Converging lines of research support the view that memory reactivation occurs during human sleep, and is functionally relevant for consolidation. Electrophysiology studies have shown that memory reactivation is tightly coupled to the cardinal neural oscillations of non-rapid eye movement sleep, namely slow oscillation-spindle events. In addition, functional imaging studies have found that brain regions recruited during learning become reactivated during post-learning sleep. In sum, the current evidence paints a strong case for a mechanistic role of neural reactivation in promoting memory consolidation during human sleep.

Better late than never: sleep still supports memory consolidation after prolonged periods of wakefulness.

While the benefits of sleep for associative memory are well established, it is unclear whether single-item memories profit from overnight consolidation to the same extent. We addressed this question in a preregistered, online study and also investigated how the temporal proximity between learning and sleep influences overnight retention. Sleep relative to wakefulness improved retention of item and associative memories to similar extents irrespective of whether sleep occurred soon after learning or following a prolonged waking interval. Our findings highlight the far-reaching influences of sleep on memory that can arise even after substantial periods of wakefulness.

The influence of emotion regulation strategies and sleep quality on depression and anxiety.

Chronic stress is a major risk factor for a number of mental health disorders, including depression and pathological anxiety. Adaptive cognitive emotion regulation (CER) strategies (i.e. positively-focused thought processes) can help to prevent psychiatric disturbance when enduring unpleasant and stressful experiences, but little is known about the inter-individual factors that govern their success. Sleep plays an important role in mental health, and may moderate the effectiveness of adaptive CER strategies by maintaining the executive functions on which they rely. In this study, we carried out a secondary analysis of self-reported mental health and sleep data acquired during a protracted and naturally-occurring stressor - the COVID-19 pandemic - to firstly test the hypothesis that adaptive CER strategy use is associated with positive mental health outcomes and secondly, that the benefits of adaptive CER strategy use for mental health are contingent on high-quality sleep. Using established self-report tools, participants estimated their depression (N = 551) and anxiety (N = 590)2 levels, sleep quality and tendency to engage in adaptive and maladaptive CER strategies during the Spring and Autumn of 2020. Using a linear mixed modelling approach, we found that greater use of adaptive CER strategies and higher sleep quality were independently associated with lower self-reported depression and anxiety. However, adaptive CER strategy use was not a significant predictor of self-reported anxiety when accounting for sleep quality in our final model. The positive influence of adaptive CER strategy use on depression was observed at different levels of sleep quality. These findings highlight the importance of adaptive CER strategy use and good sleep quality in promoting resilience to depression and anxiety when experiencing chronic stress.

The relationship between sleep disturbance and cognitive impairment in mood disorders: A systematic review.

BACKGROUND: Cognitive impairment experienced by people with bipolar disorders (BD) or major depressive disorder (MDD) is associated with impaired psychosocial function and poorer quality of life. Sleep disturbance is another core symptom of mood disorders which may be associated with, and perhaps worsen, cognitive impairments. The aim of this systematic review was to critically assess the relationship between sleep disturbance and cognitive impairment in mood disorders. METHODS: In this systematic review, relevant studies were identified using electronic database searches of PsychINFO, MEDLINE, Embase and Web of Science. FINDINGS: Fourteen studies were included; eight investigated people with BD, five investigated people with MDD, and one included both people with MDD and people with BD. One study was an intervention for sleep disturbance and the remaining thirteen studies used either a longitudinal or cross-sectional observational design. Ten studies reported a significant association between subjectively measured sleep disturbance and cognitive impairment in people with MDD or BD after adjusting for demographic and clinical covariates, whereas no such association was found in healthy participants. Two studies reported a significant association between objectively measured (actigraphy or polysomnography) sleep abnormalities and cognitive impairment in mood disorders. One study of cognitive behavioural therapy for insomnia modified for BD (CBTI-BD) found an association between improvements in sleep and cognitive performance in BD. INTERPRETATION: There is preliminary evidence to suggest a significant association between sleep disturbance and cognitive impairment in mood disorders. These findings highlight the need for further research of sleep disturbances and cognitive impairment in people with mood disorders.

Sleep loss disrupts the neural signature of successful learning.

Sleep supports memory consolidation as well as next-day learning. The influential "Active Systems" account of offline consolidation suggests that sleep-associated memory processing paves the way for new learning, but empirical evidence in support of this idea is scarce. Using a within-subjects (n = 30), crossover design, we assessed behavioral and electrophysiological indices of episodic encoding after a night of sleep or total sleep deprivation in healthy adults (aged 18-25 years) and investigated whether behavioral performance was predicted by the overnight consolidation of episodic associations from the previous day. Sleep supported memory consolidation and next-day learning as compared to sleep deprivation. However, the magnitude of this sleep-associated consolidation benefit did not significantly predict the ability to form novel memories after sleep. Interestingly, sleep deprivation prompted a qualitative change in the neural signature of encoding: Whereas 12-20 Hz beta desynchronization-an established marker of successful encoding-was observed after sleep, sleep deprivation disrupted beta desynchrony during successful learning. Taken together, these findings suggest that effective learning depends on sleep but not necessarily on sleep-associated consolidation.

Targeted memory reactivation during sleep can induce forgetting of overlapping memories.

Memory reactivation during sleep can shape new memories into a long-term form. Reactivation of memories can be induced via the delivery of auditory cues during sleep. Although this targeted memory reactivation (TMR) approach can strengthen newly acquired memories, research has tended to focus on single associative memories. It is less clear how TMR affects retention for overlapping associative memories. This is critical, given that repeated retrieval of overlapping associations during wake can lead to forgetting, a phenomenon known as retrieval-induced forgetting (RIF). We asked whether a similar pattern of forgetting occurs when TMR is used to cue reactivation of overlapping pairwise associations during sleep. Participants learned overlapping pairs-learned separately, interleaved with other unrelated pairs. During sleep, we cued a subset of overlapping pairs using TMR. While TMR increased retention for the first encoded pairs, memory decreased for the second encoded pairs. This pattern of retention was only present for pairs not tested prior to sleep. The results suggest that TMR can lead to forgetting, an effect similar to RIF during wake. However, this effect did not extend to memories that had been strengthened via retrieval prior to sleep. We therefore provide evidence for a reactivation-induced forgetting effect during sleep.

Sleep bolsters schematically incongruent memories.

Our ability to recall memories is improved when sleep follows learning, suggesting that sleep facilitates memory consolidation. A number of factors are thought to influence the impact of sleep on newly learned information, such as whether or not we rehearse that information (e.g. via restudy or retrieval practice), or the extent to which the information is consistent with our pre-existing schematic knowledge. In this pre-registered, online study, we examined the effects of both rehearsal and schematic congruency on overnight consolidation. Participants learned noun-colour pairings (e.g. elephant-red) and rated each pairing as plausible or implausible before completing a baseline memory assessment. Afterwards, participants engaged in a period of restudy or retrieval practice for the pairings, and then entered a 12 h retention interval of overnight sleep or daytime wakefulness. Follow-up assessments were completed immediately after sleep or wake, and again 24 h after learning. Our data indicated that overnight consolidation was amplified for restudied relative to retested noun-colour pairings, but only when sleep occurred soon after learning. Furthermore, whereas plausible (i.e. schematically congruent) pairings were generally better remembered than implausible (i.e. schematically incongruent) pairings, the benefits of sleep were stronger for implausible relative to plausible memories. These findings challenge the notion that schema-conformant memories are preferentially strengthened during post-learning sleep.

Sounding It Out: Auditory Stimulation and Overnight Memory Processing.

PURPOSE OF REVIEW: Auditory stimulation is a technique that can enhance neural oscillations linked to overnight memory consolidation. In this review, we evaluate the impacts of auditory stimulation on the neural oscillations of sleep and associated memory processes in a variety of populations. RECENT FINDINGS: Cortical EEG recordings of slow-wave sleep (SWS) are characterised by two cardinal oscillations: slow oscillations (SOs) and sleep spindles. Auditory stimulation delivered in SWS enhances SOs and phase-coupled spindle activity in healthy children and adults, children with ADHD, adults with mild cognitive impairment and patients with major depression. Under certain conditions, auditory stimulation bolsters the benefits of SWS for memory consolidation, although further work is required to fully understand the factors affecting stimulation-related memory gains. Recent work has turned to rapid eye movement (REM) sleep, demonstrating that auditory stimulation can be used to manipulate REM sleep theta oscillations. SUMMARY: Auditory stimulation enhances oscillations linked to overnight memory processing and shows promise as a technique for enhancing the memory benefits of sleep.

Future-relevant memories are not selectively strengthened during sleep.

Overnight consolidation processes are thought to operate in a selective manner, such that important (i.e. future-relevant) memories are strengthened ahead of irrelevant information. Using an online protocol, we sought to replicate the seminal finding that the memory benefits of sleep are enhanced when people expect a future test [Wilhelm et al., 2011]. Participants memorised verbal paired associates to a criterion of 60 percent (Experiment 1) or 40 percent correct (Experiment 2) before a 12-hour delay containing overnight sleep (sleep group) or daytime wakefulness (wake group). Critically, half of the participants were informed that they would be tested again the following day, whereas the other half were told that they would carry out a different set of tasks. We observed a robust memory benefit of overnight consolidation, with the sleep group outperforming the wake group in both experiments. However, knowledge of an upcoming test had no impact on sleep-associated consolidation in either experiment, suggesting that overnight memory processes were not enhanced for future-relevant information. These findings, together with other failed replication attempts, show that sleep does not provide selective support to memories that are deemed relevant for the future.

No benefit of auditory closed-loop stimulation on memory for semantically-incongruent associations.

Auditory closed-loop stimulation has gained traction in recent years as a means of enhancing slow oscillatory activity and, consequently, sleep-associated memory consolidation. Previous studies on this topic have primarily focused on the consolidation of semantically-congruent associations. In this study, we investigated the effect of auditory closed-loop stimulation on the overnight retention of semantically-incongruent associations. Twelve healthy males (age: M = 20.06, SD = 2.02 years) participated in two experimental conditions (simulation and sham). In the stimulation condition, clicks were delivered in phase with slow oscillation up-states, whereas in the sham condition no auditory stimuli were applied. Corroborating earlier work, stimulation (vs. sham) enhanced the slow oscillation rhythm, phase-coupled spindle activity and slow oscillation power. However, there was no benefit of stimulation on overnight memory retention. These findings suggest that closed-loop stimulation does not benefit semantically-incongruent associations.

Sleep Loss Gives Rise to Intrusive Thoughts.

We propose a framework in which top-down inhibitory control networks are impaired by sleep deprivation, giving rise to intrusive thoughts and, consequently, emotion dysregulation. This process leads to a vicious cycle of sleeplessness, persistent unwanted thoughts, and heightened anxiety, ultimately increasing the risk of mental illness.

Losing Control: Sleep Deprivation Impairs the Suppression of Unwanted Thoughts.

Unwanted memories often enter conscious awareness when individuals confront reminders. People vary widely in their talents at suppressing such memory intrusions; however, the factors that govern suppression ability are poorly understood. We tested the hypothesis that successful memory control requires sleep. Following overnight sleep or total sleep deprivation, participants attempted to suppress intrusions of emotionally negative and neutral scenes when confronted with reminders. The sleep-deprived group experienced significantly more intrusions (unsuccessful suppressions) than the sleep group. Deficient control over intrusive thoughts had consequences: Whereas in rested participants suppression reduced behavioral and psychophysiological indices of negative affect for aversive memories, it had no such salutary effect for sleep-deprived participants. Our findings raise the possibility that sleep deprivation disrupts prefrontal control over medial temporal lobe structures that support memory and emotion. These data point to an important role of sleep disturbance in maintaining and exacerbating psychiatric conditions characterized by persistent, unwanted thoughts.

Sleep interventions for adults admitted to psychiatric inpatient settings: a scoping review protocol.

OBJECTIVE: The scoping review aims to identify how sleep is measured and what sleep interventions are used effectively in psychiatric inpatient settings. Potential barriers to measuring sleep in inpatient settings will be classified. INTRODUCTION: Polysomnography has shown that poor sleep is associated with emotional, cognitive, and somatic changes, as well as increased risks in suicide ideation and aggression. People with mental illness often experience sleep disturbances and believe the psychiatric inpatient environment contributes to sleep problems. The use of sleep interventions has been studied widely in general inpatient wards; less is known of similar interventions in psychiatric inpatient settings. INCLUSION CRITERIA: The review will include studies that focus on the effectiveness of sleep interventions for adults in any psychiatric inpatient setting. Studies that focus solely on sleep apnea, parasomnias, or restless legs syndrome will be excluded. METHODS: A literature search of PsycINFO, Web of Science, MEDLINE, and Google Scholar will be conducted. Studies identified will be screened and examined against the eligibility criteria. Only studies published in English will be considered, and there will be no date limitation applied to the search. Eligible studies will be assessed for risk of bias and relevant data will be extracted to answer the review questions. Extracted data will be presented in narrative and tabular formats.

Phase-locked auditory stimulation of theta oscillations during rapid eye movement sleep.

Auditory closed-loop stimulation is a non-invasive technique that has been widely used to augment slow oscillations during non-rapid eye movement sleep. Based on the principles of closed-loop stimulation, we developed a novel protocol for manipulating theta activity (3-7 Hz) in rapid eye movement (REM) sleep. Sixteen healthy young adults were studied in two overnight conditions: Stimulation and Sham. In the Stimulation condition, 1 s of 5 Hz amplitude-modulated white noise was delivered upon detection of two supra-threshold theta cycles throughout REM sleep. In the Sham condition, corresponding time points were marked but no stimulation was delivered. Auditory stimulation entrained EEG activity to 5 Hz and evoked a brief (~0.5 s) increase in theta power. Interestingly, this initial theta surge was immediately followed by a prolonged (~3 s) period of theta suppression. Stimulation also induced a prolonged (~2 s) increase in beta power. Our results provide the first demonstration that the REM sleep theta rhythm can be manipulated in a targeted manner via auditory stimulation. Accordingly, auditory stimulation might offer a fruitful avenue for investigating REM sleep electrophysiology and its relationship to behavior.

Sleep deprivation induces fragmented memory loss.

Sleep deprivation increases rates of forgetting in episodic memory. Yet, whether an extended lack of sleep alters the qualitative nature of forgetting is unknown. We compared forgetting of episodic memories across intervals of overnight sleep, daytime wakefulness, and overnight sleep deprivation. Item-level forgetting was amplified across daytime wakefulness and overnight sleep deprivation, as compared to sleep. Importantly, however, overnight sleep deprivation led to a further deficit in associative memory that was not observed after daytime wakefulness. These findings suggest that sleep deprivation induces fragmentation among item memories and their associations, altering the qualitative nature of episodic forgetting.

Investigating the formation and consolidation of incidentally learned trust.

People make inferences about the trustworthiness of others based on their observed gaze behavior. Faces that consistently look toward a target location are rated as more trustworthy than those that look away from the target. Representations of trust are important for future interactions; yet little is known about how they are consolidated in long-term memory. Sleep facilitates memory consolidation for incidentally learned information and may therefore support the retention of trust representations. We investigated the consolidation of trust inferences across periods of sleep or wakefulness. In addition, we employed a memory cueing procedure (targeted memory reactivation [TMR]) in a bid to strengthen certain trust memories over others. We observed no difference in the retention of trust inferences following delays of sleep or wakefulness, and there was no effect of TMR in either condition. Interestingly, trust inferences remained stable 1 week after learning, irrespective of the initial postlearning delay. A second experiment showed that this implicit learning occurs despite participants' being unable to explicitly recall the gaze behavior of specific faces immediately after encoding. Together, these results suggest that gist-like, social inferences are formed at the time of learning without retaining the original episodic memory and thus do not benefit from offline consolidation through replay. We discuss our findings in the context of a novel framework whereby trust judgments reflect an efficient, powerful, and adaptable storage device for social information. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Sleep Preserves Physiological Arousal in Emotional Memory.

Traumatic experiences are associated with increased emotional arousal. Overnight consolidation strengthens the episodic content of emotional memories, but it is still unclear how sleep influences the associated arousal response. To investigate this question, we compared the effects of sleep and wake on psychophysiological and subjective reactivity during emotional memory retrieval. Participants provided affective ratings for negative and neutral images while heart rate deceleration (HRD) and skin conductance responses (SCRs) were monitored. Following a 12-hour delay of sleep or wakefulness, participants completed an image recognition task where HRD, SCRs and affective ratings were recorded again. HRD responses to previously-encoded ("old") negative images were preserved after sleep but diminished after wakefulness. No between-group difference in HRD was observed for novel negative images at recognition, indicating that the effects of sleep for old images were not driven by a generalised overnight increase in visceral activity, or circadian factors. No significant effects of sleep were observed for SCRs or subjective ratings. Our data suggest that cardiac arousal experienced at the time of encoding is sensitive to plasticity-promoting processes during sleep in a similar manner to episodic aspects of emotional memory.