high-definition-transcranial-direct-current-stimulation-during-sleep

High-Definition Transcranial Direct Current Stimulation During Sleep

High-definition transcranial direct current stimulation (HD-tDCS) enables high spatial precision modulation of neural activity during sleep. This protocol ...

Beth Israel Deaconess Medical Center

Harvard Medical School

Recollecting painful or traumatic experiences can be deeply troubling. Sleep may offer an opportunity to reduce such suffering. We developed a procedure to weaken older aversive memories by reactivating newer positive memories during sleep. Participants viewed 48 nonsense words each paired with a unique aversive image, followed by an overnight sleep. In the next evening, participants learned associations between half of the words and additional positive images, creating interference. During the following non-rapid-eye-movement sleep, auditory memory cues were unobtrusively delivered. Upon waking, presenting cues associated with both aversive and positive images during sleep, as opposed to not presenting cues, weakened aversive memory recall while increasing positive memory intrusions. Substantiating these memory benefits, computational modeling revealed that cueing facilitated evidence accumulation toward positive affect judgments. Moreover, cue-elicited theta brain rhythms during sleep predominantly predicted the recall of positive memories. A noninvasive sleep intervention can thus modify aversive recollection and affective responses.

Aversive memories can be weakened during human sleep via the reactivation of positive interfering memories.

Experiencing trauma leads to intrusive memories (IMs), a hallmark symptom of post-traumatic stress disorder (PTSD), which also occurs transdiagnostically. Understanding why IMs increase or decrease is pivotal in developing interventions to support mental health. In this preregistered meta-analysis (PROSPERO: CRD42021224835), we included 134 articles (131 techniques, 606 effect sizes and 12,074 non-clinical participants) to investigate how experimental techniques alter IM frequency, intrusion-related distress and symptoms arising from lab-analogue trauma exposure. Eligible articles were identified by searching eight databases until 12 December 2023. To test potential publication biases, we employed methods including Egger's test and three-parameter selection models. We employed three-level multilevel modelling and meta-regressions to examine whether and how experimental techniques would modulate IM frequency and associated outcomes. Results showed that techniques (behavioural, pharmacological, neuromodulation) significantly reduced intrusion frequency (g = 0.16, 95% confidence interval [0.09, 0.23]). Notably, techniques aimed to reduce IMs also ameliorated intrusion-related distress and symptoms, while techniques that increased IMs exacerbated these related outcomes, thus highlighting IM's centrality in PTSD-like symptoms. Techniques tapping into mental imagery processing (for example, trauma reminder followed by playing Tetris) reduced intrusions when administered immediately after, or at a delayed time after trauma. Although our meta-analysis is limited to symptoms induced by lab-analogue trauma exposure, some lab-based results have now generalized to real-world trauma and IMs, highlighting the promising utility of lab-analogue trauma paradigms for intervention development.

A systematic review and meta-analysis of experimental methods for modulating intrusive memories following lab-analogue trauma exposure in non-clinical populations.

Disturbed sleep is a known risk factor for heightened mental health symptoms, and this association may be particularly problematic among emergency medical service (EMS) clinicians. Yet, associations between daily sleep quality and daily mental health symptoms are understudied among this vulnerable group. We used ecological momentary assessments to examine between- and within-person associations between perceived sleep quality and mental health symptoms in 79 EMS clinicians employed at a large agency in central New York. Participants completed eight daily assessments (558 total) on perceived sleep quality and symptoms of posttraumatic stress disorder (PTSD) and depression. Multilevel regression models examined between- and within-person effects of sleep quality, controlling for covariates. Between-person effects in each model accounted for 17.0% and 31.0% of the total variance, respectively; within-person effects explained 1.0% per model. Poorer between-person perceived sleep quality was associated with higher PTSD and depressive symptom severity; perceived sleep quality 1.0 standard deviation (SD) below the sample mean was related to 58.8% and 16.3% increases in PTSD and depressive symptoms, respectively. There was also a within-person effect for depressive symptoms: On days when a participant's perceived sleep quality was 1.0 SD below their average, depressive symptom severity increased by 3.0%. Poorer subjective sleep may be an important risk factor for mental health symptoms at the between-person level. EMS policies supporting healthy sleep may benefit clinicians who routinely experience poor sleep. Day-to-day subjective sleep quality may increase the risk for depressive symptoms. Interventions to improve sleep and manage depressive symptom fluctuations when sleep is poor might be helpful.

Examining the between- and within-person associations among perceived sleep quality and mental health symptoms in emergency medical service clinicians.

Human memory tends to bias negative over neutral information. Recent evidence suggests that this bias may be due to a categorical effect of emotionally salient information, which diminishes when negative information is less frequent. Moreover, sleep loss has been shown to impair memory. Here, we aimed to replicate this categorical-over valence-bias for emotional information and determine the influence of total sleep deprivation (TSD) on this effect.

The categorical effect of negative emotion on memory before and after sleep deprivation.

Memories can involuntarily come to mind out of nowhere. These spontaneous flashes often feel vivid and emotionally powerful. A new study in PLOS Biology reveals that involuntary and voluntary memory rely on distinct brain mechanisms.

How does the brain remember? Distinct pathways for voluntary and involuntary recall.

Sleep consolidates memories. Yet how sleep preserves precise memories while transforming them into abstract and categorical knowledge remains unclear. Using electroencephalography and representational similarity analysis, we examined memory representational transformation across overnight sleep. We focused on item-level representations, which reflect specific details of individual memories, and category-level representations, which capture shared conceptual features across items from the same category. Our results showed that after sleep, item-level representations were reduced, while category-level representations were preserved. Notably, a higher ratio of rapid eye movement (REM) to slow-wave sleep (SWS) predicted greater item-level reduction and category-level enhancement. Additionally, theta (4-7 Hz) and beta (15-25 Hz) power during REM sleep were positively associated with these memory representational transformations, whereas slow oscillation-related (1-1.25 Hz) power during SWS showed the opposite pattern. Our findings suggest the differential roles of SWS and REM in balancing memory preservation and transformation.

Article	Year
Aversive memories can be weakened during human sleep via the reactivation of positive interfering memories. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 39052838	2024
A systematic review and meta-analysis of experimental methods for modulating intrusive memories following lab-analogue trauma exposure in non-clinical populations. Nature human behaviour\| PubMed ID: 39169230	2024
Examining the between- and within-person associations among perceived sleep quality and mental health symptoms in emergency medical service clinicians. Journal of traumatic stress\| PubMed ID: 40501003	2025
The categorical effect of negative emotion on memory before and after sleep deprivation. Neuropsychologia\| PubMed ID: 40543569	2025
How does the brain remember? Distinct pathways for voluntary and involuntary recall. PLoS biology\| PubMed ID: 40834027	2025
Slow-wave sleep and REM sleep differentially contribute to memory representational transformation. Communications biology\| PubMed ID: 41034492	2025
Does Poor Sleep Fuel Emotional Suppression? A Three-Wave RI-CLPM in Chinese Adolescents Reveals Sex-based Cultural Mechanisms. Journal of youth and adolescence\| PubMed ID: 41123824	2025

Shengzi Zeng

Biography

JoVE Journal Publications

Other Publications