bluuebunny/crossref_metadata_2025 huggingface dataset:
0046 A Mechanism by Which Estradiol (E2) Regulates Adenosinergic Signaling in the Median Preoptic Nucleus (MnPO)
Authors: Kruk Katie , Mong Jessica , Viechweg Shaun , Byrd Carissa
Published: April 2024

Introduction

Women report more sleep difficulties than men, particularly during times of hormonal fluctuations. This indicates that sex hormones likely play a role in a woman’s sleep-wake cycle, but the mechanism by which they do so is largely unknown. We have previously shown that estradiol (E2) increases wake and decreases NREM sleep in female rats, and that E2 action in the median preoptic nucleus (MnPO), a major sleep center in the brain, is necessary and sufficient to induce wakefulness. Additionally, in the MnPO, E2 increases extracellular adenosine, which is known to induce NREM sleep via activation of the A2A adenosine receptor (A2AR). Our previous work demonstrated that an A2AR agonist infused in the MnPO is not able to mediate its pro-sleep effects in the presence of E2, and the current work investigates a mechanism for this finding. Our preliminary data shows that E2 upregulates the mRNA of an orphan receptor, GPR37, in the MnPO; GPR37 has been shown to form heteromers with A2AR and reduce the expression and function of A2AR in the striatum. We hypothesize that E2-induced upregulation of GPR37 leads to inhibition of A2AR in the MnPO, thus preventing its pro-sleep effects.

Methods

To examine mRNA and protein expression, ovariectomized female rats were treated with subcutaneous injections of E2 or oil for two days and sacrificed on the third day, where their brains were collected. To examine if GPR37 knockdown in the MnPO affects E2’s ability to induce wakefulness, a GPR37 shRNA virus or scramble virus control was injected into the MnPO of female rats; they were also ovariectomized and had telemeters implanted to measure sleep-wake states in the presence of oil and E2.

Results

We found that E2 increases GPR37 mRNA and protein expression while decreasing A2AR mRNA expression in the MnPO. Furthermore, we found that knockdown of GPR37 in the MnPO significantly attenuates the effects of E2 on wakefulness, NREM sleep, and REM sleep in the dark phase but not the light phase.

Conclusion

E2 appears to have an effect on the sleep/wake phenotype through adenosinergic signaling and expression in the MnPO through E2-induced upregulation of GPR37.

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0047 Intracranial EEG Reveals Human Cerebral Cortical Regions That Are Spared from Alpha-delta Sleep
Authors: Liu Junjie , Asgarli Aygun , Banks Matthew , Nourski Kirill
Published: April 2024

Introduction

Alpha-delta sleep, also known as alpha wave intrusion during sleep, is an electroencephalography (EEG) pattern often observed in clinical settings, and is associated with unrefreshing sleep and chronic fatigue or pain. The neural basis of alpha-delta sleep is poorly understood, and the extent of the cerebral cortex’s involvement is unknown. Here we use overnight intracranial and scalp EEG in adult humans to explore the cortical neural mechanisms of alpha-delta sleep.

Methods

We studied neurosurgical epilepsy patients who underwent longitudinal intracranial EEG (iEEG) monitoring. In each patient, data were simultaneously recorded overnight from iEEG electrodes and electrodes placed on scalp for polysomnography. To focus on local neural activity, we derived each iEEG channel as the signal difference between two adjacent recording sites separated by 5 mm within the cerebral cortex. For each 30-second epoch, we calculated EEG power in delta (1-4 Hz), theta (4-8 Hz), and alpha (8-15 Hz) frequency bands for all iEEG channels, and for sleep-scoring scalp EEG channels (e.g. C3-A2). Other bands were studied to rule out the effects of sleep spindles. For each night (comprising around 1000 epochs), we calculated the Spearman’s rank correlation coefficients of the EEG power values across epochs between the delta-band and the alpha-band power in each channel.

Results

All scalp EEG and most iEEG channels showed large increases of delta-band power during non-REM sleep compared to awake. Many (> 75%) of these channels also showed significant increases of alpha-band power, and positive correlations across overnight epochs between delta-band and alpha-band power, indicating involvement of alpha-delta sleep. However, a minority (< 25%) of iEEG channels, often located in the temporal lobe, showed significant decreases of alpha-band power during non-REM sleep compared to awake, and negative correlations between delta-band and alpha-band power, therefore appearing to be not involved in alpha-delta sleep.

Conclusion

Our iEEG study showed for the first time that alpha-delta sleep is not homogeneous across the cerebral cortex. Instead, the cortical distribution of alpha waves is more spatially restricted than the distribution of delta waves during non-REM sleep. This finding sheds new light on the neural basis of alpha-delta sleep.

Support (if any)

NIH R01-GM109086 (to M.I.B, K.V.N.)
0051 The Melanocortin and Endorphin Neuropeptides in Patients with Restless Legs Syndrome
Authors: Koo Brian , Abdelfattah Ahmed , Eysa Athar , Lu Lingeng
Published: April 2024

Introduction

Based upon similarities between the urge to move and sensory discomfort of restless legs syndrome (RLS) and properties of melanocortin hormones, like their incitement of movement and hyperalgesia, we assessed plasma and cerebrospinal fluid (CSF) α-melanocyte stimulating hormone (α-MSH) and β-endorphin in RLS patients and controls.

Methods

Forty-two untreated moderate-to-severe RLS patients and 44 matched controls underwent venipuncture at 19:00PM, 20:30PM, and 22:00PM; 37 RLS and 36 controls had lumbar puncture at 21:30PM. CSF and plasma were analyzed for pro-opiomelanocortin (POMC), adrenocorticotropin hormone (ACTH), α-MSH, β-MSH, and β-endorphin by immunoassay. RLS severity was assessed by International RLS Study Group Severity Scale.

Results

RLS participants were 52.7±12.0 years; 61.9% women; 21.4% painful RLS; RLS severity 24.8±9.0. Controls had similar age and sex. Plasma ACTH, α-MSH, and β-endorphin were similar between groups. Plasma POMC was significantly greater in RLS than controls (17.0±11.5 vs. 12.7±6.1 fmol/mL; p=0.048). CSF ACTH was similar between groups. CSF β-MSH was significantly higher in painful than non-painful RLS or controls (48.2±24.8 vs. 32.1±14.8 vs. 32.6±15.2 pg/mL; ANOVA p=0.03). CSF α-MSH was higher in RLS than controls (34.2±40.9 vs. 20.3±11.0 pg/mL; p=0.062). CSF β-EDP was lowest in painful RLS, intermediate in non-painful RLS, and highest in controls (8.0±3.4 vs. 10.8±3.1 vs. 12.3±5.0 pg/mL; ANOVA p=0.049). The ratio of the sum of CSF α- and β-MSH to CSF β-endorphin was highest, intermediate, and lowest in painful, non-painful RLS, and controls (p=0.007).

Conclusion

CSF α- and β-MSH are increased and CSF β-endorphin decreased in RLS patients, particularly for painful RLS.

Support (if any)

This work was supported by a Department of Defense Discovery Award grant, part of the Peer Reviewed Medical Research Program and the Congressionally Directed Medical Research Program (CRMRP). The grant was entitled Restless Legs Syndrome and the Melanocortin System; grant number W81XWH2010003.
0053 The Temporal Dynamics of Emotional Memory and Reactivity in Patients with Insomnia Disorder
Authors: Zeng Shengzi , Sit Hao Fong , Bottary Ryan , Pace-Schott Edward , Cunningham Tony , Li Shirley Xin , Hu Xiaoqing
Published: April 2024

Introduction

Insomnia is commonly linked with mood and anxiety-related disorders characterized by disrupted emotional memory processing. However, much remains unknown about the neurocognitive mechanisms underlying emotional memory processing among patients with insomnia. The current study seeks to examine the temporal dynamics of emotional memory processing among both patients with insomnia and healthy sleepers.

Methods

Thirty-four patients with DSM-5 insomnia disorder (23 females; Mage = 24.94) and 35 healthy sleepers (23 females; Mage = 23.91) encoded 48 pairs of pseudo-words and negative/neutral scene pictures in the evening, followed by overnight EEG-recorded sleep. All participants completed cued-recall memory tasks and affective ratings at pre-sleep, post-sleep, and 7-day delayed sessions.

Results

From the post-sleep to 7-day delayed sessions, patients with insomnia showed greater preservation of pictorial memory (ps < 0.001) and less dissipation of affective tone compared to the healthy sleepers (ps < 0.016). Moreover, among healthy sleepers, the product of post-encoding slow wave sleep (SWS) and rapid eye movement (REM) sleep duration predicted greater over-time negative memory decay (b = -0.001, p = 0.035), whereas REM duration predicted the dissipation of negative arousal ratings over time (b = -0.03, p = 0.041). Notably, these associations were not observed in the insomnia group.

Conclusion

These findings provide insight into the fundamental irregularities in emotional memory processing among patients with insomnia. For healthy sleepers, the results suggest a joint engagement of SWS and REM in promoting negative memory decay, and an adaptive role of REM sleep in facilitating the attenuation of affective arousal over time.

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0056 Overnight Memory Consolidation in Adolescents: Effects of Change in DLMO Phase After Sleep Restriction
Authors: Stager Lindsay , Gredvig-Ardito Caroline , Carskadon Mary , Saletin Jared
Published: April 2024

Introduction

Sleep aids learning and memory. Limited studies have examined how circadian rhythms moderate this process, particularly in adolescents who experience developmental changes in circadian biology. Here we examine how sleep restriction, memory consolidation, and circadian biology interact in youth with distinct circadian phase preferences.

Methods

Adolescents were recruited based on circadian phase preference on the Morningness/Eveningness (M/E; Carskadon et al., 1993) scale. Sixteen participants entered the current analysis (6F, 2 Non-White; age 10-15, mean±sd:12.69±1.76 years; M/E 22-40; mean±sd: 33.38±5.78; 1 Evening-Type [M/E≤23]; 4 Neither Type [23>M/E< 34]; 11 Morning type]). All completed 19 nights of stabilization on a self-selected 9-hour in bed schedule followed by 7 nights of sleep restriction (6.5 hours in bed; bedtime delayed and rise time advanced equally). In-lab dim-light-melatonin-onset (DLMO) assessment occurred on the final nights of stabilization and restriction. Overnight memory consolidation was indexed on the motor sequence task (MST; Walker et al., 2006) across the final night of sleep restriction. Memory outcomes included speed (# correct sequences), # of errors, and precision (speed-error trade-off). We examined overnight improvement (morning-evening) in MST performance and associations between improvement, phase preference score, stabilized DLMO phase, and the DLMO phase change after restriction (negative numbers indicate phase delay). Regressions controlled for age where statistically justified.

Results

MST speed improved (t(15)=-3.44, p<.01, d=0.86) for the morning (12.94±6.89) test session compared to evening (10.81±5.69). There were no overnight changes in errors or precision (d’s<.14, p’s>.34). Overnight improvement was not related to M/E phase preference (Adj. R2’s< 0.17; p’s>.05); however, there was a significant association between the change in DLMO phase (mean±sd: 10.34±41.69 minutes) and memory consolidation for both speed (Adj. R2=0.54, F(2,13)=9.79, p<.01) and errors (Adj. R2=0.21, F(1,15)=4.94, p<.05). Specifically, children with a greater delay in DLMO phase demonstrated greater overnight improvement on the MST.

Conclusion

These data indicate a potential link between circadian biology and the cognitive benefits of sleep during adolescence. These findings are significant given the shifts in circadian rhythms occurring across adolescence. Understanding the influence of circadian rhythms in sleep-dependent memory may inform discussions of how sleep loss affects learning in school-aged youth.

Support (if any)

R01NR08381 and P20GM139743
0057 Functional Network Architecture Supports Memory Consolidation via NREM Sleep Oscillation Expression and Coupling
Authors: Chappel-Farley Miranda G , Adams Jenna , Sattari Negin , Berisha Destiny , Meza Novelle , Janecek John , Betzel Richard , Niknazar Hamid , Kim Soyun , Dave Abhishek , Chen Ivy Y , Lui Kitty K , Benca Ruth , Yassa Michael , Mander Bryce
Published: April 2024

Introduction

Memory consolidation is facilitated by trace reactivation during non-rapid eye movement slow wave sleep (SWS), involving reinstatement of a hippocampal index driving integration of activity patterns stored in cortical modules. Slow oscillation (SO) and sleep spindle (SP) coupling reflects this process. Here, we used a novel graph theory approach to examine whether network modularity (Q) and the relative import of the hippocampus and amygdala in network function, measured by eigenvector centrality (EC) and betweenness centrality (BC), are associated with SWS expression, SO-SP coupling, and emotional memory consolidation.

Methods

Thirty-six cognitively intact older adults (μ=72.9±5.6 years, 23 Females) completed structural and resting-state functional magnetic resonance imaging (MRI) at 3T, an overnight polysomnography with electroencephalography, and, prior to and following sleep, performed the Emotional Mnemonic Discrimination Task, with the Lure Discrimination Index quantifying memory. MRI data were preprocessed with the CONN toolbox. Network nodes were defined using the Brainnetome atlas. Graph metrics were computed using the Brain Connectivity Toolbox. In a subset, p-welch derived SO power (N=18) and mean vector length computed phase-amplitude SO-SP coupling (N=16) were derived.

Results

Q was associated with diminished emotional memory retention (B=-1.394, p=0.042) and greater SWS percentage (B=48.476, p=0.023), which was also associated with emotional memory retention (B=0.013, p=0.020). An inconsistent mediation effect of SWS in the Q-emotional memory retention relationship was found (95% CIs: 0.015, 0.345). Hippocampal EC (B=36.845, p=0.008) and amygdala EC (B=47.277, p=0.022) were associated with emotional memory retention. Hippocampal BC was associated with immediate test performance (B=19.859, p=0.027), whereas amygdala BC was associated with delayed test (B=1.823, SE=0.745, p=0.020) and emotional memory retention (B=1.699, p=0.047). Hippocampal EC (B=0.475, p=0.047) and BC (B=0.426, p=0.086) were associated with frontal SO expression, which was associated with delayed test performance (B=0.492, p=0.038). Hippocampal EC (B=0.649, p=0.006) and amygdala BC (B=0.545, p=0.029) were associated with frontal SO-SP coupling.

Conclusion

These findings suggest that greater network integration supports SWS-dependent emotional memory consolidation during sleep. A more topologically influential hippocampus aids in memory acquisition and retention, whereas a more influential amygdala supports emotional memory consolidation.

Support (if any)

This research was supported by NIA grants F31AG074703, F32AG074621, R21AG07955, R01AG053555, K01AG058353, and AASM Foundation SRA-1818.
0060 A Meta-Analytic Investigation of the Effect of Sleep Deprivation on Inhibitory Control
Authors: Choong Sze Yinn , Byrne Jamie E M , Lum Jarrad A G , Staiger Petra K , Jones Andrew , Rispoli-Yovanovic Maris , Drummond Sean P A
Published: April 2024

Introduction

Research has suggested that varying degrees of sleep deprivation have a detrimental effect on inhibitory control (a collection of neural processes evoked to suppress a prepotent response). This is the first meta-analysis to assess the impact of sleep deprivation on inhibitory control in controlled studies.

Methods

The review was performed following PRISMA guidelines. Four electronic databases, APAPsycINFO, Medline, CINAHL and Embase, were systematically searched from inception to November 2023. Selection criteria included studies that conducted experimentally induced sleep disruption (sleep deprivation protocols) in healthy adults (aged above 18 years, no sleep-related/mental disorders/cognitive impairments) and reported inhibitory control performance defined by the Go/No-Go and/or Stop-Signal Task paradigms. Quality appraisal was assessed using the revised Cochrane Risk-of-Bias Tool for Randomised Trials (RoB 2) and Risk of Bias in Non-Randomised Studies of Interventions (ROBINS-I). Effect sizes (Hedge’s g) examining the impact of sleep deprivation on inhibitory control were pooled using random-effects meta-analysis.

Results

Twenty-four studies (n = 712 participants) were included. Sleep deprivation protocols included total sleep deprivation (N= 21 studies), partial sleep deprivation (N= 2) and both (N= 1). Seventeen studies used the Go/No-Go Task, and seven studies used the Stop Signal Task. The meta-analysis showed sleep deprivation negatively affected inhibitory control as measured by the Go/No-Go and Stop-Signal (Hedge’s g = 0.481, [95% CI: 0.361 to 0.600], p < .001, I2 = 43%). Sleep deprivation effects were similar across Go/No-Go (Hedge’s g = 0.475, [95% CI: 0.346 to 0.604], p < .001, I2 =34%) and Stop-Signal performance (Hedge’s g = 0.482, [95% CI: 0.190 to 0.773], p < .001, I2 =63%).

Conclusion

Our findings demonstrate that sleep deprivation has a significant negative impact on inhibitory control as measured by Go/No-Go and Stop-Signal. These results have important implications regarding the impacts of sleep deprivation on the ability to suppress prepotent responses. Resultant impaired decision-making, higher levels of risk-taking behaviours and difficulties in stopping and modifying planned actions may have real-world consequences for workplace or vehicular safety.

Support (if any)

Deakin University Postgraduate Research Scholarship (DUPRS)
0062 Memory for Text Meaning Is Maintained During 24 Hours of Continuous Wakefulness
Authors: Kurinec Courtney , Whitney Paul , Hinson John , Van Dongen Hans
Published: April 2024

Introduction

Total sleep deprivation (TSD) has been shown to impair associative memory, but little is known about the effects of TSD on memory for naturalistic text. Naturalistic text has different levels of representation: memory for surface form (verbatim text), which is short-lived; memory for textbase (ideas expressed in the text); and event model (representation of the situation described in the text). We investigated whether TSD differentially impacts memory by level of representation.

Methods

N=10 female active-duty dayshift (DS; n=5) and nightshift (NS; n=5) workers (ages 35.1±8.1y) matched by age participated in a 36h laboratory study. After waking at their habitual wake time (DS: 05:57±64min; NS: 12:52±62min) and working their normal shift, participants arrived at the laboratory at 08:00 (DS) or 20:00 (NS). Following a 2h acclimation period, participants completed a 24h constant routine protocol with continuous wakefulness, followed by recovery sleep 1h later. 1h into the constant routine, participants read three narrative texts (self-paced). Memory for text was tested immediately (3h awake), 1h later (4h awake), and 24h later (27h awake). Participants saw 64 recognition probes per text, which varied by whether they required memory for surface form, textbase, or event model. Discriminability indices were calculated for each level of representation.

Results

Mixed-effects ANOVA with fixed effects of test bout (0h, 1h, 24h after reading), level of representation, and their interaction, covariates for shift and age, and a random intercept over participants showed a significant effect for level of representation (F=32.17, p< 0.001). Memory for surface form, which was near chance levels, was worse (p< 0.05) than that for textbase and event model, which did not differ from each other (p=0.271). There was no significant effect for test bout (p>0.1).

Conclusion

Memory for naturalistic text was not significantly impaired by 24h TSD. Memory for surface form was at chance level throughout, as expected since it is known to be short-lived. However, memory for textbase and event model, which reflect text meaning, was retained despite the anticipated impact of TSD on associative memory. The widespread associations in texts may provide more cues to facilitate retrieval and maintain memory performance during TSD.

Support (if any)

CARE Fund FY22-POP-02; HSSA
0063 Sleep Deprivation Impairs Short-term Object Recall on a Serial Novel Object Recognition Task in Rats
Authors: Fluke Sofia , Satterfield Brieann , Davis Christopher
Published: April 2024

Introduction

Novel Object Recognition (NOR) is a rodent behavioral task used to test recall based on the time taken to explore a novel versus familiar object. Sleep deprivation (SD) compromises object discrimination, but time of day and interphase interval (IPI) are important to performance. While the effects of SD on NOR have been investigated with a single object recall opportunity, SD preceding short-term recall combined with serial trials has not been reported. Serial paradigms are important for establishing baseline performance and predicting future performance altered by practice effect and habituation. Here we present a unique serial NOR paradigm that assesses baseline performance, SD, and IPI effects.

Methods

Male Sprague Dawley rats (N=20) were housed on a ZT0-ZT12 light cycle with baseline NOR testing at ZT12. Ten rats were randomly assigned to SD during the light cycle and the remaining controls slept undisturbed. Treatment testing also occurred at ZT12, after which SD rats were allowed to sleep, and recovery testing followed at ZT14 or ZT16. Each testing session included three phases: acclimation (no objects), familiarization (identical objects), and recognition (novel/identical objects) with < 4 minutes between phases. The recognition phase object discrimination ratio (DR) was analyzed using a mixed-effects ANOVA, with fixed effects of testing (baseline, treatment, recovery), group (control, SD), and their interaction. Secondary analyses assessed the effect of recovery-delay timing (ZT14, ZT16).

Results

There was a significant main effect of group (F[1,18]=7.64,p=0.013) and group by test interaction (F[2,36]=6.52,p=0.004). There were no differences between groups at baseline or recovery and no differences in recovery-delay. During the treatment test, SD rats were unable to recognize the novel object compared to controls (p< 0.001), spending more time with the familiar object (p< 0.001). Control rat performance worsened at recovery compared to treatment (p=0.033).

Conclusion

The serial NOR established baseline performance, which was associated with behavioral changes over time. SD significantly inhibited short-term recall, while controls presented stable performance from baseline to treatment testing, with significant performance deficits from treatment to recovery. This decrement may stem from habituation due to a short IPI and/or a time-of-day effect.

Support (if any)

WSU College of Medicine Department of Translational Medicine and Physiology
0066 Reactivating Remote Emotional Memory Before Sleep Impacts Dream Affect, but Not Dream Content
Authors: Frost Chadwick , Middleton Taya , Wamsley Erin
Published: April 2024

Introduction

Completing a learning task just before sleep often induces task-related dreams. This is thought to reflect the consolidation of recently formed memories in the sleeping brain. However, this literature has focused almost exclusively on how recent experiences newly introduced before sleep are incorporated into dreams. It is unknown whether and how remote memories may also be reactivated during sleep and incorporated into dreaming.

Methods

We aimed to experimentally trigger participants to dream about a remote emotional episodic memory. Just before a nap, participants (N = 34) completed the Autobiographical Emotional Memory Task (AEMT). In this task, participants were asked to recall and write about “the one situation that has made you the most angry you have been in your life”. In a control condition (within-subjects), participants instead wrote about designing a new college course. During the subsequent nap, participants were awoken up to four times to report their dream experiences. Following the nap, participants rated the extent to which they felt each dream was related to the earlier writing task, and rated the emotional valence of each dream.

Results

The AEMT elicited negative mood (pre-nap PANAS-negative score in AEMT vs. control condition: t(33)= 6.20, p< 0.0001). Although participants rated some dreams as related to the pre-sleep writing task in both conditions, dreams were not significantly more related following the AEMT, as compared to the control condition (Wald test: χ2(1)=2.67, p=0.10). However, dream emotion was significantly more negative following the AEMT, relative to the control condition (Wald test: χ2(1)=5.15, p=0.02). This effect was strongest for the first dream reported.

Conclusion

Recalling a personal memory had no greater influence on dream content than writing about a neutral, memory-nrelated topic. At the same time, recalling a remote, emotional memory before sleep did affect the emotional valence of dreams. These data echo observations dating back to the 1960s suggesting that while transparent representations of presleep experience in dreams are rare, emotional stimuli do reliably influence dream affect. This might reflect emotional memory consolidation, or be a more general influence of pre-sleep mood on subsequent emotion during sleep.

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0067 The Effect of Aging on Emotional Memory Encoding and Consolidation over Sleep and Wake
Authors: Rodheim Katrina , Jones Bethany , Spencer Rebecca
Published: April 2024

Introduction

Sleep is essential for the consolidation of emotional memories. Young adults exhibit a bias towards consolidation of negative memories over sleep while older adults exhibit a bias towards consolidation of positive memories over sleep. As this parallels known biases in emotional memory encoding, it is unclear whether biases found after sleep are simply carried over from biases prior to sleep or if sleep amplifies emotional memory biases. Thus, the present study assessed emotional memory before and after intervals of sleep and wake to determine whether sleep biases the selectivity of emotional memory.

Methods

Healthy younger (N=52, 18-30 years; YA) and older adults (N=38, 50-80 years; OA) completed two conditions: a positive and negative emotional memory task. Emotional images were viewed followed by an immediate recognition assessment before overnight sleep (Sleep group; YA=29, OA=19) or before a day of wakefulness (Wake group; YA=23, OA=19). Delayed recognition was assessed approximately 12-hrs later. For the Sleep group, polysomnography was recorded. To assess differences in memory change (delayed minus immediate recognition) between condition (negative vs. positive), group (Sleep vs. Wake) and age (YA vs. OA), ANOVAs were conducted.

Results

There was a significant interaction between the effects of condition (positive vs. negative) and group (sleep vs. wake) (p=0.03) such that sleep (relative to wake) benefitted negative but not positive memories regardless of age. Investigating age groups separately, both younger (p=0.06) and older (p=0.06) adults tended to display this interaction. We next considered change in negative memory bias (negative – positive performance) between immediate and delayed recognition. There was a near-significant main effect of group (p=0.06), indicating that negative bias increased in the sleep compared to wake group.

Conclusion

These findings suggest sleep may impart a negative memory bias. This is consistent with our prior work in young adults but unexpected in older adults. This may suggest that, like young adults, healthy older adults preferentially consolidate negative over positive emotional memories during a night of sleep. Therefore, sleep-dependent emotional memory consolidation may be preserved even as sleep and memory decline with aging. Future analysis will examine associations between sleep architecture and emotional memory performance.

Support (if any)

NIH R01AG040133(PI: Spencer)
0068 The Impact of Transcutaneous Vagal Nerve Stimulation on Sleep-Dependent Emotional Memory
Authors: Perez Rene , Whitehurst Lauren , Subramoniam Anjana , Gilmore Gabriel
Published: April 2024

Introduction

The autonomic nervous system (ANS) supports memory, with peripheral activity, through the vagus nerve, enriching or impairing acquisition and consolidation, especially for emotional experiences. Sleep is critical for memory consolidation and has been implicated in affective regulation. Yet, the causal impact of the ANS during sleep for memory has not been rigorously assessed. The current project examined the impact of non-invasive vagal nerve stimulation during sleep on emotional memory consolidation

Methods

24 participants (Mean age = 22.82; 13 Male; 11 Female) completed two nights of polysomnographic recordings - one with 90-mins of active transcutaneous vagal nerve stimulation during NREM sleep and one with sham stimulation - counterbalanced across participants. Emotional memory was assessed via a picture recognition task. Sixty images were presented during a pre-sleep encoding session (30 negative and 30 neutral). Recognition memory (15 old/negative, 15 old/neutral, 15 new/negative and 15 new/neutral) was assessed twice, 30-mins after encoding (Test 1) and post-sleep (Test 2). Outcome metrics included d’ (sensitivity), c (bias criterion), and c’ (corrected sensitivity). Change scores (Test 2 -1) were calculated. Mixed-model repeated measures ANOVAs with self-reported biological sex as a between-subjects factor were used to assess the impact of stimulation (active vs sham) and valence conditions (negative vs neutral) on memory processing.

Results

For d’, a significant sexXstimulation interaction emerged, F(1,22)=6.66,p =0.017. Male participants performed better in the sham condition (p=0.035), but this effect was attenuated in the stimulation condition (p=0.236). Participants exercised a stricter criterion when receiving active vs. sham stimulation and were less likely to indicate that they remembered stimuli that they viewed during encoding at test (p=.051). Given this, we examined c’ to adjust for response bias. We found a significant effect of emotion (p=.025) and a marginal effect of stimulation condition (p=.058). Across sleep, participants were better at discriminating between previously encoded neutral images than negative images. Sleep-dependent discrimination performance also improved after active stimulation (c’=0.086) but declined under sham (c’=-0.018; p=.058).

Conclusion

These are the first data to suggest causal links between sleep-dependent autonomic activity and next-day memory processing. Analyses of polysomnographic sleep features linked to these outcomes are in progress.

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0071 Does Additional Training on a Motor Sequence Task Improve Sleep-Dependent Memory Consolidation for Older Adults?
Authors: Delvey Cassandra , Rodheim Katrina , Jones Bethany , Spencer Rebecca
Published: April 2024

Introduction

While sleep can improve memory performance, not all memory domains demonstrate this effect. Prior studies show that hippocampal engagement during encoding is necessary for subsequent sleep-dependent memory consolidation. However, motor sequence learning typically engages other areas and inconsistently demonstrates sleep-related gains, particularly among older adults. Hippocampal engagement via explicit sequence awareness and strong learning ability increases the possibility of sleep-related procedural memory gains. Therefore, we compared sleep-dependent memory consolidation on an explicit motor sequence task in older adults who received standard training to those who received additional training.

Methods

Healthy older adults (N=24; 67.7 ± 4.5 years; 71% female), assigned to a standard training group (n=12) or an over-training group (n=12), were trained on an explicit motor sequence learning task; standard training comprised 5 blocks of practice while over-training included 10. Performance was tested before (“immediate”) and after (“delayed”) a day spent awake and a night spent asleep (conditions separated by ~1 week, order counterbalanced). Skill learning was calculated by subtracting median reaction time during learned sequences from that of randomly-cued button presses. Change in skill learning from immediate to delayed test for the wake interval was contrasted with change across sleep, resulting in a sleep benefit score. Sleepiness was assessed using the Stanford Sleepiness Scale prior to each testing session. Polysomnography (32-channel, Brainvision) was recorded during the overnight sleep visit.

Results

A planned comparison of immediate test results, to check baseline differences resulting from training, showed that the over-training group was significantly faster than the standard training group (t(23)=4.796, p<.001, d=1.18). Analysis of sleep benefit scores showed no significant benefit with standard training (t(11)=0.778, p=.453) or over-training (t(10)=1.342, p=.209), and over-training does not provide a significantly greater sleep benefit than standard training (t(23)=4.796, p=.590).

Conclusion

Our results replicate prior findings that standard training of a motor sequence task in older adults does not demonstrate sleep-dependent memory gains. Moreover, here we show that additional training does not improve the chances of demonstrating such gains, despite significantly improving initial performance. Because sleep spindles have been previously linked to motor sequence learning across sleep, future analysis will include polysomnography recordings.

Support (if any)

NIH R01 HL111695
0072 Preliminary Steps Towards an Overnight Intervention to Help Individuals with Age-related Memory Difficulties
Authors: Yamazaki Erika , Whitmore Nathan , Paller Ken
Published: April 2024

Introduction

Sleep supports memory consolidation and can prevent memories from being forgotten. Targeted Memory Reactivation (TMR) is an experimental technique that boosts the natural replay of recently acquired memories during sleep and can bias which memories are consolidated. TMR has been applied in many experiments by softly playing sounds associated with specific memories during slow-wave sleep, while not disrupting sleep. We developed a TMR algorithm that can be used in the home, with the future goal of decreasing forgetting for certain high-value information in seniors, particularly those with early-stage Alzheimer’s Disease.

Methods

In young healthy adults, we developed a learning procedure with 20 relationships and associated biographical information. We tested whether recall could be improved using TMR. On Day-1, participants learned relationships and facts about simulated family members (e.g., “Your youngest son is Clifford; Clifford is an architect”). After a short delay, they were tested on this information (e.g., “Your youngest son is___? Clifford’s occupation is___?”). On Day-2, participants learned interfering information about 10 simulated neighbors, followed by memory testing. While sleeping in their home for the next 3 nights, participants received auditory TMR cues during sleep using wearable sleep technology. Participants received either spoken questions about their simulated family (n=20, TMR group) or reversed sounds (n=20, control group). On Day-5, memory was tested again.

Results

Free recall of relationships and biographical information for the simulated family improved in the TMR group, whereas it declined in the control group (Day-5 vs. Day-1). Furthermore, recall confidence decreased less in the TMR group than in the control group (Day-5 vs. Day-1).

Conclusion

Results indicate that memory for specific information can be improved with overnight TMR sounds delivered in the home environment. The information was arbitrary person-specific knowledge that was recently acquired, but a parallel improvement may also be achievable in older individuals experiencing difficulty recalling high-value information subject to forgetting in their own lives. We are thus beginning studies in older individuals to test this possibility.

Support (if any)

Funding was provided by the National Institutes of Health (R01-NS112942 and T32-HL007909) and the National Science Foundation (BCS-2048681).
0076 Memory Consolidation During SWS of Implicit Visuospatial Memory Associated with Odor
Authors: Ahn Jungho , Takahashi Toshiharu
Published: April 2024

Introduction

Memory consolidation during sleep is more pronounced during SWS, but this effect depends on the form of learning (implicit or explicit). Also, it is considered that the piriform cortex, the primary olfactory cortex, replay and consolidates the olfactory stimuli perceived before sleep, as well as memories associated with the olfactory stimulus, during SWS. In this study, we investigated the consolidation of implicit visuospatial memory associated with olfactory stimuli during sleep in human subjects.

Methods

ROCF (Rey-Osterrieth Complex Figure) was used for the visuospatial memory task, and peppermint, liquid paraffin were used as experimental and control stimuli, respectively. Participants performed an implicit learning task in which they copied the ROCF while inhaling the experimental or control odor before nap(No instructions to memorize or test). After the learning, participants completed a baseline test in which they recalled the ROCF without inhaling the odor, and then took a 135-minute nap. After the nap, the ROCF recall test was repeated with inhaling experimental or control odor.

Results

Data from 28 of the 56 participants for whom SWS appeared were used in the statistical analysis. The analysis revealed that the slow-spindle PSD(Power Spectral Density) during SWS in the prefrontal cortex of the group that inhaled the experimental odor during ROCF learning was lower than that of the group in the control odor inhaled group. The results of linear regression analysis using prefrontal slow-spindle PSD as a moderator showed that when prefrontal slow-spindle PSD was lower than average, the memory performance (hit-rate change of ROCF) of the group that inhaled the experimental odor during ROCF learning was higher than that of the group that inhaled the control odor. This difference disappeared where the slow-spindle PSD exceeded the average.

Conclusion

Consolidation of odor associated implicit visuospatial memories during SWS was found to be associated with a decrease in prefrontal slow-spindle activity. Prefrontal slow-spindle activity during SWS is associated with the erasure of unstable memories, and olfactory cortex may suppress this activity to make unstable memories into long-lasting memories.

Support (if any)
0080 Selective Brain and Eye Responses to Auditory Stimuli During Phasic and Tonic REM Sleep
Authors: Ameen Mohamed , Topalidis Pavlos , Simor Peter , Schabus Manuel , Hoedlmoser Kerstin
Published: April 2024

Introduction

Rapid eye movement (REM) sleep is divided into phasic and tonic episodes based on the presence or absence of eye movements, respectively. Phasic REM, often linked with dreaming, is traditionally seen as a phase of brain isolation from the surroundings. On the contrary, during tonic REM periods, the brain is thought to maintain a stronger connection to the environment and a higher sensitivity to external stimuli. However, the processing of external information during these distinct REM microstates is not well-understood. Here, we aim to investigate sensory processing during REM microstates by analyzing brain and eye responses to different auditory stimuli.

Methods

We analyzed high-density electroencephalography (EEG) data from 17 healthy subjects over a full night's sleep. Auditory stimuli included the subjects' own name (SON) and two unfamiliar names (UNs), spoken by familiar (FV) and unfamiliar voices (UFV). REM sleep was categorized into one-second epochs of either phasic and tonic episodes based on rapid eye movement occurrence. Our analysis encompassed multivariate decoding, event-related and time-frequency analyses, examination of aperiodic EEG activity, and measuring the velocity of the evoked eye movement responses.

Results

Tonic REM showed more microarousals and a shallower EEG slope than phasic REM, suggesting increased external processing and more excitatory cortical activity. Further, auditory brain responses during tonic REM revealed stronger alpha (8-12 Hz) and beta (13-30 Hz) responses to responses to UFVs as compared to FVs. In contrast, during phasic REM, we observed stronger desynchronization in the delta (1-4 Hz) frequency range in response to UFVs as compared to FVs. No difference in brain responses to the different names was observed. However, eye responses to SONs were notably stronger than to UNs during phasic REM periods.

Conclusion

Our findings support existing theories that suggest a preference for unfamiliar stimuli processing during sleep. We extend previous findings by showing that such preference is perserved in REM sleep as well. We also found that eye movements in phasic REM can distinguish between sounds, indicating partial brain responsiveness to the environment during dreaming episodes. These results enhance our understanding of REM sleep's complex nature and the neural activities occurring during this intriguing sleep stage.

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0084 Differently Worded Questions Do Not Substantially Influence Subject Predictions of Performance
Authors: Hovland Sean , Hudson Amanda , Van Dongen Hans , Kurinec Courtney , Honn Kimberly
Published: April 2024

Introduction

Being able to accurately predict when one’s performance is likely to be impaired by sleep loss can help avoid costly errors. However, the literature is mixed on how accurately individuals are able to make such predictions. Subjective predictions of performance made during total sleep deprivation (TSD) are often only as accurate as judgments of subjective sleepiness, which are poorly correlated. We investigated whether the wording of a question about anticipated performance on a Psychomotor Vigilance Task (PVT) influences the ability to predict actual performance during TSD.

Methods

N=56 healthy adults (ages 25.9±5.3y, 32 females) were randomly assigned to 38h TSD in a 4-day/3-night laboratory study. The PVT and the Karolinska Sleepiness Scale (KSS) were administered approximately every 2-4h during scheduled wakefulness. We created four differently worded questions to elicit ratings of predicted performance on a scale from 1 (worse performance) to 9 (better performance). The questions asked about expected performance at the beginning or end of the PVT, expected duration of good performance, or expected time until impairment. Participants completed the KSS and answered one of the questions (randomly selected), and then performed the PVT. Using separate linear regressions with a fixed effect for rating and a random intercept over participants, we examined whether any of the questions, or the KSS ratings, were better able to predict PVT lapses (RT>500ms). Results were compared using root mean square error (RMSE), a measure of absolute model fit.

Results

Using the predictive accuracy of the KSS as a reference (RMSE=4.71), the RMSE values for the questions ranged from 10.0% lower (RMSE=4.24), indicating slightly better accuracy for predicting subsequent PVT performance, to 13.0% higher (RMSE=5.32), indicating slightly worse accuracy for predicting subsequent PVT performance.

Conclusion

Our results suggest that the wording of a question about anticipated performance on the PVT influences its predictive utility, but with no more than 10% improvement over KSS-rated subjective sleepiness as a performance predictor, the predictive gain was not substantial. This puts into question whether self-predictions of performance, regardless of how they are framed, can be relied upon for assessments of readiness in operational settings.

Support (if any)

CDMRP W81XWH-16-1-0319
0085 Dream Bizarreness Is Related to Specific Aspects of Metacognition That Are Influenced by Personality
Authors: Price Michael , Haque Zehra , Garza Lydia , Westerberg Carmen
Published: April 2024

Introduction

According to the continuity hypothesis, dreams reflect waking life experiences. Metacognition, the awareness of one’s thought processes, is minimal during typical dreaming but is assumed to be greater during lucid dreams, when the dreamer is aware they are dreaming and can sometimes control dream content. Therefore, one hypothesis is that lucid dreams may be more continuous with waking life than non-lucid dreams and thus contain less bizarre content than non-lucid dreams. However, support for this hypothesis is mixed and it may be incomplete, as metacognition typically includes multiple components, including the awareness of thinking and the regulation of processes involved in thinking. Additionally, these various metacognitive aspects may be differentially influenced by personality.

Methods

To further examine how dream bizarreness relates to metacognition, 416 participants completed a survey including measures of dreaming frequency, sleep quality, multiple aspects of metacognition, and the Big 5 personality traits. Participants also reported their most recent lucid and non-lucid dreams which were scored for bizarreness. Relationships between dream bizarreness, metacognition, and personality were subsequently assessed.

Results

Seventy-eight participants were able to report both a lucid and non-lucid dream and contributed to analyses. In contrast to the continuity hypothesis, lucid dreams were more bizarre than non-lucid dreams, and regression analyses revealed that non-lucid dream bizarreness positively predicted awareness of dream dissociation, whereas higher lucid dream bizarreness was associated with fewer negative beliefs about uncontrollability and danger. Finally, higher neuroticism and lower conscientiousness were associated with higher negative beliefs about uncontrollability and danger. No relationships between personality and dream dissociation were present.

Conclusion

The hypothesis that, due to greater metacognitive awareness, lucid dreams are less bizarre than non-lucid dreams, was not supported. Instead, bizarre non-lucid dreams may emerge with increased self-disconnection and bizarre lucid dreams may occur when worry about losing control and associated dangers therein is low. Additionally, due to the observed relationships between personality and metacognition, low neuroticism and high conscientiousness may also increase the bizarreness of lucid dreams. Collectively, these results suggest that dream bizarreness may reflect specific aspects of metacognition rather than a general awareness that one is dreaming.

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