bluuebunny/crossref_metadata_2025_split huggingface dataset:
023 Sleep in a Brainless Animal - The Relationship Between Centralization and Sleep in the Upside-down Jellyfish
Authors: Abrams Michael 
Published: May 2021

Abstract

Introduction
Though sleep is pervasive in animals, its fundamental roles, and the processes involved in generating the behavior, remain poorly understood. A key outstanding question in sleep regulation is whether sleep is controlled strictly by a top-down mechanism via activity of specific central nervous system (CNS) neurons or is controlled partially by bottom-up signals from neural and non-neural tissue. Recently, we showed that the upside-down jellyfish Cassiopea sleeps, providing an opportunity to study sleep control, regulation, and function in an animal without a CNS.

Methods
Cassiopea have a decentralized nervous system (DNS) of radially spaced interconnected ganglia called rhopalia along their bell margin that control muscle contractions. The signal to contract is sent to muscle fibers local to the initiating ganglion, and the contraction propagates outwards as a point source wave. We have developed computer programs to detect the controlling ganglion, which allows us to non-invasively determine ganglia activity, and to understand how a simple network of ganglia controls behavior. We are also using immunofluorescence, in situ hybridization, qPCR, and RNAseq to characterize the effect of sleep deprivation (SD) on the jellyfish nervous system.

Results
We have discovered a temporally centralized form of behavioral control that changes between day and night, and during SD. A subset of ganglia share behavioral control—while some almost never initiate contractions, others are active both day and night, or are mostly day-active or night-active, and SD drastically changes ganglia usage. Regions that increase activity at night are less active the following day, perhaps evidence of homeostatic regulation. Using RNAseq we found that during SD, one nAChRα subunit increases expression ~3.8-fold and we are studying its role in arousal and sleep.

Conclusion
We are investigating a different kind of nervous system, one that is morphologically decentralized (a network of discrete ganglia), and yet temporally centralized (a subset of ganglia dominate activity control). Wake, sleep, and SD involve different ganglia activity patterns, different levels of centralization, and different gene expression. Thus, temporal centralization could provide a mechanism to explain how local sleep, via a bottom-up mechanism, can result in organismal sleep behavior.

Support (if any)
UC Berkeley Miller Postdoctoral Fellowship
024 Quiescent Wakefulness: Characterising the Impact of Oxytocin on Sleep-Wake Behaviour in Male and Female Rats
Authors: Raymond Joel , Everett Nicholas , Gururajan Anand , Bowen Michael 
Published: May 2021

Abstract

Introduction
Oxytocin is a versatile hypothalamic neuropeptide involved in diverse neurobehavioural processes. Since oxytocin can elicit anxiolytic and serenic effects, one could hypothesise that oxytocin should prime the brain for sleep and promote hypnogenesis. However, based on the social salience hypothesis—that oxytocin promotes prosocial behaviour and directs attention toward social stimuli—one could also posit that oxytocin should promote wakefulness. At present, little research has comprehensively characterised the effect of oxytocin on sleep-wake behaviour and no explanation to reconcile these two seemingly competing hypotheses has been proposed.

Methods
This study investigated the effects of oxytocin on sleep-wake outcomes using radiotelemetry-based polysomnography in adult male and female Wistar rats. Oxytocin was administered via the intraperitoneal (IP; 0.1, 0.3 and 1 mg/kg) and intranasal (IN; 0.06, 1, 3 mg/kg) routes. Caffeine (IP and IN; 10 mg/kg) was also administered as a wake-promoting positive control. Additionally, pre-treatment with the oxytocin receptor (OTR) antagonist L-368,899 (IP; 5 mg/kg) and vasopressin 1a receptor (V1aR) antagonist SR49059 (IP; 1 mg/kg) followed by oxytocin (IP; 1 mg/kg) was conducted to determine which receptor(s) mediated sleep-wake effects of oxytocin.

Results
In both male and female rats, IP oxytocin produced dose-dependent effects on sleep-wake behaviour. Specifically, oxytocin initially promoted quiescent wakefulness (a restful but conscious state) at the cost of reducing both active wakefulness and sleep. Throughout the 1.5-hour period post-administration, oxytocin delayed REM sleep onset and reduced the proportion of both NREM and REM sleep. Conversely, IN oxytocin did not significantly alter any sleep-wake parameters at any dose tested. Caffeine demonstrated wake-promoting effects under both the IP and IN routes of administration. The involvement of OTR and V1aR binding in oxytocin-induced effects on sleep-wake outcomes will be discussed.

Conclusion
These findings appear to reconcile the two competing hypotheses: in rats, IP oxytocin appears to promote a state of quiescent wakefulness—one of calm and rest, but also of conscious responsivity to environmental stimuli. IN oxytocin demonstrated little to no effect on sleep-wake behaviour, which is a crucial finding given the escalating use of IN oxytocin as a therapeutic for conditions with comorbid disordered sleep.

Support (if any)
None.
027 GABAergic Neurons in the Dorsal Raphe Nucleus Are under the Influence of GABAergic Inputs from the Nucleus Pontis Oralis
Authors: Zhang Jianhua , Xi Mingchu , Fung Simon , Tobin Charles , Sampogna Sharon , Chase Michael 
Published: May 2021

Abstract

Introduction
Our previous study has shown that there is a direct connection between GABAergic neurons in the nucleus pontis oralis (NPO) and neurons of the dorsal raphe nucleus (DR), providing a morphological basis for the hypothesis that GABAergic inhibitory processes in NPO play an important role in the generation and maintenance of wakefulness as well as active (REM) sleep through the interaction with neurons in the DR. However, the target of such a GABAergic projection from the NPO within the DR is unknown. In the present study, a double-fluorescent labeling technique was employed to examine the target of GABAergic inputs to the DR.

Methods
Adult cats were deeply anesthetized and perfused transcardially. Subsequently, the brainstem containing the DR was removed, postfixed and cut into 15 μm coronal sections with a Reichert-Jung cryostat. The sections were immunostained with antibodies against GABA-A or GABA-B receptors and GABA following the procedure of double fluorescence immunohistochemistry.

Results
Under fluorescence microscopy, a large number of neurons were labeled with antibodies against either GABA-A receptor or GABA-B receptor. In addition, neurons labeled with antibody against GABA were observed in the DR. With double fluorescence immunohistochemical techniques, some neurons labeled by anti-GABA antibody were also stained with antibodies against GABA-A or GABA-B receptors.

Conclusion
The expression of GABA-A or GABA-B receptors by GABAergic neurons in the DR indicates that GABAergic neurons in the DR receive GABAergic inputs. Our previous study has demonstrated that these GABAergic inputs are from the NPO. These data provide a morphological foundation to support our hypothesis that, during wakefulness, NPO GABAergic “Executive” neurons suppress “Second-Order” GABAergic neurons in the DR, which, in turn, activate (disinhibit) serotonergic wake-on neurons in this nucleus.

Support (if any)
NS092383
031 The reduced benefit of sleep for memory trace consolidation with age
Authors: Toor Balmeet , van den Berg Nicholas , Ray Laura , Fang Lydia , Fogel Stuart 
Published: May 2021

Abstract

Introduction
Sleep is known to enhance the realization of novel solutions to problems. As we age, both the quantity and quality of sleep are reduced. Age-related deficits in sleep-dependent memory consolidation have been recently identified, however, the scope of these deficits is not. Here, we sought to investigate the behavioural and neuronal functional consequences of age-related changes in sleep for gaining insight into novel cognitive strategies (e.g., on the Tower of Hanoi; ToH).

Methods
40 healthy young adults (20–25 years), and 30 healthy older adults (60–85 years) participated, and were assigned to either the nap [young-nap (YN), older-nap (ON)] or wake [young-no-nap (YNN), older-no-nap (ONN)] conditions. Participants were trained on the ToH in the AM, followed by either a 90 minute nap opportunity or a period of wake, and were retested afterward. The ToH is a procedural task that requires the acquisition of a novel cognitive strategy (i.e., recursive logic). Alternating blocks of ToH practice and rest were performed while functional MRI scans were obtained at 3T to examine differences (pFDR&lt;0.05) in brain activation from training to retest in young vs. older groups as a function of sleep [(YN-YNN)-(ON-ONN)].

Results
Sleep significantly benefitted the young but not the older participants (speed and accuracy) on the ToH. A bilateral difference in activation of the hippocampus was observed from training to retest between young and older subjects. Specifically, YN displayed decreased activation, whereas YNN showed increased activation. The older groups showed the opposite pattern whereby ON displayed increased activation whereas ONN showed decreased activation. The same pattern was observed for the middle temporal gyrus and medial prefrontal cortex. By contrast, the opposite pattern was observed in the premotor area, inferior and superior parietal cortex.

Conclusion
These results suggest that sleep differentially contributes to the realization of a novel cognitive strategy in young vs. older individuals, consistent with the notion that as the consolidation of a newly formed memory trace progresses, the hippocampus becomes less involved over time; especially so when sleep occurs during that time. Our results suggest that sleep preferentially contributes to this process in the young, but not in older individuals.
Support (if any):
032 Sleep Consolidates Memory for Strong but not Weak Information After Incidental Encoding
Authors: Wernette Elle , Fenn Kimberly 
Published: May 2021

Abstract

Introduction
Slow wave sleep (SWS) strengthens memory for studied information, but research on the effect of sleep on information that is not intentionally remembered is scarce. Previous research from our lab suggests sleep consolidates some information that has been encoded incidentally, meaning that it has been acted on but not intentionally remembered. It remains unclear what determines which information is consolidated during sleep after incidental encoding and what aspects of sleep are related to this mnemonic benefit. In two experiments, we test the hypothesis that sleep consolidates strong but not weak memory traces following incidental encoding and assess the relationship between memory performance and sleep attributes.

Methods
In Experiment 1, we manipulated memory strength within- and between-subjects. Participants rated words one or three times (within) in a shallow or deep incidental encoding task (between). In the shallow task, participants counted vowels in each word; in the deep task, participants rated each word on a scale from ‘concrete’ to ‘abstract’. Following a 12-hour period containing sleep or wakefulness, participants took a surprise memory test. In Experiment 2, participants rated words one or three times in the deep encoding task, received an 8-hour sleep opportunity with partial PSG, and took the surprise memory test.

Results
In Experiment 1, participants remembered words better after sleep than wake regardless of number of encoding trials, but only after deep encoding. There was not an effect of sleep following shallow encoding. In Experiment 2, SWS correlated negatively with response latency for correctly recognized words encoded once, but not those encoded three times. That is, participants who received more SWS showed faster performance.

Conclusion
Results suggest sleep consolidated information based on the depth of encoding, and this benefit was related to SWS. This work is broadly consistent with theories of memory consolidation that predict sleep is more beneficial for strong than weak memory traces, such as the synaptic downscaling hypothesis.
Support (if any):
036 The Effect of Exercise on Sleep Architecture and Memory Consolidation during a Daytime Nap
Authors: Collins Megan , Wamsley Erin , Napier Hailey , Ray Madeline 
Published: May 2021

Abstract

Introduction
Slow wave sleep (SWS) is thought to especially benefit declarative memory (i.e., memory for facts and events). As such, recent studies have used various methods to experimentally increase the amount of slow wave sleep that participants obtain, with the goal of assessing how SWS affects declarative memory consolidation. Studies dating back decades have reported that exercising before sleep may increase time spent in SWS. Thus, the aim of the current project was to determine whether exercising after learning verbal information enhances slow wave sleep during a subsequent nap and/or enhances memory for verbal information.

Methods
Participants who exercised regularly were recruited to attend two 2.5hr laboratory sessions. During each session, they trained on a paired associates learning task and then completed either a 20min cardiovascular exercise routine or a 20min stretching routine. Following a 1hr nap opportunity, participants were tested on their memory. PSG was recorded during the nap, and scored following AASM criteria. Participants were excluded from analysis if they failed to sleep for at least 10 min. Following exclusions, n=30 participants were included in analysis.

Results
Contrary to our hypotheses, there was no significant difference between the exercise and stretching conditions for minutes spent in slow wave sleep (p=.16), % time spent in slow wave sleep (p=.22), or raw improvement in paired associated performance (p=.23). The amount of SWS obtained during the nap did not correlate with performance in either condition (SWS min vs. memory in exercise condition: r28=.10, p=.60; sleep condition: r28=-.06, p=.74). Exercise did not affect time spent in any other sleep stage, nor did it affect total sleep time.

Conclusion
Contrary to our hypotheses and the results of prior research, we were unable to detect a significant effect of exercise on slow wave sleep. Also contrary to our hypotheses, exercise did not affect memory retention across the nap interval. These null results could indicate that there is no effect of exercise on nap sleep and/or associated memory retention. However, it could also be that we lacked sufficient power to detect effects that were smaller than expected.
Support (if any):
040 Sleep Deprivation Disrupts Binding of Information with Its Context
Authors: Kurinec Courtney , Whitney Paul , Hinson John , Hansen Devon , Van Dongen Hans 
Published: May 2021

Abstract

Introduction
Effective memory often requires recall of both specific information and the context in which the information was encountered. Total sleep deprivation (TSD) is known to impair memory for information items (e.g., words on a studied list), but the impact of TSD on binding, or associative linking, between items and context is not clear.

Methods
N=68 healthy adults (ages 22–40; 35 females) completed a 4-day (3-night) in-laboratory study. After a baseline night with 10h nighttime sleep opportunity, participants were randomly assigned to either 38h TSD (n=38) or a well-rested control (WRC) condition with 10h nighttime sleep opportunity (n=30). Both study arms concluded with a 10h nighttime recovery sleep opportunity. Participants completed a standardized recognition memory task at 14:50 on day 2 (baseline, session 1) and again 24h later (session 2). The memory task consisted of a study phase in which words with negative, positive, and neutral affective valence were spoken by a female or male speaker (50% each); followed immediately by a test phase, in which subjects made recognition judgments for the items (words) and their source (speaker).

Results
Mixed-effects ANOVA revealed significant interactions of session by condition for both word and speaker recognition (p&lt;0.001). When sleep-deprived, TSD participants recognized fewer words and, for words that were correctly recognized, they were worse at recognizing the speaker, compared to baseline and to the WRC group. Negatively valenced words were associated with poorer word recognition (p&lt;0.001), and in session 1 poorer source recognition (p = 0.032), but these valence effects did not interact with sleep deprivation.

Conclusion
TSD impaired memory for items, but more importantly, also impaired memory for the context in which items were presented, even if the items were themselves correctly recognized, and regardless of their affective valence. These results indicate that TSD may disrupt binding of information to its context, which could explain TSD deficits in decision-making tasks that require novel associative linking. Furthermore, our findings are important in real-world situations such as eyewitness accounts and perseveration of the influence of misinformation.

Support (if any)
NIH grant R21 CA167691 and CDMRP award W81XWH-20-1-0442
044 Slow oscillatory transcranial direct current stimulation enhances cognitive performance during subsequent sleep deprivation
Authors: Hughes John , Doty Tracy Jill , Ratcliffe Ruthie , Balkin Thomas 
Published: May 2021

Abstract

Introduction
The EEG slow oscillation of &lt; 1 Hertz frequency has been implicated in various sleep functions, sparking a recent interest in slow oscillation enhancement strategies. In a seminal study, Marshall et al. (2006) demonstrated that 25 minutes of a slow oscillatory form of transcranial direct current stimulation (SO-tDCS) during early nocturnal sleep improved subsequent retention of word pairs learned prior to sleep, consistent with a proposed role for the slow oscillation in sleep-related memory consolidation. Another proposed function of the slow oscillation is synaptic downscaling, hypothesized to constitute the physiological basis for satisfying the homeostatic drive for sleep, per the synaptic homeostasis hypothesis of Tononi and Cirelli. We sought to determine if SO-tDCS could enhance the restorative properties of sleep, by enhancing slow oscillation activity, during a restricted sleep opportunity by assessing performance during a subsequent period of sleep deprivation (SD).

Methods
Twenty-six healthy volunteers were randomized into two groups. Participants either received electrical stimulation with 50 minutes of SO-tDCS at 0.75Hz, or sham stimulation, during the second hour of a restricted two hour sleep opportunity (11:00PM TO 1:00AM), followed by a 46 hour period of SD and then two recovery nights of sleep. Vigilance was assessed periodically with the Psychomotor Vigilance Test (PVT) during a baseline day, SD, and during the two days following recovery sleep nights.

Results
A mixed linear regression revealed significant main effects of day, group, and the interaction between group and day on mean reaction time (RT). Posthoc analysis revealed faster RTs following stimulation on day 2 of SD. It was also found that participants in the stimulation group had fewer major lapses (RTs &gt; 500 ms) than those in the sham group over the first three days following stimulation.

Conclusion
Slow oscillatory transcranial direct current stimulation during a portion of a restricted period of sleep appears to enhance sleep’s restorative properties and improves cognitive performance during subsequent sustained wakefulness. The mechanistic basis for this phenomenon may be increased slow oscillation induced synaptic renormalization.

Support (if any)
Department of Defense Military Operational Medicine Research Program (MOMRP)
046 Sleep-dependent prospective memory consolidation is impaired with aging
Authors: Leong Ruth , Lo June , Chee Michael 
Published: May 2021

Abstract

Introduction
Existing literature suggests that sleep-dependent memory consolidation is impaired in older adults but may be preserved for personally relevant information. Prospective memory (PM) involves remembering to execute future intentions in a timely manner and has behavioural importance. As previous work suggests that N3 sleep is important for PM in young adults, we investigated if the role of N3 sleep in PM consolidation would be maintained in older adults.

Methods
49 young adults (mean age±SD: 21.8±1.61 years) and 49 healthy older adults (mean age±SD: 65.7±6.30 years) were randomized into sleep and wake groups. After a semantic categorization task, participants encoded intentions comprising 4 related and 4 unrelated cue-action pairs. They were instructed to remember to perform these actions in response to cue words presented during a second semantic categorization task 12h later that encompassed either daytime wake (09:00-21:00) or overnight sleep with polysomnography (21:00-09:00).

Results
The significant condition x age group x relatedness interaction suggested that the sleep benefit on PM intentions varied according to age group and relatedness (p=0.01). For related intentions, sleep relative to wake benefitted young adults’ performance (p&lt;0.001) but not older adults (p=0.30). For unrelated intentions, sleep did not improve PM for either age group. While post-encoding N3 was significantly associated with related intentions’ execution in young adults (r=0.43, p=0.02), this relationship was not found for older adults (r=-0.07, p=0.763).

Conclusion
The age-related impairment of sleep-dependent memory consolidation extends to prospective memory. Our findings add to an existing body of work suggesting that the link between sleep and memory is functionally weakened in older adulthood.

Support (if any)
This work was supported by the National Medical Research Council, Singapore (NMRC/STaR/015/2013) and the National Research Foundation, Singapore (NRF2016_SOL002).