Cognitive consequences of sleep and sleep loss

Work Shift and Circadian Rhythm as Risk Factors for Poor Sleep Quality in Public Workers from Murcia (Spain)

The purpose of this study was to determine the prevalence of sleep quality and to investigate variables predicting the risk of poor sleep quality in public workers from Murcia (Spain). A cross-sectional and prospective study was conducted from October 2013 to February 2016 in 476 public workers. The Pittsburgh Sleep Quality Index was used to measure the quality of sleep, and the reduced scale of the Horne and Österberg Morningness-Eveningness Questionnaire was applied to analyze the circadian typology. The predictive variables of self-reported poor sleep quality were identified by multivariate logistic regression. No significant differences were found according to sex in the overall sleep quality scores (5 ± 2.9 versus 5.1 ± 3, p = 0.650), but there were in the duration of sleep. Three percent of females slept <5 hours compared to 2% of men (p = 0.034). Fixed morning shifts (OR = 1.9, 95% CI 1.3-3.1; p = 0.007) and evening chronotypes (OR = 1.6, 95% CI 1.0-2.3; p = 0.017) were independent predictors of suffering from poor sleep quality. In conclusion, the frequency of self-reported poor sleep quality among public workers from Murcia was 37.4%. Being a public worker with a fixed morning shift and having an evening chronotype demonstrated to be associated with the quality of sleep.

The spleen mediates chronic sleep restriction-mediated enhancement of LPS-induced neuroinflammation, cognitive deficits, and anxiety-like behavior

Chronic sleep restriction promotes neuroinflammation and cognitive deficits in neurodegenerative and neurobehavioral diseases. The spleens of mice exposed to chronic and repeated psychological stress serve as a reservoir of inflammatory myeloid cells that are released into the blood and brain following secondary acute stress. Here, we tested whether chronic and repeated short-term sleep restriction (CRSR) would exacerbate lipopolysaccharide (LPS)-induced neuroinflammation, cognitive deficits, and anxiety-like behavior in a spleen-dependent manner. LPS was administered to aged mice 14 days after exposure to CRSR consisting of three cycles of 7 days of sleep restriction with 7-day intervals in between. CRSR increased plasma proinflammatory cytokine levels, blood-brain barrier permeability, hippocampal proinflammatory cytokine levels, and transition of microglia to the M1 phenotype 24 h after LPS treatment. This in turn led to cognitive deficits and anxiety-like behavior. Interestingly, removal of the spleen 14 days prior to CRSR abrogated the enhancement of LPS-induced increases in systemic inflammation, neuroinflammation, cognitive deficits, and anxiety-like behavior. These data indicate that the spleen was essential for CRSR-induced exacerbation of LPS-induced brain damage.

Health behaviour changes during COVID-19 and the potential consequences: A mini-review

The COVID-19 pandemic has brought about profound changes to social behaviour. While calls to identify mental health effects that may stem from these changes should be heeded, there is also a need to examine potential changes with respect to health behaviours. Media reports have signalled dramatic shifts in sleep, substance use, physical activity and diet, which may have subsequent downstream mental health consequences. We briefly discuss the interplay between health behaviours and mental health, and the possible changes in these areas resulting from anti-pandemic measures. We also highlight a call for greater research efforts to address the short and long-term consequences of changes to health behaviours.

Physical Effects of Maternal Deaths on Midwives' Health: A Qualitative Approach

Grief does not only affect human emotions but also impacts their physical health. Understanding physical grief of people can bring to bear the grip of its daunting nature, a situation where routines become challenging. A qualitative explorative descriptive research method was used. A purposive sample of 18 ward supervisors and 39 ward midwives was used to ascertain the physical effects of maternal deaths on these caregivers in the Ashanti Region of Ghana. Data were collected through semistructured and focus group discussions. Data analysis was done parallel with data collection till saturation was reached. Ethics was obtained from the University of the Western Cape, South Africa, and Ghana Health Service. The findings indicated that generally, as a result of grieving over the deaths of their patients, midwives experienced physical health sufferings. Therefore, reported depression is expressed as insomnia, appetite loss, exhaustion, and social isolation. There is the need to reduce the physical effects of patients' death on caregivers in Ghana and therefore, the study recommends that all hospitals in Ghana utilize employee assistance programmes, a workplace intervention programme designed for such purposes.

Inflammation and the dimensions of depression: A review

Patients with depressive disorders show a wide range of clinical manifestations including cognitive and neurovegetative symptoms. Importantly, these symptoms can differ in terms of biological etiology, and deconstructing depression into specific symptoms may provide valuable insight into the underlying neurobiology. Little research has examined inflammation in the context of depressive dimensions. Here we conduct a narrative review of the existing literature (21 studies) to elucidate whether the depression-inflammation link is symptom specific. Overall, there is evidence that an association exists between neurovegetative symptoms of depression and inflammation, independent of cognitive symptoms. The same cannot be said of cognitive symptoms and inflammation. There is also some evidence of gender differences in the directionality of the relationship between depression and inflammation. Potential explanations for these findings, limitations of the existing literature and recommendations for future research design are discussed.

Neurological dysfunction after cardiac surgery and cardiac intensive care admission: A narrative review part 2: Cognitive dysfunction after critical illness; potential contributors in surgery and intensive care; pathogenesis; and therapies to prevent/treat perioperative neurological dysfunction

Severe cognitive decline and cognitive dysfunction has been attributed to patient's stay in the cardiovascular intensive care unit. Prolonged mechanical ventilation, long duration of stay, sedation protocols, and sleep deprivation contribute to patients developing neurocognitive disorder after intensive care admission and it is associated with poor clinical outcomes. Trauma of surgery, stress of critical care, and administration of anaesthesia evoke a systemic inflammatory response and trigger neuroinflammation and oxidative stress. Anaesthetic agents modulate the function of the GABA receptors. The persistence of these effects in the postoperative period promotes development of cognitive dysfunction. A number of drugs are under investigation to restrict or prevent this cognitive decline.

Protective effects of Hydrocotyle umbellata var. bonariensis Lam. (Araliaceae) on memory in sleep-impaired female mice

ETHNOPHARMACOLOGICAL RELEVANCE

Hydrocotyle umbellata var.bonariensis Lam. (Hb), popularly known in Brazil as acariçoba and outside Brazil Hb by a number of names including marsh-pennywort, and many-flower, has traditionally been used in Ayurvedic medicine in the retardation of aging (Rasayana effect).

AIM OF THE STUDY

The present study evaluated the effect of Hb treatment before and during paradoxical sleep deprivation (PSD) and sleep restriction (SR) on learning, memory, and acetylcholinesterase (AChE) brain activity.

MATERIAL AND METHODS

Adult Swiss nulliparous female mice were randomly distributed among the experimental groups. The treated groups received the aqueous solution of Hb leaves orally at concentrations of 500 and 1.000 mg/kg. PSD and SR were induced by the multiple platform method, in which the animals remained for 3-days in PSD or 15-days in SR for 22 h per day. The collection of the vaginal epithelium occurred daily to determine the estrous cycle. Body mass gain was determined. The animals were submitted to the passive avoidance test and were then euthanized for the collection of brain tissue and the determination of cerebral cholinesterase activity.

RESULTS

The aqueous solution of Hb was associated with a significant reduction in cholinesterase activity at both doses in the SR model, and at the dose of 1.000 mg/kg in the PSD model. Regarding the learning and memory test, the PSD group treated with 1.000 mg/kg presented significant improvement, whereas in the SR experiment none of the treated-groups showed any improvement in learning and memory. In the analysis of SR/PSD interference and/or Hb treatment on the estrous cycle, it was possible to observe that the treatment acted as a protector in the SR group, maintaining a normal cycle.

CONCLUSIONS

The analyses showed that Hb was safe to use during periods of SR or PSD, acting as an adaptogen for these situations, in addition to being able to reduce cholinesterase activity, which suggests its neuroprotective action. In relation to the estrous cycle, Hb can act as a protector in SR situations.

Possible Effect of Binaural Beat Combined With Autonomous Sensory Meridian Response for Inducing Sleep

Sleep is important to maintain physical and cognitive functions in everyday life. However, the prevalence of sleep disorders is on the rise. One existing solution to this problem is to induce sleep using an auditory stimulus. When we listen to acoustic beats of two tones in each ear simultaneously, a binaural beat is generated which induces brain signals at a specific desired frequency. However, this auditory stimulus is uncomfortable for users to listen to induce sleep. To overcome this difficulty, we can exploit the feelings of calmness and relaxation that are induced by the perceptual phenomenon of autonomous sensory meridian response (ASMR). In this study, we proposed a novel auditory stimulus for inducing sleep. Specifically, we used a 6 Hz binaural beat corresponding to the center of the theta band (4-8 Hz), which is the frequency at which brain activity is entrained during non-rapid eye movement (NREM) in sleep stage 1. In addition, the "ASMR triggers" that cause ASMR were presented from natural sound as the sensory stimuli. In session 1, we combined two auditory stimuli (the 6 Hz binaural beat and ASMR triggers) at three-decibel ratios to find the optimal combination ratio. As a result, we determined that the combination of a 30:60 dB ratio of binaural beat to ASMR trigger is most effective for inducing theta power and psychological stability. In session 2, the effects of these combined stimuli (CS) were compared with an only binaural beat, only the ASMR trigger, or a sham condition. The combination stimulus retained the advantages of the binaural beat and resolved its shortcomings with the ASMR triggers, including psychological self-reports. Our findings indicate that the proposed auditory stimulus could induce the brain signals required for sleep, while simultaneously keeping the user in a psychologically comfortable state. This technology provides an important opportunity to develop a novel method for increasing the quality of sleep.

One night of sleep deprivation impairs executive function but does not affect psychomotor or motor performance

The current study assessed the impact of one night of sleep deprivation on cognitive, motor and psychomotor performance. Thirty healthy young adult male subjects completed a 24 h control or 24 h sleep deprived trial. For the control trial, participants (N = 15) were allowed normal night sleep (~8 h). For the sleep deprived trial, participants (N = 15) did not sleep for 24 h. Cognitive performance during go/no-go, Stroop and simple reaction tasks, psychomotor performance during speed-accuracy tasks with fixed and unfixed targets, and motor performance during countermovement jump, hand grip strength, and 30-s maximal voluntary contraction tasks were evaluated on day 1 at 8 am and 7 pm and on day 2 at 8 am. One night of sleep deprivation impaired psychological well-being and executive function but did not affect simple reaction time, the capacity for arm and leg muscle contraction, motor control performance during a speed–accuracy task with both fixed and unfixed targets, and central and peripheral motor fatigue in the 30 s maximal voluntary contraction task. The present study showed that one night of sleep deprivation resulted in executive function deterioration but did not modify motor control or maximal effort requiring performance of motor tasks.

Sleep as a topic in nursing education programs? A mixed method study of syllabuses and nursing students' perceptions

BACKGROUND

Sleep is a basic human need and is considered important for maintaining health. It is even more important during illness due to its impact for example on our immune system. Nurses have an important role in identifying sleep deprivation. They are also in a unique position to promote and address sleep among patients. However, it is essential that they are provided with the appropriate knowledge during training.

AIM

To explore and describe nursing students' perceptions of preparedness to adress and support patients' sleep during hospitalization and to apply sleep-promoting interventions in a clinical context. Furthermore, the aim was to investigate if, and how, the topic of sleep is explicitly incorporated in nursing education programs.

DESIGN

A descriptive study based on a mixed method approach.

METHODS

Quantitative and qualitative data were collected from program and course syllabuses and intended learning outcomes from three universities. Twenty-one nursing students from the same universities were interviewed during their final year of education.

RESULTS

The results of both quantitative and qualitative data consistently show that education regarding sleep and patients' sleep is limited and, in some respects, absent in the Bachelor of Science Nursing programs investigated.

CONCLUSION

This study indicates that education about sleep and patients' sleep in the nursing programs studied is insufficient and limited. This gap in knowledge may lead to prospective registered nurses using their own experiences instead of evidence-based knowledge when assessing, supporting and applying sleep-promoting interventions.

Insomnia symptoms, cannabis protective behavioral strategies, and hazardous cannabis use among U.S. college students

Previous research has reported that sleep problems longitudinally predict both onset of cannabis use and cannabis-related problems. However, the mediators of this relationship remain unclear. The present study examined (a) the concurrent relationship between insomnia symptoms and hazardous cannabis use and (b) examined whether use of protective behavioral strategies (PBS) for cannabis mediated this relationship among college student cannabis users. Participants were 984 (69.9% female) college students who reported consuming cannabis at least once in the past month and completed measures of insomnia, cannabis PBS, and cannabis misuse. Data were analyzed by structural equation modeling for binary and count outcomes. The significance of the mediator was evaluated using bias-corrected bootstrap confidence intervals. Insomnia symptoms were associated with an increase in the odds of hazardous cannabis use and possible cannabis use disorder. Cannabis PBS significantly mediated the relationship between insomnia symptoms and hazardous cannabis use, cannabis use disorder symptoms, and cannabis-related problems. Specifically, higher reports of insomnia symptoms were associated with lower use of cannabis PBS; which in turn was associated with an increase in the odds of hazardous cannabis use and possible cannabis use disorder, as well as a higher report of cannabis-related problems. Implications of these findings on the prevention of cannabis use problems among college students in the United States were discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Melatonin receptor agonist Piper betle L. ameliorates dexamethasone-induced early life stress in adult zebrafish

Early life exposure to stress has been suggested to be a crucial factor for the development of the brain and its functions. It is well documented that childhood stress is a risk factor for sleep problems in adulthood. Piper betle L. leaf extract (PB) has been used in several traditional medicines to cure various ailments. Recently, PB has been proved to have antidepressant activity. The literature suggests that antidepressants affect the synthesis and release of melatonin through several mechanisms. Thus, this study investigated the potential role of PB for the treatment of sleep disruption after early life stress exposure. Firstly, dexamethasone (DEX) (2 and 20 mg/l for 24 h) was administered to zebrafish larvae on the 4th day post-fertilization (dpf) to induce early life stress. The effects of stress on behaviour during adulthood, melatonin level and stress-related gene expression (nfkb) in the brain were then studied. Next, the possible role of PB (10 and 30 mg/Kg) was studied by measuring its effect on behaviour and by quantifying the expression levels of several melatonin-related (MT1, MT2, aanat1, aanat2) and stress-related (nfkb) genes by qPCR. DEX-treated zebrafish exhibited anxious behaviour, along with a lower level of melatonin and a higher mRNA expression of nfkb. After treatment with PB, a similar effect on behaviour and gene expression levels as the melatonin treatment group (10 mg/kg; positive control) was seen in adult zebrafish. These molecular confirmations of the observed behavioural effects of the PB indicate a possible role in the treatment of early life stress-induced sleep disruption.

Cognitive dysfunction in individuals with cocaine use disorder: Potential moderating factors and pharmacological treatments

It is well-documented in the literature that individuals repeatedly exposed to cocaine exhibit cognitive impairment and that cognitive dysfunction is a risk factor for poor treatment outcomes in those with cocaine use disorder (CUD). Specific deficits related to attention, episodic memory, working memory, and executive functioning are the most common deficits noted in this population. Given that cognitive impairment is a risk factor for poor treatment outcomes in those with CUD, identifying possible moderating factors contributing to and/or exacerbating cocaine-related cognitive deficits is of great importance. Some of these factors may include premorbid intellectual functioning, cocaine use patterns, polysubstance use, comorbid emotional symptoms, and sleep dysfunction. It is plausible that by identifying moderating factors impacting cognition, behavioral interventions can then be modified accordingly and/or treatment regimens can be augmented with pharmacological interventions (e.g., cognitive enhancing agents), leading to a reduction in treatment attrition and improved treatment outcomes. The currently available treatments for CUD are mainly behavioral with variable efficacy, and even though there have been great preclinical and clinical research efforts focused on medication development for CUD, there are currently no Food and Drug Administration-approved medications for CUD. A description of some of the several potential moderating factors, along with some pharmacological treatments which have been shown to ameliorate, at least to some extent, cognitive dysfunction in those with CUD are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The relationships between self-efficacy, self-control, chronotype, procrastination and sleep problems in young adults

The main aim of our study was to examine whether there was a relationship between psychological characteristics such as self-efficacy, self-control and chronotype as well as procrastination on the one hand and sleep problems on the other. There were 315 young adults aged between 18 and 27 years (M = 20.57). We used the General Procrastination Scale, the General Self-Efficacy Scale (GSES), Brief Self-Control Scale, the Composite Scale of Morningness (CSM) and the Pittsburgh Sleep Quality Index (PSQI). Our results indicated that low self-efficacy, low self-control and eveningness were positive predictors of procrastination. The reciprocal relationship exists between procrastination and sleep problems. Procrastination positively contributed to sleep problems, whereas sleep problems were a negative predictor of procrastination.

Prevalence and severity of sleep difficulty in patients with a CNS cancer receiving palliative care in Australia

Background

The literature describing the incidence of sleep difficulty in CNS cancers is very limited, with exploration of a sleep difficulty symptom trajectory particularly sparse in people with advanced disease. We aimed to establish the prevalence and longitudinal trajectory of sleep difficulty in populations with CNS cancers receiving palliative care nationally, and to identify clinically modifiable predictors of sleep difficulty.

Methods

A consecutive cohort of 2406 patients with CNS cancers receiving palliative care from sites participating in the Australian national Palliative Care Outcomes Collaboration were evaluated longitudinally on patient-reported sleep difficulty from point-of-care data collection, comorbid symptoms, and clinician-rated problems. Multilevel models were used to analyze patient-reported sleep difficulty.

Results

Reporting of mild to severe sleep difficulties ranged from 10% to 43%. Sleep scores fluctuated greatly over the course of palliative care. While improvement in patients' clinical status was associated with less sleep difficulty, the relationship was not clear when patients deteriorated. Worsening of sleep difficulty was associated with higher psychological distress (P < .0001), greater breathing problems (P < .05) and pain (P < .05), and higher functional status (P < .001) at the beginning of care.

Conclusions

Sleep difficulty is prevalent but fluctuates widely in patients with CNS cancers receiving palliative care. A better-tailored sleep symptom assessment may be needed for this patient population. Early interventions targeting psychological distress, breathing symptoms, and pain for more functional patients should be explored to see whether it reduces sleep difficulties late in life.

Sex differences in sleep and sleep loss-induced cognitive deficits: The influence of gonadal hormones

Males and females can respond differentially to the same environmental stimuli and experimental conditions. Chronic sleep loss is a frequent and growing problem in many modern societies and has a broad variety of negative outcomes for health and well-being. While much has been done to explore the deleterious effects of sleep deprivation (SD) on cognition in both human and animal studies over the last few decades, very little attention has been paid to the part played by sex differences and gonadal steroids in respect of changes in cognitive functions caused by sleep loss. The effects of gonadal hormones on sleep regulation and cognitive performances are well established. Reduced gonadal function in menopausal women and elderly men is associated with sleep disturbances and cognitive decline as well as dementia, which suggests that sex steroids play a key role in modulating these conditions. Finding out whether there are sex differences in respect of the effect of insufficient sleep on cognition, and how neuroendocrine mediators influence cognitive impairment induced by SD could provide valuable insights into the best therapies for each sex. In this review, we aim to highlight the involvement of sex differences and gonadal hormone status on the severity of cognitive deficits induced by sleep deficiency in both human and animal studies.

The effect of smartphone usage at bedtime on sleep quality among Saudi non- medical staff at King Saud University Medical City

Objective:

This study's main objectives are to examine the prevalence of smartphone usage at bedtime and its effect on sleep quality among Saudi non-medical staff working in King Saud University medical city in Riyadh, Saudi Arabia.

Methods:

This cross-sectional study was carried out over the period from January 2016 to July 2016 A sample of 435 Saudi adults aged 21 years and above working in King Saud University Medical City in Riyadh, Saudi Arabia participated in a self-reported Arabic questionnaire about bedtime usage of smartphone and sleep quality. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). Data were analyzed using odds ratio.

Results:

More than 98% of the respondents owned a smartphone, and nine out of ten use their smartphones at bedtime. Social media was the most used service among participants. An increase in bedtime smartphone use specially more than 60 minutes makes participants at great risk of having poor sleep quality.

Conclusion:

our findings suggest that employees who use their smartphones more at bedtime have more risk of being poor sleepers. More attention should be drawn to the misuse of smartphones and its effect sleep quality, health and productivity of adults.

Effects of Chronic Intractable Insomnia on Inflammatory Cytokines, Blood Pressure Characteristics, and Antihypertensive Efficacy in Hypertensive Patients

BACKGROUND This study investigated the changes in blood pressure and inflammatory cytokines in patients with chronic intractable insomnia, and explored the effects of chronic intractable insomnia on antihypertensive efficacy. MATERIAL AND METHODS A total of 248 patients with hypertension admitted to our hospital from 2008 to 2017 were enrolled. We enrolled 124 patients without chronic insomnia in the control group, while 124 patients with chronic insomnia were included in the treatment group. The treatment group received estazolam and was further subdivided into the effective group (n=96) and the ineffective group (n=28) according to Sleep Dysfunction Rating Scale (SDRS) scores. Sleep quality before and after treatment was determined. RESULTS Antihypertensive treatment with eplerenone (50 mg) significantly reduced SDRS scores, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), serum intercellular adhesion molecules (sICAM), and IL-1β levels, as well as systolic blood pressures (SBP) and diastolic blood pressures (DBP), with elevation of non-dipper blood pressure rhythm (P<0.05). The inhibition of intractable insomnia significantly downregulated SBP and DBP, as well as serum inflammatory cytokines such as CRP and TNF-α, showing a favorable effect on antihypertensive function. CONCLUSIONS Alleviation of chronic intractable insomnia facilitates hypertension therapy through decreasing levels of inflammatory cytokines and the proportion of non-dipper blood pressure rhythm, which offers insights for the treatment of hypertension.

Circadian Rest-Activity Rhythms Predict Cognitive Function in Early Parkinson's Disease Independently of Sleep

BACKGROUND

Cognitive impairment is a common and debilitating symptom of Parkinson's disease (PD), and its etiology is likely multifactorial. One candidate mechanism is circadian disruption. Although there is evidence of circadian abnormalities in PD, no studies have directly assessed their association with cognitive impairment.

OBJECTIVES

Investigate whether circadian rest-activity rhythm is associated with cognitive function in PD independently of sleep.

METHODS

Thirty-five participants with PD wore wrist actigraph monitors and completed sleep diaries for 7 to 10 days, then underwent neuropsychological testing. Rest-activity rhythm was characterized using nonparametric circadian rhythm analysis of actigraphy data. Objective sleep parameters were also estimated using actigraphy data. Hierarchical regression models assessed the independent contributions of sleep and rest-activity rhythm to cognitive performance.

RESULTS

Less stable day-to-day rest-activity rhythm was associated with poorer executive, visuospatial, and psychomotor functioning, but not with memory. Hierarchical regressions showed that interdaily stability's contribution to cognitive performance was independent of sleep's contributions. Whereas sleep contributed to executive function, but not psychomotor or visuospatial performance, rest-activity rhythm stability significantly contributed to variance in all three of these domains, uniquely accounting for 14.4% to 17.6% of their performance variance.

CONCLUSIONS

Our findings indicate that circadian rest-activity rhythm is associated with cognitive impairment independently of sleep. This suggests the possible utility of rest-activity rhythm as a biomarker for circadian function in PD. Future research should explore interventions to stabilize behavioral rhythms in order to strengthen circadian function, which, in turn, may reduce cognitive impairment in PD.

Sleep-dependent enhancement of emotional memory in early childhood

Naps in early childhood support declarative memory consolidation. However, emotional memories are unique in the neural basis of encoding as well as the sleep physiology underlying consolidation. Specifically, while consolidation of declarative memories has been associated with slow wave sleep, a prevailing theory suggests that REM sleep is necessary for consolidation of memories with emotional valence. Thus, we presented children (34-64 months) with faces paired with mean or nice descriptions. There were no significant main effects of emotional valence on recognition memory. Change in memory accuracy also did not differ when probed after a nap compared to the change in memory accuracy after an interval awake. However, when memory was probed again following overnight sleep, the change in memory accuracy was greater if the child napped the previous day. Greater nap slow wave activity was associated with greater memory decay during the nap. Yet nap slow wave activity also predicted greater overnight improvement in memory. These results suggest that sleep bouts can interact to benefit memory in early childhood.

Sleep disturbance of adults with a brain tumor and their family caregivers: a systematic review

The high incidence and psychophysiological morbidities of sleep disturbance in cancer have been increasingly recognized. Yet, more detailed understanding of sleep disturbance and options for management have been neglected areas in both clinical care and research. Brain tumor patients have been particularly overlooked. A systematic search of the literature from 1990 to 2015 was performed to review sleep disturbance in adults with primary or secondary brain tumor and their family caregivers. Fifty eligible studies were identified, of which 12 focused on sleep, 37 reported sleep items within a health-related quality of life measure and 1 reported caregivers' sleep. No sleep intervention has been developed or tested for brain tumor patients. Sleep disturbance and somnolence were frequently reported as the most severely rated symptoms within health-related quality of life across the disease course or treatments, along with fatigue. However, sleep-focused studies yielded inconsistent results in small samples of mostly benign brain tumors in long-term remission from total tumor resection. The research using standardized, multifaceted sleep assessments, particularly in patients with malignant brain tumor and caregivers who are undergoing treatment, is seriously lacking. A more systematic examination of sleep disturbance is warranted to inform the development of better symptom management programs in this population.

Neighborhoods, sleep quality, and cognitive decline: Does where you live and how well you sleep matter?

INTRODUCTION

We evaluated the association between neighborhood socioeconomic status (NSES) and sleep quality on cognitive decline in the Health and Retirement Study.

METHODS

Health and Retirement Study participants (n = 8090), aged 65+ with DNA and multiple biennial cognitive observations (abbreviated Telephone Interview for Cognitive Status), were included. Participants were grouped into quartiles of NSES and sleep quality scores. We adjusted for apolipoprotein E ε4, demographic, and cardiovascular risk factors. Random effects modeling evaluated cognitive change over time.

RESULTS

NSES and sleep were significantly associated with cognitive decline, and there was a significant interaction between them (P = .02). Significant differences between high/low NSES and high/low sleep quality (P < .0001) were found.

DISCUSSION

Sleep and NSES were associated with cognitive decline; the association between sleep and cognition appeared stronger among those with low NSES. The association between low NSES, poor sleep quality, and cognitive decline was roughly equivalent to the association between apolipoprotein E ε4 and cognitive decline.

A brief period of sleep deprivation causes spine loss in the dentate gyrus of mice

Sleep and sleep loss have a profound impact on hippocampal function, leading to memory impairments. Modifications in the strength of synaptic connections directly influences neuronal communication, which is vital for normal brain function, as well as the processing and storage of information. In a recently published study, we found that as little as five hours of sleep deprivation impaired hippocampus-dependent memory consolidation, which was accompanied by a reduction in dendritic spine numbers in hippocampal area CA1. Surprisingly, loss of sleep did not alter the spine density of CA3 neurons. Although sleep deprivation has been reported to affect the function of the dentate gyrus, it is unclear whether a brief period of sleep deprivation impacts spine density in this region. Here, we investigated the impact of a brief period of sleep deprivation on dendritic structure in the dentate gyrus of the dorsal hippocampus. We found that five hours of sleep loss reduces spine density in the dentate gyrus with a prominent effect on branched spines. Interestingly, the inferior blade of the dentate gyrus seems to be more vulnerable in terms of spine loss than the superior blade. This decrease in spine density predominantly in the inferior blade of the dentate gyrus may contribute to the memory deficits observed after sleep loss, as structural reorganization of synaptic networks in this subregion is fundamental for cognitive processes.

The Relationship Between Sleep and Cognition in Children Referred for Neuropsychological Evaluation: A Latent Modeling Approach

Children with conditions affecting cognitive processes experience high levels of sleep disturbance, which may further compound the cognitive ramifications of their disorders. Despite this, existing studies in this area have been primarily confined to only particular diagnostic groups and/or a limited scope of sleep and cognitive parameters. The current study characterized the nature of sleep problems and examined the relationship between a wide range of sleep-related problems and cognitive functioning in a large (N = 103) diagnostically heterogeneous sample of youth (aged 6–16) referred for neuropsychological assessment. Structural equation modeling was used to examine the relationship between sleep-related problems (i.e., daytime sleepiness, sleep onset latency, sleep fragmentation, sleep time variability, sleep debt) and cognitive performance (i.e., executive functioning, sustained attention, memory, processing speed). Sleep fragmentation emerged as the most prominent sleep-related problem in the present sample. Structural equation modeling demonstrated a negative association between sleep-related problems and cognition that did not reach statistical significance (β = −0.084, p = 0.629). The current statistical approach may be used as a conceptual framework for future work examining these multi-dimensional constructs in a parsimonious fashion.

Ovarian hormones, sleep and cognition across the adult female lifespan: An integrated perspective

Loss of ovarian function in women is associated with sleep disturbances and cognitive decline, which suggest a key role for estrogens and/or progestins in modulating these symptoms. The effects of ovarian hormones on sleep and cognitive processes have been studied in separate research fields that seldom intersect. However, sleep has a considerable impact on cognitive function. Given the tight connections between sleep and cognition, ovarian hormones may influence selective aspects of cognition indirectly, via the modulation of sleep. In support of this hypothesis, a growing body of evidence indicates that the development of sleep disorders following menopause contributes to accelerated cognitive decline and dementia in older women. This paper draws from both the animal and human literature to present an integrated view of the effects of ovarian hormones on sleep and cognition across the adult female lifespan.

Mammary Tumors Induce Central Pro-inflammatory Cytokine Expression, but Not Behavioral Deficits in Balb/C Mice

Breast cancer survivors are more likely to develop mood disorders and cognitive deficits than women in the general population. Previous studies suggest that peripheral tumors elicit central pro-inflammatory cytokine production, in turn leading to depression and cognitive deficits. In the current study, two cohorts of female Balb/C mice received bilateral orthotopic injections of syngeneic 67NR, 4T07, or 4T1cells (1 × 105 cells per injection) to induce mammary tumors. Approximately three weeks later, learned fear (via fear conditioning) or depressive-like behavior (via tail suspension and forced swim test) was assessed. Proinflammatory cytokine levels were increased in the serum (IL-1β, TNFα, IFNγ) and livers (IL-1β, IL-6, TNFα) of mice with 4T07 or 4T1 tumors compared to 67NR tumors and the vehicle control. IL-1β was increased in both the hippocampus and cortex of mice injected with 4T07 or 4T1 cell lines relative to the other treatment groups. However, mammary tumors had no effect on hippocampal doublecortin + and did not alter depressive-like behavior or learned fear. These data demonstrate that similarly sized tumors can produce differential immune responses and that tumor-induced central pro-inflammatory cytokine production can exist in the absence of depressive-like behavior or cognitive deficits.

Chronic sleep restriction promotes brain inflammation and synapse loss, and potentiates memory impairment induced by amyloid-β oligomers in mice

It is increasingly recognized that sleep disturbances and Alzheimer's disease (AD) share a bidirectional relationship. AD patients exhibit sleep problems and alterations in the regulation of circadian rhythms; conversely, poor quality of sleep increases the risk of development of AD. The aim of the current study was to determine whether chronic sleep restriction potentiates the brain impact of amyloid-β oligomers (AβOs), toxins that build up in AD brains and are thought to underlie synapse damage and memory impairment. We further investigated whether alterations in levels of pro-inflammatory mediators could play a role in memory impairment in sleep-restricted mice. We found that a single intracerebroventricular (i.c.v.) infusion of AβOs disturbed sleep pattern in mice. Conversely, chronically sleep-restricted mice exhibited higher brain expression of pro-inflammatory mediators, reductions in levels of pre- and post-synaptic marker proteins, and exhibited increased susceptibility to the impact of i.c.v. infusion of a sub-toxic dose of AβOs (1pmol) on performance in the novel object recognition memory task. Sleep-restricted mice further exhibited an increase in brain TNF-α levels in response to AβOs. Interestingly, memory impairment in sleep-restricted AβO-infused mice was prevented by treatment with the TNF-α neutralizing monoclonal antibody, infliximab. Results substantiate the notion of a dual relationship between sleep and AD, whereby AβOs disrupt sleep/wake patterns and chronic sleep restriction increases brain vulnerability to AβOs, and point to a key role of brain inflammation in increased susceptibility to AβOs in sleep-restricted mice.

The neurocognitive consequences of sleep restriction: A meta-analytic review

The current meta-analytic review evaluated the effects of experimentally manipulated sleep restriction on neurocognitive functioning. Random-effects models were employed to estimate the overall effect size and the differential effect size across cognitive domains. Age, time of day, age-adjusted sleep deficit, cumulative days of restricted sleep, sleep latency, subjective sleepiness, and biological sex were examined as potential moderators of the effect. Based on a sample of 61 studies, from 71 different populations, findings revealed a significant negative effect of sleep restriction on cognitive processing across cognitive domains (g=-0.383, p<0.001). This effect held for executive functioning (g=-0.324, p<0.001), sustained attention (g=-0.409, p<0.001), and long-term memory (g=-0.192, p=0.002). There was insufficient evidence to detect an effect within the domains of attention, multitask, impulsive decision-making or intelligence. Age group, time of day, cumulative days of restricted sleep, sleep latency, subjective sleepiness, and biological sex were all significant moderators of the overall effect. In conclusion, the current meta-analysis is the first comprehensive review to provide evidence that short-term sleep restriction significantly impairs waking neurocognitive functioning.

The Feasibility and Utility of Continuous Sleep Monitoring in Critically Ill Patients Using a Portable Electroencephalography Monitor

BACKGROUND

Sleep disruption in critically ill adults can result in acute decrements in cognitive function, including delirium, but it is underdiagnosed in the setting of the intensive care unit (ICU). Although sleep stages can be assessed by polysomnography (PSG), acquisition and interpretation of PSG is costly, is labor intensive, is difficult to do over an extended period of time with critically ill patients (multiple days of continuous recording), and may interfere with patient care. In this pilot study, we investigated the feasibility and utility of monitoring sleep in the ICU setting using a portable electroencephalography (EEG) monitor, the SedLine brain monitor.

METHODS

We first performed a baseline comparison study of the SedLine brain monitor by comparing its recordings to PSG recorded in a sleep laboratory (n = 3). In a separate patient cohort, we enrolled patients in the ICU who were monitored continuously with the SedLine monitor for sleep disruption (n = 23). In all enrolled patients, we continuously monitored their EEG. The raw EEG was retrieved and sleep stages and arousals were analyzed by a board-certified technologist. Delirium was measured by a trained research nurse using the Confusion Assessment Method developed for the ICU.

RESULTS

For all enrolled patients, we continuously monitored their EEGs and were able to retrieve the raw EEGs for analysis of sleep stages. Overall, the SedLine brain monitor was able to differentiate sleep stages, as well as capture arousals and transitions between sleep stages compared with the PSG performed in the sleep laboratory. The percentage agreement was 67% for the wake stage, 77% for the non-rapid eye movement (REM) stage (N1 = 29%, N2 = 88%, and N3 = 6%), and 89% for the REM stage. The overall agreement was measured with the use of weighted kappa, which was 0.61, 95% confidence interval, 0.58 to 0.64. In the ICU study, the mean recording time for the 23 enrolled patients was 19.10 hours. There were several signs indicative of poor-quality sleep, where sleep was distributed throughout the day, with reduced time spent in REM (1.38% ± 2.74% of total sleep time), and stage N3 (2.17% ± 5.53% of total sleep time) coupled with a high arousal index (34.63 ± 19.04 arousals per hour). The occurrence of ICU delirium was not significantly different between patients with and without sleep disruption.

CONCLUSIONS

Our results suggest the utility of a portable EEG monitor to measure different sleep stages, transitions, and arousals; however, the accuracy in measuring different sleep stages by the SedLine monitor varies compared with PSG. Our results also support previous findings that sleep is fragmented in critically ill patients. Further research is necessary to develop portable EEG monitors that have higher agreement with PSG.

Environmental Factors Promoting Neural Plasticity: Insights from Animal and Human Studies

We do not all grow older in the same way. Some individuals have a cognitive decline earlier and faster than others who are older in years but cerebrally younger. This is particularly easy to verify in people who have maintained regular physical activity and healthy and cognitively stimulating lifestyle and even in the clinical field. There are patients with advanced neurodegeneration, such as Alzheimer's disease (AD), that, despite this, have mild cognitive impairment. What determines this interindividual difference? Certainly, it cannot be the result of only genetic factors. We are made in a certain manner and what we do acts on our brain. In fact, our genetic basis can be modulated, modified, and changed by our experiences such as education and life events; daily, by sleep schedules and habits; or also by dietary elements. And this can be seen as true even if our experiences are indirectly driven by our genetic basis. In this paper, we will review some current scientific research on how our experiences are able to modulate the structural organization of the brain and how a healthy lifestyle (regular physical activity, correct sleep hygiene, and healthy diet) appears to positively affect cognitive reserve.

Abnormal amplitude of low-frequency fluctuations associated with rapid-eye movement in chronic primary insomnia patients

Purpose

Chronic primary insomnia (CPI) is the most prevalent sleep disorder worldwide. CPI manifests as difficulties in sleep onset, maintaining sleep, prolonged sleep latency, and daytime impairment and is often accompanied by cognitive problems such as poor academic performance, poor attention, and decreased memory. The most popular explanation of insomnia is hyperarousal or increased activities of neurons. Rapid eye movement (REM) sleep detected by polysomnography (PSG) exhibits a positive relationship with brain homeostasis and can be helpful for optimally preparing an organism for emotional and social function. Limited work has been performed to explore brain function of insomnia patients in combination with PSG analysis.

Results

We observed increased ALFF within areas related to hyperarousal such as the midbrain and bilateral extra-nucleus, whereas decreased ALFF was observed within areas associated with memory and attention involving the parietal and occipital lobule and others. Furthermore, the altered ALFF was associated with the duration of insomnia, sleep efficiency, duration of REM, latency of RME and ratio of REM.

Materials and Methods

In this study, we recruited twenty-five CPI patients and twenty-five normal sleep (NS) volunteers as a control group to investigate the amplitude of low-frequency fluctuations (ALFF) and the correlation between those altered ALFF regions through resting-state fMRI and PSG data.

Conclusions

These findings suggest that hyperarousal reflected by ALFF abnormality within brain areas related to cognition and emotion in insomnia associated with REM sleep.

Exercise as a Positive Modulator of Brain Function

Various forms of exercise have been shown to prevent, restore, or ameliorate a variety of brain disorders including dementias, Parkinson's disease, chronic stress, thyroid disorders, and sleep deprivation, some of which are discussed here. In this review, the effects on brain function of various forms of exercise and exercise mimetics in humans and animal experiments are compared and discussed. Possible mechanisms of the beneficial effects of exercise including the role of neurotrophic factors and others are also discussed.

The effect of melatonin on early postoperative cognitive decline in elderly patients undergoing hip arthroplasty: A randomized controlled trial

STUDY OBJECTIVE

The purpose of the present study was to investigate whether exogenous melatonin supplementation could ameliorate early postoperative cognitive decline (POCD) in aged patients undergoing hip arthroplasty with spinal anesthesia.

DESIGN

Prospective cohort study.

SETTING

Department of Anesthesiology, Jinling Hospital, Nanjing University, Nanjing, China.

PATIENTS

One hundred and thirty-nine patients with ASA I-III, older than 65yr of age (mean age: 74.5±5.5; gender: male 53 and female 86), scheduled for hip arthroplasty were included in the present study.

INTERVENTIONS

Patients were randomized to receive 1mg oral melatonin or placebo daily 1h before bedtime one day before surgery and for another 5 consecutive days postoperatively.

MEASUREMENTS

The subject assessment, including Mini-Mental State Examination (MMSE) score, subjective sleep quality, general well-being, postoperative fatigue, and visual analogue scale for pain were evaluated pre-operatively and at days 1, 3, 5, and 7 after surgery.

MAIN RESULTS

The MMSE score in the control group decreased significantly after surgery when compared with its own preoperative value or the melatonin group at days 1, 3, and 5. However, the MMSE score in the melatonin group remained unchanged during the 7days of monitoring. In addition, significant postoperative impairments of subjective sleep quality, general well-being, and fatigue were found in the control group when compared with the melatonin group.

CONCLUSION

Peroperative melatonin supplementation might improve early POCD, suggesting restoration of normal circadian function with good sleep quality may be one of the key factors in preventing or treating POCD.

Effects of Sleep Deprivation on Spatial Learning and Memory in Juvenile and Young Adult Rats

Sleepiness is commonly seen in adolescents and can negatively impact school performance. Little research has investigated the impact of sleepiness in juvenile animals on spatial learning. Sprague-Dawley juvenile (<30 days) and young adult (>60 days) rats were sleep deprived for 24 hours and tested, along with controls, in a water maze task. Sleep deprived juveniles were slower to learn the location of the hidden platform than controls; however, adult performance was not impaired. Sleep deprivation did not impair recall during a probe trial for either age group. Sleep deprivation prior to testing slowed spatial learning in juveniles but not adults.

Neurologic Diseases and Sleep

Sleep disorders and neurologic illness are common and burdensome in their own right; when combined, they can have tremendous negative impact at an individual level as well as societally. The socioeconomic burden of sleep disorders and neurologic illness can be identified, but the real cost of these conditions lies far beyond the financial realm. There is an urgent need for comprehensive care and support systems to help with the burden of disease. Further research in improving patient outcomes in those who suffer with these conditions will help patients and their families, and society in general.

The Association between Sleep Disturbances and Depression among Firefighters: Emotion Dysregulation as an Explanatory Factor

STUDY OBJECTIVES

To investigate emotion regulation difficulties in association with self-reported insomnia symptoms, nightmares, and depression symptoms in a sample of current and retired firefighters.

METHODS

A total of 880 current and retired United States firefighters completed a web-based survey of firefighter behavioral health. Self-report measures included the Center for Epidemiologic Studies Depression Scale, Insomnia Severity Index, PTSD Checklist, and Difficulties in Emotion Regulation Scale.

RESULTS

A notable portion of participants reported clinically significant depression symptoms (39.6%) and insomnia symptoms (52.7%), as well as nightmare problems (19.2%), each of which demonstrated a strong association with emotion regulation difficulties (rs = 0.56-0.80). Bootstrapped mediation analyses revealed that the indirect effects of overall emotion regulation difficulties were significant both for the relationship between insomnia and depression (95% CI: 0.385-0.566) and nightmares and depression (95% CI: 1.445-2.365). Limited access to emotion regulation strategies emerged as the strongest, significant indirect effect for both relationships (insomnia 95% CI: 0.136-0.335; nightmares 95% CI: 0.887-1.931).

CONCLUSIONS

Findings extend previous affective neuroscience research by providing evidence that insomnia and nightmares may influence depression symptoms specifically through the pathway of explicit emotion regulation difficulties. Sleep disturbances may impair the ability to access and leverage emotion regulation strategies effectively, thus conferring risk for negative affect and depression.

Neurocognitive Game between Risk Factors, Sleep and Suicidal Behaviour

INTRODUCTION

Sleep and lifestyles interact to allow the appropriate development of cerebral structures, and prevention of mood disorders. But just a hand of articles identified a precise relationship between these two above, and the probability to develop a suicidal behaviour.

OBJECTIVE

The aim of this study is to explore how the suicidal behaviour is associated in simultaneous with sleep components, psychological stress, depression, anxiety, well-being, addiction, and global health of participants; and if it is also influenced by the sociodemographic profile of each subject.

METHODS

The present study was led by a questionnaire incorporating McNair test, and an incorporated score to evaluate suicide tendencies. The questionnaire also included socio-demographic items and other questions to exhibit a profile of suicide tendency for each individual.

RESULTS

Our results showed that the stress levels and well-being are comparable according to gender. Specifically the results showed that lack of sleep combined with a low score to McNair test strongly affects the suicidal tendency, while score of memory and attention decreased.

CONCLUSIONS

The suicidal behaviour is closely linked with sleep parameters which decreased accordingly, and the family's history of medication and suicidal behaviour.

Sleep restriction can attenuate prioritization benefits on declarative memory consolidation

As chronic sleep restriction is a widespread problem among adolescents, the present study investigated the effects of a 1-week sleep restriction (SR) versus control period on the consolidation of long-term memory for prose passages. We also determined whether the benefit of prioritization on memory is modulated by adequate sleep occurring during consolidation. Fifty-six healthy adolescents (25 male, aged 15-19 years) were instructed to remember a prose passage in which half of the content was highlighted (prioritized), and were told that they would receive an additional bonus for remembering highlighted content. Following an initial free recall test, participants underwent a 7-night period in which they received either a 5-h (SR) or 9-h (control) nightly sleep opportunity, monitored by polysomnography on selected nights. Free recall of the passage was tested at the end of the sleep manipulation period (1 week after encoding), and again 6 weeks after encoding. Recall of highlighted content was superior to that of non-highlighted content at all three time-points (initial, 1 week, 6 weeks). This beneficial effect of prioritization on memory was stronger 1 week relative to a few minutes after encoding for the control, but not the SR group. N3 duration was similar in the control and SR groups. Overall, the present study shows that the benefits of prioritization on memory are enhanced over time, requiring time and sleep to unfold fully. Partial sleep deprivation (i.e. 5-h nocturnal sleep opportunity) may attenuate such benefits, but this may be offset by preservation of N3 sleep duration.

Application of Transcranial Direct Current Stimulation in Neurorehabilitation: The Modulatory Effect of Sleep

The relationship between sleep disorders and neurological disorders is often reciprocal, such that sleep disorders are worsened by neurological symptoms and that neurological disorders are aggravated by poor sleep. Animal and human studies further suggest that sleep disruption not only worsens single neurological symptoms but may also lead to long-term negative outcomes. This suggests that sleep may play a fundamental role in neurorehabilitation and recovery. We further propose that sleep may not only alter the efficacy of behavioral treatments but also plasticity-enhancing adjunctive neurostimulation methods, such as transcranial direct current stimulation (tDCS). At present, sleep receives little attention in the fields of neurorehabilitation and neurostimulation. In this review, we draw together the strands of evidence from both fields of research to highlight the proposition that sleep is an important parameter to consider in the application of tDCS as a primary or adjunct rehabilitation intervention.

Children's Sleep and Academic Achievement: The Moderating Role of Effortful Control

Poor sleep is thought to interfere with children's learning and academic achievement (AA). However, existing research and theory indicate there are factors that may mitigate the academic risk associated with poor sleep. The purpose of this study was to examine the moderating role of children's effortful control (EC) on the relation between sleep and AA in young children. One hundred and three 4.5- to 7-year-olds (M = 5.98 years, SD = 0.61) wore a wrist-based actigraph for five continuous weekday nights. Teachers and coders reported on children's EC. EC was also assessed with a computer-based task at school. Additionally, we obtained a standardized measure of children's AA. There was a positive main effect of sleep efficiency to AA. Several relations between sleep and AA were moderated by EC and examination of the simple slopes indicated that the negative relation between sleep and AA was only significant at low levels of EC.

Dream to Predict? REM Dreaming as Prospective Coding

The dream as prediction seems inherently improbable. The bizarre occurrences in dreams never characterize everyday life. Dreams do not come true! But assuming that bizarreness negates expectations may rest on a misunderstanding of how the predictive brain works. In evolutionary terms, the ability to rapidly predict what sensory input implies-through expectations derived from discerning patterns in associated past experiences-would have enhanced fitness and survival. For example, food and water are essential for survival, associating past experiences (to identify location patterns) predicts where they can be found. Similarly, prediction may enable predator identification from what would have been only a fleeting and ambiguous stimulus-without prior expectations. To confront the many challenges associated with natural settings, visual perception is vital for humans (and most mammals) and often responses must be rapid. Predictive coding during wake may, therefore, be based on unconscious imagery so that visual perception is maintained and appropriate motor actions triggered quickly. Speed may also dictate the form of the imagery. Bizarreness, during REM dreaming, may result from a prospective code fusing phenomena with the same meaning-within a particular context. For example, if the context is possible predation, from the perspective of the prey two different predators can both mean the same (i.e., immediate danger) and require the same response (e.g., flight). Prospective coding may also prune redundancy from memories, to focus the image on the contextually-relevant elements only, thus, rendering the non-relevant phenomena indeterminate-another aspect of bizarreness. In sum, this paper offers an evolutionary take on REM dreaming as a form of prospective coding which identifies a probabilistic pattern in past events. This pattern is portrayed in an unconscious, associative, sensorimotor image which may support cognition in wake through being mobilized as a predictive code. A particular dream illustrates.

Not only … but also: REM sleep creates and NREM Stage 2 instantiates landmark junctions in cortical memory networks

This article argues both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep contribute to overnight episodic memory processes but their roles differ. Episodic memory may have evolved from memory for spatial navigation in animals and humans. Equally, mnemonic navigation in world and mental space may rely on fundamentally equivalent processes. Consequently, the basic spatial network characteristics of pathways which meet at omnidirectional nodes or junctions may be conserved in episodic brain networks. A pathway is formally identified with the unidirectional, sequential phases of an episodic memory. In contrast, the function of omnidirectional junctions is not well understood. In evolutionary terms, both animals and early humans undertook tours to a series of landmark junctions, to take advantage of resources (food, water and shelter), whilst trying to avoid predators. Such tours required memory for emotionally significant landmark resource-place-danger associations and the spatial relationships amongst these landmarks. In consequence, these tours may have driven the evolution of both spatial and episodic memory. The environment is dynamic. Resource-place associations are liable to shift and new resource-rich landmarks may be discovered, these changes may require re-wiring in neural networks. To realise these changes, REM may perform an associative, emotional encoding function between memory networks, engendering an omnidirectional landmark junction which is instantiated in the cortex during NREM Stage 2. In sum, REM may preplay associated elements of past episodes (rather than replay individual episodes), to engender an unconscious representation which can be used by the animal on approach to a landmark junction in wake.

Prevention by Regular Exercise of Acute Sleep Deprivation-Induced Impairment of Late Phase LTP and Related Signaling Molecules in the Dentate Gyrus

The dentate gyrus (DG) and CA1 regions of the hippocampus are intimately related physically and functionally, yet they react differently to insults. The purpose of this study was to determine the protective effects of regular treadmill exercise on late phase long-term potentiation (L-LTP) and its signaling cascade in the DG region of the hippocampus of rapid eye movement (REM) sleep-deprived rats. Adult Wistar rats ran on treadmills for 4 weeks then were acutely sleep deprived for 24 h using the modified multiple platform method. After sleep deprivation, the rats were anesthetized and L-LTP was induced in the DG region. Extracellular field potentials from the DG were recorded in vivo, and levels of L-LTP-related signaling proteins were assessed both before and after L-LTP expression using immunoblot analysis. Sleep deprivation reduced the basal levels of phosphorylated cAMP response element-binding protein (P-CREB) as well as other upstream modulators including calcium/calmodulin kinase IV (CaMKIV) and brain-derived neurotrophic factor (BDNF) in the DG of the hippocampus. Regular exercise prevented impairment of the basal levels of P-CREB and total CREB as well as those of CaMKIV in sleep-deprived animals. Furthermore, regular exercise prevented sleep deprivation-induced inhibition of L-LTP and post-L-LTP downregulation of P-CREB and BDNF levels in the DG. The current findings show that our exercise regimen prevents sleep deprivation-induced deficits in L-LTP as well as the basal and poststimulation levels of key signaling molecules.