Sleep and plasticity in the visual cortex: more than meets the eye

Nest positioning on motor development, sleep patterns, weight gain in preterm infants: systematic review

The aim was to evaluate the effects of Nest Positioning (NP) on motor development, sleep patterns, and weight gain in preterm newborns (PTNB) hospitalized in a neonatal intensive care unit (NICU). This study was constructed based on PRISMA guideline criteria. Systematic research was carried out in electronic databases: MEDLINE via PubMed, Web of Science, Scopus, and VHL-BIREME following the PICOS strategy. Studies with PTNB populations who were hospitalized in the NICU and received therapeutic NP as an intervention strategy in this population were included in this study. We sought outcomes related to sleep patterns, weight gain, and motor development. After selection, 12 studies were included in this systematic review, of which 5 (41.7%) evaluated motor development as their primary outcome, 6 (50%) sleep-wake cycle patterns, and 1 (8.3%), weight gain and, subsequently, hospital discharge. Qualitative results indicate that prolonged exposure to decubitus variations may favor PTNB hospitalized in NICUs acquiring flexor postures, stimulate their midline, and increase their total sleep time. Studies reported no adverse effects regarding the use of NP. Evidence suggests that NP benefits motor development and sleep pattern in PTNB hospitalized in NICUs. IMPACT: Nest positioning improves sleep quality in preterm newborns hospitalized in neonatal intensive care unit. Nest positioning improves motor development in preterm newborns hospitalized in neonatal intensive care unit. No evidence of nest positioning on weight gain was observed. Half of the included clinical studies showed good methodological quality. Nesting positioning is a secure and cost-effective method.

Chronic Vestibular Hypofunction Is Associated with Impaired Sleep: Results from the DizzyReg Patient Registry

Temporary or permanent vestibular hypofunction has been hypothesized to affect circadian rhythm, sleep, and thermoregulation. Chronic or long-term vestibular disorders such as unilateral vestibular hypofunction may have an even greater negative impact on sleep quality than acute vestibular problems. This study examines self-reported sleep quality, as assessed by the Pittsburgh Sleep Quality Index (PSQI), and its association with vestibular symptom duration in a group of patients with vestibular disorders. We used data from the cross-sectional DizzyReg patient registry of the German Center for Vertigo and Balance Disorders outpatient clinic. Vestibular diagnoses were ascertained based on the International Classification of Vestibular Disorders. A total of 137 patients were included (60% female, mean age 55.4 years, standard deviation, SD, 16.7). The mean PSQI total score was 6.3 (SD = 3.2), with 51% reporting overall poor sleep quality. Patients who had vertigo for two years or longer reported significantly poorer global sleep quality (63% vs. 37%, p = 0.021) and significantly more difficulties with sleep latency (79% vs. 56%, p = 0.013) and sleep efficiency (56% vs. 34%, p = 0.022). The association of poor sleep quality with a longer duration of vertigo remained significant after multivariable adjustment. Further research should investigate the interaction of vestibular disorders, sleep, and their potential mechanisms.

β-asarone prolongs sleep via regulating the level of glutamate in the PVN

People of all ages could suffer from sleep disorders, which are increasingly recognized as common manifestations of neurologic disease. Acorus tatarinowii is a herb that has been used in traditional medicine to promote sleep. β-asarone, as the main component of volatile oil obtained from Acorus tatarinowii, may be the main contributor to the sleeping-promoting efficacy of Acorus tatarinowii. In the study, adult male C57BL/6 mice were administered β-asarone at 12.5 mg/kg, 25 mg/kg, and 50 mg/kg. Behavioral experiments showed that β-asarone at 25 mg/kg could significantly improve sleep duration. It was also observed that the proportion of NREM (Non-Rapid Eye Movement) sleep increased considerably after administration of β-asarone. In the PVN (paraventricular nucleus of hypothalamus) region of the hypothalamus, it was observed that the glutamate content decreased after β-asarone treatment. At the same time, the expression of VGLUT2 (vesicular glutamate transporters 2) decreased while the expression of GAD65 (glutamic acid decarboxylase 65) and GABARAP (GABA Type A Receptor-Associated Protein) increased in the hypothalamus, suggesting that β-asarone may suppress arousal by reducing glutamate and promoting transformation of glutamate to the inhibitory neurotransmitter GABA (γ-aminobutyric acid). This study is the first to focus on the association between β-asarone and sleep, shedding perspectives for pharmacological applications of β-asarone and providing a new direction for future research.

Adolescent sleep and the foundations of prefrontal cortical development and dysfunction

Modern life poses many threats to good-quality sleep, challenging brain health across the lifespan. Curtailed or fragmented sleep may be particularly damaging during adolescence, when sleep disruption by delayed chronotypes and societal pressures coincides with our brains preparing for adult life via intense refinement of neural connectivity. These vulnerabilities converge on the prefrontal cortex, one of the last brain regions to mature and a central hub of the limbic-cortical circuits underpinning decision-making, reward processing, social interactions and emotion. Even subtle disruption of prefrontal cortical development during adolescence may therefore have enduring impact. In this review, we integrate synaptic and circuit mechanisms, glial biology, sleep neurophysiology and epidemiology, to frame a hypothesis highlighting the implications of adolescent sleep disruption for the neural circuitry of the prefrontal cortex. Convergent evidence underscores the importance of acknowledging, quantifying and optimizing adolescent sleep's contributions to normative brain development and to lifelong mental health.

Is paradoxical sleep setting up innate and acquired complex sensorimotor and adaptive behaviours?: A proposed function based on literature review

We summarize here the progress in identifying the neuronal network as well as the function of paradoxical sleep and the gaps of knowledge that should be filled in priority. The core system generating paradoxical sleep localized in the brainstem is now well identified, and the next step is to clarify the role of the forebrain in particular that of the hypothalamus including the melanin-concentrating hormone neurons and of the basolateral amygdala. We discuss these two options, and also the discovery that cortical activation during paradoxical sleep is restricted to a few limbic cortices activated by the lateral supramammillary nucleus and the claustrum. Such activation nicely supports the findings recently obtained showing that neuronal reactivation occurs during paradoxical sleep in these structures, and induces both memory consolidation of important memory and forgetting of less relevant ones. The question that still remains to be answered is whether paradoxical sleep is playing more crucial roles in processing emotional and procedural than other types of memories. One attractive hypothesis is that paradoxical sleep is responsible for erasing negative emotional memories, and that this function is not properly functioning in depressed patients. On the other hand, the presence of a muscle atonia during paradoxical sleep is in favour of a role in procedural memory as new types of motor behaviours can be tried without harm during the state. In a way, it also fits with the proposed role of paradoxical sleep in setting up the sensorimotor system during development.

Disrupted Brain Functional Network Topology in Essential Tremor Patients With Poor Sleep Quality

Sleep disturbances, especially poor quality of sleep (QoS), are common among essential tremor (ET) patients and may have adverse effects on their quality of life, but the etiology driving the poor QoS in these individuals remains inadequately understood. Few data are available on the neuroimaging alterations of ET with poor QoS. Thirty-eight ET patients with poor QoS (SleET), 48 ET patients with normal QoS (NorET), and 80 healthy controls (HCs) participated in this study. All subjects underwent a 3.0-T magnetic resonance imaging (MRI) scan for resting-state functional MRI data collection. Then, the whole-brain functional connectome was constructed by thresholding the partial correlation matrices of 116 brain regions. Graph theory and network-based statistical analyses were performed. We used a non-parametric permutation test for group comparisons of topological metrics. Partial correlation analyses between the topographical features and clinical characteristics were conducted. The SleET and NorET groups exhibited decreased clustering coefficients, global efficiency, and local efficiency and increased the characteristic path length. Both of these groups also showed reduced nodal degree and nodal efficiency in the left superior dorsolateral frontal gyrus, superior frontal medial gyrus (SFGmed), posterior cingulate gyrus (PCG), lingual gyrus, superior occipital gyrus, right middle occipital gyrus, and right fusiform gyrus. The SleET group additionally presented reduced nodal degrees and nodal efficiency in the right SFGmed relative to the NorET and HC groups, and nodal efficiency in the right SFGmed was negatively correlated with the Pittsburgh Sleep Quality Index score. The observed impaired topographical organizations of functional brain networks within the central executive network (CEN), default mode network (DMN), and visual network serve to further our knowledge of the complex interactions between tremor and sleep, adding to our understanding of the underlying neural mechanisms of ET with poor QoS.

Subcortical and Cerebellar Neural Correlates of Prodromal Alzheimer’s Disease with Prolonged Sleep Latency

Background: Despite the important associations among sleep, Alzheimer’s disease (AD), subcortical structures, and the cerebellum, structural and functional magnetic resonance imaging (MRI) with regard to these regions and sleep on patients in AD trajectory are scarce. Objective: This study aimed to evaluate the influence of prolonged sleep latency on the structural and functional alterations in the subcortical and cerebellar neural correlates in amyloid-β positive amnestic mild cognitive impairment patients (Aβ+aMCI). Methods: A total of 60 patients with aMCI who were identified as amyloid positive ([18F] flutemetamol+) were recruited in the study, 24 patients with normal sleep latency (aMCI-n) and 36 patients prolonged sleep latency (aMCI-p). Cortical thickness and volumes between the two groups were compared. Volumetric analyses were implemented on the brainstem, thalamus, and hippocampus. Subcortical and cerebellar resting state functional connectivity (FC) differences were measured between the both groups through seed-to-voxel analysis. Additionally, group x Aβ interactive effects on FC values were tested with a general linear model. Result: There was a significantly decreased brainstem volume in aMCI-p subjects. We observed a significant reduction of the locus coeruleus (LC) FC with frontal, temporal, insular cortices, hippocampus, and left thalamic FC with occipital cortex. Moreover, the LC FC with occipital cortex and left hippocampal FC with frontal cortex were increased in aMCI-p subjects. In addition, there was a statistically significant group by regional standardized uptake value ratio interactions discovered in cerebro-cerebellar networks. Conclusion: The aforementioned findings suggest that prolonged sleep latency may be a detrimental factor in compromising structural and functional correlates of subcortical structures and the cerebellum, which may accelerate AD pathophysiology.

Longitudinal Analysis of Sleep-Wake States in Neonatal Rats Subjected to Hypoxia-Ischemia

OBJECTIVE

Sleep is necessary for brain maturation in infants. Perinatal hypoxic-ischemic encephalopathy (HIE) is a major cause of chronic neurological disease in infants. Although the developmental changes of electroencephalogram (EEG) in human newborns have been described, little is known about the EEG normal maturation characteristics in rodents and the changes in sleep-awake states caused by hypoxia-ischemia (HI). This study aimed to investigate the pathological response of sleep-wake states in neonatal rats with HIE.

METHODS

We constructed HIE and sham models on postnatal day (P) 3 rats and continuously monitored them using electroencephalography and electromyography for up to P12. The distribution of sleep-wake states was analyzed to estimate the effects of HIE.

RESULTS

Compared with the sham group, the HI group showed lower rapid eye movement (REM) sleep percentage, but wake percentage and frequency was higher during P4-P12. The frequency of REM and non-rapid eye movement (NREM) sleep increased and the duration of REM and NREM sleep decreased after HI induction. However, it gradually returned to the normal level with an increase in daytime.

CONCLUSION

HI damage alters the sleep-wake patterns during early neural development. The findings provide a comprehensive assessment of serial sleep-wake state recordings in neonatal rats from P4-P12.

Effects of transcutaneous auricular vagus nerve stimulation on brain functional connectivity of medial prefrontal cortex in patients with primary insomnia

As a representative of acupuncture and nonpharmaceutical therapy, auricular acupuncture has been widely for the treatment of insomnia. Transcutaneous auricular vagus nerve stimulation (taVNS) is a combination of auricular point stimulation and vagus nerve stimulation. It can not only treat primary insomnia effectively, but also is noninvasive, painless, portable and economical. The medial prefrontal cortex (mPFC) is a core region of default mode network (DMN), which is important for maintenance of sleep. However, the mechanism of taVNS in alleviating primary insomnia (PI) remains to be clarified. In this study, we found that taVNS could not only effectively reduce the score of Pittsburgh Sleep Quality Index, but also decreased functional connection (FC) between the left mPFC and bilateral dorsal anterior cingulate gyrus as well as FC between the right mPFC and the occipital cortex in patients with PI. Furthermore, the decrease in FC was positively correlated with the decline of sleep index score. Therefore, we proposed that treatment with taVNS can improve sleep quality and prolong sleep duration in patients with PI by reducing FC within DMN, FC between DMN and salience network, as well as FC between DMN and the occipital cortex. This may be one of mechanisms of taVNS in treating PI.

Occipital sleep spindles predict sequence learning in a visuo-motor task

STUDY OBJECTIVES

The brain appears to use internal models to successfully interact with its environment via active predictions of future events. Both internal models and the predictions derived from them are based on previous experience. However, it remains unclear how previously encoded information is maintained to support this function, especially in the visual domain. In the present study, we hypothesized that sleep consolidates newly encoded spatio-temporal regularities to improve predictions afterwards.

METHODS

We tested this hypothesis using a novel sequence-learning paradigm that aimed to dissociate perceptual from motor learning. We recorded behavioral performance and high-density electroencephalography (EEG) in male human participants during initial training and during testing two days later, following an experimental night of sleep (n = 16, including high-density EEG recordings) or wakefulness (n = 17).

RESULTS

Our results show sleep-dependent behavioral improvements correlated with sleep-spindle activity specifically over occipital cortices. Moreover, event-related potential (ERP) responses indicate a shift of attention away from predictable to unpredictable sequences after sleep, consistent with enhanced automaticity in the processing of predictable sequences.

CONCLUSIONS

These findings suggest a sleep-dependent improvement in the prediction of visual sequences, likely related to visual cortex reactivation during sleep spindles. Considering that controls in our experiments did not fully exclude oculomotor contributions, future studies will need to address the extent to which these effects depend on purely perceptual versus oculomotor sequence learning.

Prognostic value of neonatal EEG following therapeutic hypothermia in survivors of hypoxic-ischemic encephalopathy

OBJECTIVE

Early prediction of neurological deficits following neonatal hypoxic-ischemic encephalopathy (HIE) may help to target support. Neonatal animal models suggest that recovery following hypoxia-ischemia depends upon cortical bursting. To test whether this holds in human neonates, we correlated the magnitude of cortical bursting during recovery (≥postnatal day 3) with neurodevelopmental outcomes.

METHODS

We identified 41 surviving infants who received therapeutic hypothermia for HIE (classification at hospital discharge: 19 mild, 18 moderate, 4 severe) and had 9-channel electroencephalography (EEG) recordings as part of their routine care. We correlated burst power with Bayley-III cognitive, motor and language scores at median 24 months. To examine whether EEG offered additional prognostic information, we controlled for structural MRI findings.

RESULTS

Higher power of central and occipital cortical bursts predicted worse cognitive and language outcomes, and higher power of central cortical bursts predicted worse motor outcome, all independently of structural MRI findings.

CONCLUSIONS

Clinical EEG after postnatal day 3 may provide additional prognostic information by indexing persistent active mechanisms that either support recovery or exacerbate brain damage, especially in infants with less severe encephalopathy.

SIGNIFICANCE

These findings could allow for the effect of clinical interventions in the neonatal period to be studied instantaneously in the future.

Circadian Rhythm Disorders and Corresponding Functional Brain Abnormalities in Young Female Nurses: A Preliminary Study

Objective: Shift work is associated with a decrease in melatonin level and perturbation of the circadian rhythm; however, it is unknown if these lead to functional brain changes. In this study, we investigated whether circadian rhythm disorders caused by shift work are related to changes in brain functional connectivity (FC) and regional homogeneity (ReHo) using whole-brain resting-state functional magnetic resonance imaging (fMRI).

Methods: This prospective case-control study included nine female night shift nurses and nine age-matched female day work nurses with normal sleep rhythms. To assess sleep quality and mood, participants were asked to complete questionnaires. Serum melatonin and cortisol levels were measured. ReHo of whole-brain resting-state function and seed-based FC of the bilateral hypothalamus were compared between groups. Variables that differed significantly between groups were used to examine the association between questionnaire scores and hormone levels and fMRI data.

Results: The night shift nurses had significantly lower sleep quality and melatonin levels; lower ReHo activation in the bilateral cerebellar hemisphere and higher ReHo in the bilateral occipital lobe and left parietal lobe; and higher FC from the hypothalamus to the right cingulate gyrus, right putamen, and vermis than did the day shift nurses. Activation of the right cerebellar hemisphere left superior parietal gyrus, and the right superior occipital gyrus was correlated with sleep quality scores. Moreover, activation of the right cerebellar hemisphere (r = 0.583, P = 0.011) was correlated with melatonin levels, and higher sleepiness scores were associated with stronger FC between the hypothalamus and vermis (r = 0.501, P = 0.034).

Conclusions: Circadian rhythm disorder caused by night shift work can lead to a decrease in sleep quality and melatonin level, as well as a series of changes in brain FC and ReHo.

Sleep-wake regulation in preterm and term infants

Study Objectives

In adults, wakefulness can be markedly prolonged at the expense of sleep, e.g. to stay vigilant in the presence of a stressor. These extra-long wake bouts result in a heavy-tailed distribution (highly right-skewed) of wake but not sleep durations. In infants, the relative importance of wakefulness and sleep are reversed, as sleep is necessary for brain maturation. Here, we tested whether these developmental pressures are associated with the unique regulation of sleep–wake states.

Methods

In 175 infants of 28–40 weeks postmenstrual age (PMA), we monitored sleep–wake states using electroencephalography and behavior. We constructed survival models of sleep–wake bout durations and the effect of PMA and other factors, including stress (salivary cortisol), and examined whether sleep is resilient to nociceptive perturbations (a clinically necessary heel lance).

Results

Wake durations followed a heavy-tailed distribution as in adults and lengthened with PMA and stress. However, differently from adults, active sleep durations also had a heavy-tailed distribution, and with PMA, these shortened and became vulnerable to nociception-associated awakenings.

Conclusions

Sleep bouts are differently regulated in infants, with especially long active sleep durations that could consolidate this state’s maturational functions. Curtailment of sleep by stress and nociception may be disadvantageous, especially for preterm infants given the limited value of wakefulness at this age. This could be addressed by environmental interventions in the future.

The Ontogenesis of Mammalian Sleep: Form and Function

PURPOSE OF REVIEW

To present an up-to-date review and synthesis of findings about perinatal sleep development and function. I discuss landmark events in sleep ontogenesis, evidence that sleep promotes brain development and plasticity, and experimental considerations in this topic.

RECENT FINDINGS

Mammalian sleep undergoes dramatic changes in expression and regulation during perinatal development. This includes a progressive decrease in rapid-eye-movement (REM) sleep time, corresponding increases in nonREM sleep and wake time, and the appearance of mature sleep regulatory processes (homeostatic and circadian). These developmental events coincide with periods of rapid brain maturation and heightened synaptic plasticity. The latter involve an initial experience-independent phase, when circuit development is guided by spontaneous activity, and later occurring critical periods, when these circuits are shaped by experience.

SUMMARY

These ontogenetic changes suggest important interactions between sleep and brain development. More specifically, sleep may promote developmental programs of synaptogenesis and synaptic pruning and influence the opening and closing of critical periods of brain plasticity.

Sleep, brain development, and autism spectrum disorders: Insights from animal models

Sleep is an evolutionarily conserved and powerful drive, although its complete functions are still unknown. One possible function of sleep is that it promotes brain development. The amount of sleep is greatest during ages when the brain is rapidly developing, and sleep has been shown to influence critical period plasticity. This supports a role for sleep in brain development and suggests that abnormal sleep in early life may lead to abnormal development. Autism spectrum disorder (ASD) is the most prevalent neurodevelopmental disorder in the United States. It is estimated that insomnia affects 44%-86% of the ASD population, predicting the severity of ASD core symptoms and associated behavioral problems. Sleep problems impact the quality of life of both ASD individuals and their caregivers, thus it is important to understand why they are so prevalent. In this review, we explore the role of sleep in early life as a causal factor in ASD. First, we review fundamental steps in mammalian sleep ontogeny and regulation and how sleep influences brain development. Next, we summarize current knowledge gained from studying sleep in animal models of ASD. Ultimately, our goal is to highlight the importance of understanding the role of sleep in brain development and the use of animal models to provide mechanistic insight into the origin of sleep problems in ASD.

The relationship between sleep efficiency and clinical symptoms is mediated by brain function in major depressive disorder

BACKGROUND

Sleep disturbance is a common and key symptom that affects most of patients with major depressive disorder (MDD). However, neural substrates underlying sleep disturbance and their clinical relevance in depression remain unclear.

METHODS

Ninety-six MDD patients underwent resting-state functional MRI. Fractional amplitude of low-frequency fluctuation (fALFF) and resting-state functional connectivity (rsFC) were used to measure brain function. Overnight polysomnography was performed to objectively measure sleep efficiency (SE), which was used to classify patients into normal sleep efficiency (NSE) and low sleep efficiency (LSE) groups. Between-group differences in fALFF and rsFC were examined using two-sample t-tests. Moreover, correlation and mediation analyses were conducted to test for potential associations between SE, brain functional changes, and clinical variables.

RESULTS

LSE group showed decreased fALFF in right cuneus, thalamus, and middle temporal gyrus compared to NSE group. MDD patients with low SE also exhibited lower rsFC of right cuneus to right lateral temporal cortex, which was associated with more severe depression and anxiety symptoms. More importantly, mediation analyses revealed that the relationships between SE and severity of depression and anxiety symptoms were significantly mediated by the altered rsFC. In addition, these low SE-related brain functional alterations were not affected by antidepressant medication and were independent of structural changes.

LIMITATIONS

The lack of healthy controls because of "first-night effect".

CONCLUSION

These findings not only may expand existing knowledge about neuropathology of sleep disturbance in depression, but also may inform real-world clinical practice by improving depression and anxiety symptoms through sleep regulation.

The Relationship between Sleep Bruxism Intensity and Renalase Concentration-An Enzyme Involved in Hypertension Development

Background and objectives: Renalase, a novel amine oxidase, is involved in the development of hypertension. Sleep bruxism (SB) is a sleep-related behavior characterized by rhythmic or non-rhythmic activity of the masticatory muscles, which leads to the mechanical wear of teeth, pain in the masticatory muscles, and disturbed sleep. Recent studies indicate that SB plays a role in increased blood pressure. Therefore, this study aimed to determine the relationship between sleep bruxism intensity and renalase concentration, which may help in the future to elucidate the pathogenesis of hypertension and other cardiovascular disorders. Material and methods: SB was evaluated in 87 adult patients using single-night diagnostic polysomnography with video and audio recordings, and the episodes of bruxism were scored according to the standards of the American Academy of Sleep Medicine. The levels of serum renalase were measured in the patients using enzyme-linked immunosorbent assay kits. Results: SB (Bruxism Episode Index (BEI) ≥2) was diagnosed in 54% (n = 47) of the studied population, and the mean concentration of renalase was found to be decreased in the hypertensive group compared with the normotensive group (133.33 ± 160.71 vs 219.23 ± 220.58, p = 0.047). In addition, a linear negative correlation was observed between the renalase concentration and the body mass index (BMI) in the SB group (r = 0.38, p < 0.05) but not in controls. Thus, higher BEI and higher BMI were identified as factors independently associated with the lower concentration of renalase, but only in the group of patients which had a blood renalase concentration of >212.5 ng/mL. Conclusion: There exists an association between renalase concentration and SB intensity, and further studies are needed to clarify the role of renalase in the pathogenesis of hypertension and other cardiovascular disorders.

Mechanisms of systems memory consolidation during sleep

Long-term memory formation is a major function of sleep. Based on evidence from neurophysiological and behavioral studies mainly in humans and rodents, we consider the formation of long-term memory during sleep as an active systems consolidation process that is embedded in a process of global synaptic downscaling. Repeated neuronal replay of representations originating from the hippocampus during slow-wave sleep leads to a gradual transformation and integration of representations in neocortical networks. We highlight three features of this process: (i) hippocampal replay that, by capturing episodic memory aspects, drives consolidation of both hippocampus-dependent and non-hippocampus-dependent memory; (ii) brain oscillations hallmarking slow-wave and rapid-eye movement sleep that provide mechanisms for regulating both information flow across distant brain networks and local synaptic plasticity; and (iii) qualitative transformations of memories during systems consolidation resulting in abstracted, gist-like representations.

How Sleep Shapes Thalamocortical Circuit Function in the Visual System

Recent data have shown that sleep plays a beneficial role for cognitive functions such as declarative memory consolidation and perceptual learning. In this article, we review recent findings on the role of sleep in promoting adaptive visual response changes in the lateral geniculate nucleus and primary visual cortex following novel visual experiences. We discuss these findings in the context of what is currently known about how sleep affects the activity and function of thalamocortical circuits and current hypotheses regarding how sleep facilitates synaptic plasticity.

Memory corticalization triggered by REM sleep: mechanisms of cellular and systems consolidation

Once viewed as a passive physiological state, sleep is a heterogeneous and complex sequence of brain states with essential effects on synaptic plasticity and neuronal functioning. Rapid-eye-movement (REM) sleep has been shown to promote calcium-dependent plasticity in principal neurons of the cerebral cortex, both during memory consolidation in adults and during post-natal development. This article reviews the plasticity mechanisms triggered by REM sleep, with a focus on the emerging role of kinases and immediate-early genes for the progressive corticalization of hippocampus-dependent memories. The body of evidence suggests that memory corticalization triggered by REM sleep is a systemic phenomenon with cellular and molecular causes.

Anatomical correlates of rapid eye movement sleep-dependent plasticity in the developing cortex

Rapid eye movement (REM) sleep is expressed at its highest levels during early life when the brain is rapidly developing. This suggests that REM sleep may play important roles in brain maturation and developmental plasticity. We investigated this possibility by examining the role of REM sleep in the regulation of plasticity-related proteins known to govern synaptic plasticity in vitro and in vivo. We combined immunohistochemistry with a classic model of experience-dependent plasticity in the developing brain known to be consolidated during sleep. We found that after the developing visual cortex is triggered to remodel, it is reactivated during REM sleep (as measured by FOS+ and ARC+ cells). This is accompanied by expression of several proteins implicated in synaptic long-term potentiation (PSD95 and phosphorylated (p), mTOR, cofilin, and CREB) across the different cortical layers. These changes did not occur in animals deprived of REM sleep, but were preserved in control animals that were instead awakened in non- (N) REM sleep. Collectively, these findings support a role for REM sleep in developmental brain plasticity.

Tumor necrosis factor alpha in sleep regulation

This review details tumor necrosis factor alpha (TNF) biology and its role in sleep, and describes how TNF medications influence sleep/wake activity. Substantial evidence from healthy young animals indicates acute enhancement or inhibition of endogenous brain TNF respectively promotes and inhibits sleep. In contrast, the role of TNF in sleep in most human studies involves pathological conditions associated with chronic elevations of systemic TNF and disrupted sleep. Normalization of TNF levels in such patients improves sleep. A few studies involving normal healthy humans and their TNF levels and sleep are consistent with the animal studies but are necessarily more limited in scope. TNF can act on established sleep regulatory circuits to promote sleep and on the cortex within small networks, such as cortical columns, to induce sleep-like states. TNF affects multiple synaptic functions, e.g., its role in synaptic scaling is firmly established. The TNF-plasticity actions, like its role in sleep, can be local network events suggesting that sleep and plasticity share biochemical regulatory mechanisms and thus may be inseparable from each other. We conclude that TNF is involved in sleep regulation acting within an extensive tightly orchestrated biochemical network to niche-adapt sleep in health and disease.

Neuroscience: A Distributed Neural Network Controls REM Sleep

How does the brain control dreams? New science shows that a small node of cells in the medulla - the most primitive part of the brain - may function to control REM sleep, the brain state that underlies dreaming.