Sleep Spindles: Mechanisms and Functions

Sleep spindles are burstlike signals in the electroencephalogram (EEG) of the sleeping mammalian brain and electrical surface correlates of neuronal oscillations in thalamus. As one of the most inheritable sleep EEG signatures, sleep spindles probably reflect the strength and malleability of thalamocortical circuits that underlie individual cognitive profiles. We review the characteristics, organization, regulation, and origins of sleep spindles and their implication in non-rapid-eye-movement sleep (NREMS) and its functions, focusing on human and rodent. Spatially, sleep spindle-related neuronal activity appears on scales ranging from small thalamic circuits to functional cortical areas, and generates a cortical state favoring intracortical plasticity while limiting cortical output. Temporally, sleep spindles are discrete events, part of a continuous power band, and elements grouped on an infraslow time scale over which NREMS alternates between continuity and fragility. We synthesize diverse and seemingly unlinked functions of sleep spindles for sleep architecture, sensory processing, synaptic plasticity, memory formation, and cognitive abilities into a unifying sleep spindle concept, according to which sleep spindles 1) generate neural conditions of large-scale functional connectivity and plasticity that outlast their appearance as discrete EEG events, 2) appear preferentially in thalamic circuits engaged in learning and attention-based experience during wakefulness, and 3) enable a selective reactivation and routing of wake-instated neuronal traces between brain areas such as hippocampus and cortex. Their fine spatiotemporal organization reflects NREMS as a physiological state coordinated over brain and body and may indicate, if not anticipate and ultimately differentiate, pathologies in sleep and neurodevelopmental, -degenerative, and -psychiatric conditions.

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Developmental Changes in Sleep Spindle Characteristics and Sigma Power across Early Childhood

Neural Plasticity ◽

10.1155/2016/3670951 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 17

Author(s):

Ian J. McClain ◽

Caroline Lustenberger ◽

Peter Achermann ◽

Jonathan M. Lassonde ◽

Salome Kurth ◽

...

Keyword(s):

Early Childhood ◽

Cognitive Abilities ◽

Brain Connectivity ◽

Nrem Sleep ◽

Developmental Changes ◽

Brain Maturation ◽

Sleep Spindles ◽

Sleep Spindle ◽

Electroencephalogram Eeg ◽

Early Developmental

Sleep spindles, a prominent feature of the non-rapid eye movement (NREM) sleep electroencephalogram (EEG), are linked to cognitive abilities. Early childhood is a time of rapid cognitive and neurophysiological maturation; however, little is known about developmental changes in sleep spindles. In this study, we longitudinally examined trajectories of multiple sleep spindle characteristics (i.e., spindle duration, frequency, integrated spindle amplitude, and density) and power in the sigma frequency range (10–16 Hz) across ages 2, 3, and 5 years (n=8; 3 males). At each time point, nocturnal sleep EEG was recorded in-home after 13-h of prior wakefulness. Spindle duration, integrated spindle amplitude, and sigma power increased with age across all EEG derivations (C3A2, C4A1, O2A1, and O1A2; allps < 0.05). We also found a developmental decrease in mean spindle frequency (p<0.05) but no change in spindle density with increasing age. Thus, sleep spindles increased in duration and amplitude but decreased in frequency across early childhood. Our data characterize early developmental changes in sleep spindles, which may advance understanding of thalamocortical brain connectivity and associated lifelong disease processes. These findings also provide unique insights into spindle ontogenesis in early childhood and may help identify electrophysiological features related to healthy and aberrant brain maturation.

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Rotating waves during human sleep spindles organize global patterns of activity that repeat precisely through the night

eLife ◽

10.7554/elife.17267 ◽

2016 ◽

Vol 5 ◽

Cited By ~ 57

Author(s):

Lyle Muller ◽

Giovanni Piantoni ◽

Dominik Koller ◽

Sydney S Cash ◽

Eric Halgren ◽

...

Keyword(s):

Large Scale ◽

Activity Patterns ◽

Neural Mechanism ◽

Sleep Spindles ◽

Sleep Spindle ◽

Spike Time ◽

Temporal Precision ◽

Global Patterns ◽

Spike Time Dependent Plasticity ◽

Large Scale Networks

During sleep, the thalamus generates a characteristic pattern of transient, 11-15 Hz sleep spindle oscillations, which synchronize the cortex through large-scale thalamocortical loops. Spindles have been increasingly demonstrated to be critical for sleep-dependent consolidation of memory, but the specific neural mechanism for this process remains unclear. We show here that cortical spindles are spatiotemporally organized into circular wave-like patterns, organizing neuronal activity over tens of milliseconds, within the timescale for storing memories in large-scale networks across the cortex via spike-time dependent plasticity. These circular patterns repeat over hours of sleep with millisecond temporal precision, allowing reinforcement of the activity patterns through hundreds of reverberations. These results provide a novel mechanistic account for how global sleep oscillations and synaptic plasticity could strengthen networks distributed across the cortex to store coherent and integrated memories.

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Retrotransposons as Drivers of Mammalian Brain Evolution

Life ◽

10.3390/life11050376 ◽

2021 ◽

Vol 11 (5) ◽

pp. 376

Author(s):

Roberto Ferrari ◽

Nicole Grandi ◽

Enzo Tramontano ◽

Giorgio Dieci

Keyword(s):

Cognitive Abilities ◽

Large Scale ◽

Transcriptional Control ◽

Large Body ◽

Three Dimensional ◽

Brain Evolution ◽

Cell Types ◽

Brain Morphology ◽

Mammalian Brain ◽

And Function

Retrotransposons, a large and diverse class of transposable elements that are still active in humans, represent a remarkable force of genomic innovation underlying mammalian evolution. Among the features distinguishing mammals from all other vertebrates, the presence of a neocortex with a peculiar neuronal organization, composition and connectivity is perhaps the one that, by affecting the cognitive abilities of mammals, contributed mostly to their evolutionary success. Among mammals, hominids and especially humans display an extraordinarily expanded cortical volume, an enrichment of the repertoire of neural cell types and more elaborate patterns of neuronal connectivity. Retrotransposon-derived sequences have recently been implicated in multiple layers of gene regulation in the brain, from transcriptional and post-transcriptional control to both local and large-scale three-dimensional chromatin organization. Accordingly, an increasing variety of neurodevelopmental and neurodegenerative conditions are being recognized to be associated with retrotransposon dysregulation. We review here a large body of recent studies lending support to the idea that retrotransposon-dependent evolutionary novelties were crucial for the emergence of mammalian, primate and human peculiarities of brain morphology and function.

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Spindles are highly heritable as identified by different spindle detectors

SLEEP ◽

10.1093/sleep/zsaa230 ◽

2020 ◽

Author(s):

Jennifer R Goldschmied ◽

Karine Lacourse ◽

Greg Maislin ◽

Jacques Delfrate ◽

Philip Gehrman ◽

...

Keyword(s):

Detection Method ◽

Sleep Spindles ◽

Sleep Spindle ◽

Frequency Range ◽

Same Sex ◽

Detection Algorithms ◽

Detector Method ◽

Scalp Location ◽

Electroencephalogram Eeg ◽

Robust Evidence

Abstract Study Objectives Sleep spindles, a defining feature of stage N2 sleep, are maximal at central electrodes and are found in the frequency range of the electroencephalogram (EEG) (sigma 11–16 Hz) that is known to be heritable. However, relatively little is known about the heritability of spindles. Two recent studies investigating the heritability of spindles reported moderate heritability, but with conflicting results depending on scalp location and spindle type. The present study aimed to definitively assess the heritability of sleep spindle characteristics. Methods We utilized the polysomnography data of 58 monozygotic and 40 dizygotic same-sex twin pairs to identify heritable characteristics of spindles at C3/C4 in stage N2 sleep including density, duration, peak-to-peak amplitude, and oscillation frequency. We implemented and tested a variety of spindle detection algorithms and used two complementary methods of estimating trait heritability. Results We found robust evidence to support strong heritability of spindles regardless of detector method (h2 > 0.8). However not all spindle characteristics were equally heritable, and each spindle detection method produced a different pattern of results. Conclusions The sleep spindle in stage N2 sleep is highly heritable, but the heritability differs for individual spindle characteristics and depends on the spindle detector used for analysis.

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Sleep spindles and cognition in depression

10.31219/osf.io/waz3d ◽

2017 ◽

Author(s):

Leonore Bovy ◽

Martin Dresler ◽

Frederik D Weber

Keyword(s):

Memory Consolidation ◽

Cognitive Abilities ◽

Declarative Memory ◽

Critical Role ◽

Antidepressant Medication ◽

Sleep Spindles ◽

Sleep Spindle ◽

Preliminary Model ◽

Patient Groups ◽

Medication Selection

Sleep plays a critical role in orchestrating several cognitive functions. Sleep spindles are particularly at the forefront of studies on the consolidation of cognitive abilities, such as procedural and declarative memory. Despite that major depressive disorder (MDD) has been linked to sleep spindle alterations, their role in MDD pathogenesis and symptomatology (including memory deficits) is still scarcely investigated. Here, we first provide an overview of sleep and sleep spindle alterations in MDD and their potential effects on memory and cognition. Secondly, limited data suggest that sleep spindles deficits in severe MDD might not only lead to cognitive impairments but primarily affect memory consolidation processes during sleep. Furthermore, it seems likely that many sleep spindle related effects are masked by interacting (antidepressant) medication, selection of mixed patient groups with mild symptomatology as well as use of incomprehensive methodology in analyzing sleep. We propose a preliminary model predicting that impairments in sleep spindle related activity during sleep are mainly responsible for memory consolidation deficits in depressed patients, but that medication augmenting sleep spindle activity can enhance and restore sleep-mediated consolidation. Future studies thus need to scrutinize previous findings on sleep spindle effects in MDD.

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Clinical Decision-Making for Stroke and Aphasia in the Older Adult

Perspectives on Gerontology ◽

10.1044/gero14.1.4 ◽

2009 ◽

Vol 14 (1) ◽

pp. 4-11 ◽

Cited By ~ 1

Author(s):

Jacqueline Hinckley

Keyword(s):

Executive Function ◽

Cerebrovascular Disease ◽

Cognitive Abilities ◽

Clinical Decision Making ◽

Clinical Decision ◽

Cognitive Profile ◽

Focal Lesion ◽

Cognitive Profiles ◽

Supportive Communication ◽

Spaced Retrieval

Abstract A patient with aphasia that is uncomplicated by other cognitive abilities will usually show a primary impairment of language. The frequency of additional cognitive impairments associated with cerebrovascular disease, multiple (silent or diagnosed) infarcts, or dementia increases with age and can complicate a single focal lesion that produces aphasia. The typical cognitive profiles of vascular dementia or dementia due to cerebrovascular disease may differ from the cognitive profile of patients with Alzheimer's dementia. In order to complete effective treatment selection, clinicians must know the cognitive profile of the patient and choose treatments accordingly. When attention, memory, and executive function are relatively preserved, strategy-based and conversation-based interventions provide the best choices to target personally relevant communication abilities. Examples of treatments in this category include PACE and Response Elaboration Training. When patients with aphasia have co-occurring episodic memory or executive function impairments, treatments that rely less on these abilities should be selected. Examples of treatments that fit these selection criteria include spaced retrieval and errorless learning. Finally, training caregivers in the use of supportive communication strategies is helpful to patients with aphasia, with or without additional cognitive complications.

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Pharmacologically Increasing Sleep Spindles Enhances Recognition for Negative and High-arousal Memories

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_00433 ◽

2013 ◽

Vol 25 (10) ◽

pp. 1597-1610 ◽

Cited By ~ 65

Author(s):

Erik J. Kaestner ◽

John T. Wixted ◽

Sara C. Mednick

Keyword(s):

Rem Sleep ◽

Memory Consolidation ◽

Declarative Memory ◽

Memory Performance ◽

Emotional Memory ◽

Limited Range ◽

Sleep Spindles ◽

Sleep Spindle ◽

Emotional Stimuli ◽

Valence And Arousal

Sleep affects declarative memory for emotional stimuli differently than it affects declarative memory for nonemotional stimuli. However, the interaction between specific sleep characteristics and emotional memory is not well understood. Recent studies on how sleep affects emotional memory have focused on rapid eye movement sleep (REM) but have not addressed non-REM sleep, particularly sleep spindles. This is despite the fact that sleep spindles are implicated in declarative memory as well as neural models of memory consolidation (e.g., hippocampal neural replay). Additionally, many studies examine a limited range of emotional stimuli and fail to disentangle differences in memory performance because of variance in valence and arousal. Here, we experimentally increase non-REM sleep features, sleep spindle density, and SWS, with pharmacological interventions using zolpidem (Ambien) and sodium oxybate (Xyrem) during daytime naps. We use a full spread of emotional stimuli to test all levels of valence and arousal. We find that increasing sleep spindle density increases memory discrimination (da) for highly arousing and negative stimuli without altering measures of bias (ca). These results indicate a broader role for sleep in the processing of emotional stimuli with differing effects based on arousal and valence, and they raise the possibility that sleep spindles causally facilitate emotional memory consolidation. These findings are discussed in terms of the known use of hypnotics in individuals with emotional mood disorders.

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Older people dying with dementia: a nationwide study

International Psychogeriatrics ◽

10.1017/s1041610212000865 ◽

2012 ◽

Vol 24 (10) ◽

pp. 1581-1591 ◽

Cited By ~ 27

Author(s):

Koen Meeussen ◽

Lieve Van den Block ◽

Michael Echteld ◽

Nicole Boffin ◽

Johan Bilsen ◽

...

Keyword(s):

Older People ◽

End Of Life ◽

Elderly People ◽

Cognitive Abilities ◽

End Of Life Care ◽

Large Scale ◽

Care Home ◽

Life Care ◽

Early Palliative Care ◽

People With Dementia

ABSTRACTBackground: Large-scale nationwide data describing the end-of-life characteristics of older people with dementia are lacking. This paper describes the dying process and end-of-life care provided to elderly people with mild or severe dementia in Belgium. It compares with elderly people dying without dementia.Methods: A nationwide retrospective mortality study was conducted, via representative network of general practitioners (GPs) in 2008 in Belgium, with weekly registration of all deaths (aged ≥ 65) using a standardized form. GPs reported on diagnosis and severity of dementia, aspects of end-of-life care and communication, and on the last week of life in terms of symptoms that caused distress as judged by the GP, and the patients’ physical and cognitive abilities.Results: Thirty-one percent of our sample (1,108 deaths) had dementia (43% mildly, 57% severely). Of those, 26% died suddenly, 59% in care home, and 74% received palliative treatment, versus 37%, 19%, and 55% in people without dementia. GP–patient conversations were less frequent among those with (45%) than those without (73%) dementia, and 11% of both groups had a proxy decision-maker. During the last week of life, physical and psychological distress was common in both groups. Of older people with dementia, 83% were incapable of decision-making and 83% were bedridden; both significantly higher percentages than found in the group without dementia (24% and 52%).Conclusions: Several areas of end-of-life care provision could be improved. Early communication and exploration of wishes and appointment of proxy decision-makers are important components of an early palliative care approach which appears to be initiated too infrequently.

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Modeling and Coordinated Control Strategy of Large Scale Grid-Connected Wind/Photovoltaic/Energy Storage Hybrid Energy Conversion System

Mathematical Problems in Engineering ◽

10.1155/2015/682321 ◽

2015 ◽

Vol 2015 ◽

pp. 1-14 ◽

Cited By ~ 5

Author(s):

Lingguo Kong ◽

Guowei Cai ◽

Sidney Xue ◽

Shaohua Li

Keyword(s):

Energy Storage ◽

Energy Conversion ◽

Hybrid System ◽

Control Strategy ◽

Large Scale ◽

Coordinated Control ◽

Hybrid Energy ◽

Conversion System ◽

Energy Conversion System ◽

Continuous Power

An AC-linked large scale wind/photovoltaic (PV)/energy storage (ES) hybrid energy conversion system for grid-connected application was proposed in this paper. Wind energy conversion system (WECS) and PV generation system are the primary power sources of the hybrid system. The ES system, including battery and fuel cell (FC), is used as a backup and a power regulation unit to ensure continuous power supply and to take care of the intermittent nature of wind and photovoltaic resources. Static synchronous compensator (STATCOM) is employed to support the AC-linked bus voltage and improve low voltage ride through (LVRT) capability of the proposed system. An overall power coordinated control strategy is designed to manage real-power and reactive-power flows among the different energy sources, the storage unit, and the STATCOM system in the hybrid system. A simulation case study carried out on Western System Coordinating Council (WSCC) 3-machine 9-bus test system for the large scale hybrid energy conversion system has been developed using the DIgSILENT/Power Factory software platform. The hybrid system performance under different scenarios has been verified by simulation studies using practical load demand profiles and real weather data.

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Sleep Spindles in the EEGs of Hyperactive Children

Psychological Reports ◽

10.2466/pr0.1987.60.1.139 ◽

1987 ◽

Vol 60 (1) ◽

pp. 139-144 ◽

Cited By ~ 8

Author(s):

Nancy A. Kiesow ◽

Walter W. Surwillo

Keyword(s):

Attention Deficit Disorder ◽

Chloral Hydrate ◽

Sleep Spindles ◽

Sleep Spindle ◽

Control Groups ◽

Cast Doubt ◽

Stage 2 Sleep ◽

Hyperactive Children ◽

And Control ◽

Theoretical Issues

Electroencephalograms (EEGs) of 11 boys, aged 3 to 11 yr., who had been diagnosed as Attention Deficit Disorder with Hyperactivity were compared with 11 controls matched for age and sex. The purpose was to determine whether there was any difference between the groups in the number of sleep spindles present during Stage 2 sleep. The EEGs of the subjects studied were typical of those performed in most clinical laboratories, with approximately 8 min. of daytime Stage 2 sleep recorded for each child. Most of the subjects in both groups were given Chloral Hydrate to induce sleep. The number of sleep spindles/sec. in Stage 2 sleep and the time spent in Stage 2 sleep were estimated for each subject, and means were obtained for both groups. Findings showed no statistically significant differences between hyperactive and control groups. The results cast doubt on the significance of sleep spindle activity in assessing hyperactivity or in resolving current theoretical issues relating to hyperactivity.

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