Sleep function: current questions and new approaches.

Center for Integrative Genomics, Génopode Building, University of Lausanne, Lausanne, Switzerland.
European Journal of Neuroscience (Impact Factor: 3.67). 06/2009; 29(9):1830-41. DOI: 10.1111/j.1460-9568.2009.06767.x
Source: PubMed

ABSTRACT The mammalian brain oscillates through three distinct global activity states: wakefulness, non-rapid eye movement (NREM) sleep and REM sleep. The regulation and function of these 'vigilance' or 'behavioural' states can be investigated over a broad range of temporal and spatial scales and at different levels of functional organization, i.e. from gene expression to memory, in single neurons, cortical columns or the whole brain and organism. We summarize some basic questions that have arisen from recent approaches in the quest for the functions of sleep. Whereas traditionally sleep was viewed to be regulated through top-down control mechanisms, recent approaches have emphasized that sleep is emerging locally and regulated in a use-dependent (homeostatic) manner. Traditional markers of sleep homeostasis, such as the electroencephalogram slow-wave activity, have been linked to changes in connectivity and plasticity in local neuronal networks. Thus waking experience-induced local network changes may be sensed by the sleep homeostatic process and used to mediate sleep-dependent events, benefiting network stabilization and memory consolidation. Although many questions remain unanswered, the available data suggest that sleep function will best be understood by an analysis which integrates sleep's many functional levels with its local homeostatic regulation.


Available from: Anne Vassalli, Apr 24, 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: In his pioneering research on the neural mechanisms of filial imprinting, Gabriel Horn has gone a long way to fulfilling Karl Lashley's dream of finding the 'engram' or memory trace in the brain. Here we review recent research into the engram(s) of song learning in songbirds, particularly zebra finches. When juvenile songbirds learn their songs from a tutor, they form and alter a central representation of the tutor song, known as the 'template'. Secondary auditory regions in the caudal medial pallium are likely to contain the neural substrate for the representation of tutor song, but the roles of the different regions remain to be elucidated. Female zebra finches do not sing, but nevertheless form an auditory memory of their father's song, for which the neural substrate is located in the caudomedial pallium. In males that are learning their songs, there is continual interaction between the secondary auditory regions and sensorimotor regions, similar to the interaction between Broca's and Wernicke's areas in human infants acquiring speech and language. Copyright © 2014. Published by Elsevier Ltd.
    Neuroscience & Biobehavioral Reviews 11/2014; 50. DOI:10.1016/j.neubiorev.2014.11.019 · 10.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Subcortical circuits mediating sleep-wake functions have been well characterized in animal models, and corroborated by more recent human studies. Disruptions in these circuits have been identified in hypersomnia disorders (HDs) such as narcolepsy and Kleine-Levin Syndrome, as well as in neurodegenerative disorders expressing excessive daytime sleepiness. However, the behavioral expression of sleep-wake functions is not a simple on-or-off state determined by subcortical circuits, but encompasses a complex range of behaviors determined by the interaction between cortical networks and subcortical circuits. While conceived as disorders of sleep, HDs are equally disorders of wake, representing a fundamental instability in neural state characterized by lapses of alertness during wake. These episodic lapses in alertness and wakefulness are also frequently seen in neurodegenerative disorders where electroencephalogram demonstrates abnormal function in cortical regions associated with cognitive fluctuations (CFs). Moreover, functional connectivity MRI shows instability of cortical networks in individuals with CFs. We propose that the inability to stabilize neural state due to disruptions in the sleep-wake control networks is common to the sleep and cognitive dysfunctions seen in hypersomnia and neurodegenerative disorders.
    Frontiers in Neurology 09/2014; 5:165. DOI:10.3389/fneur.2014.00165
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The phenomenological relationship between consciousness and sleep are reviewed. Consciousness has a self-reflexive component, and while sleeping that is not working as in awakenings. The necessity of some change in narrow concepts of conscious as to be aware and self reflective as well of some aspects of Altered State of Consciousness are ex-plained. In fact, in rapid eye movements [REM] sleep is the sleep stage in which some perception of consciousness is found self-perception in REM sleep is a common phenomenon, but to be aware of that is called lucid dreams. Also sleep paralysis produce some activation of self-awareness. The lack of continuity between cortical areas in delta sleep stages could explain the loss of consciousness is such sleep stage, which support the idea of cortical continuity as a necessary condition for to achieve this integrative process. A ques-tion that emerges after update the knowledge about sleep and consciousness is what is the minimum degree of connec-tivity and activity of the central nervous system for to be conscious? New paradigms in neurosciences like connectome and enactivation, removes reductionist approaches to the main -body issue. Enactive approach could be used as a paradigm to understand cognitive activity in three neurophysiology stages. As a proposal, it can be figured out as follows: (A) In wakefulness, the enactive phenomenon has priority to start whatever action is necessary. A biofeedback to make corrections in order to improve the motor programs, mind theory or any other active strategies; (B) In REM sleep in which there is not external stimuli. Those are generated from the sensorial nuclei in the brainstem which generates internal electrical activity that follows sensorial pathways [i.e., PGO waves] with visual and emotional targets [i.e., occipital visual cortex and amygdale complex] and probably without enactivation, but inner generating stimulation so the brain cortex is activated mainly by brainstem without any anticipatory top-down events; and (C) In delta sleep, in which there are no enactivation and no sensorial inputs, but also there is no interconnectivity in the brain cortex, which is a necessary condition for consciousness and memory. New technical tools as functional magnetic resonance, trans-cranial magnetic stimulation, and magnetic electroencephalo-graphy have open new approaches for develop feasible hypotheses in this field.
    The Open Sleep Journal 05/2011; 4(1). DOI:10.2174/1874620901104010001