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The Memory Cognitive and,Psychological Functions of Sleep. Update from Electroencephalographic,and Neuroimaging Studies. Roumen Kirov1 and Serge Brand2,1Institute,of Neurobiology Bulgarian Academy of Sciences. 2Depression Research Unit Psychiatric Hospital of the University of Basel. 2Switzerland,1 Introduction, Sleep is a universal biological feature in almost all if not in all species and represents a. global state of immobility with greatly reduced responsiveness to environmental stimuli. which can be distinguished from coma or anaesthesia by its rapid reversibility Cirelli. Tononi 2008 It is by no means a dormant state When it is prevented the body tries to. recover the lost amount The existence of sleep rebound after deprivation reveals that sleep. is not simply a period of reduced activity or alertness regulated by circadian or ultradian. rhythms Dinges et al 2005 Notably in most vertebrates and all mammal species. including man sleep displays a specific architecture roughly described as a cyclic. occurrence of rapid eye movement REM sleep and non REM sleep Further dramatic. changes in brain electrophysiology neurochemistry and functional anatomy biologically. distinguish the different sleep stages from one another Hobson Pace Schott 2002 Pace. Schott Hobson 2002 Also human and animal neurophysiologic studies have shown that. the magnitude of changes in brain metabolism and neuronal activity in many discrete brain. structures during certain sleep stages exceeds that during most of the waking periods. Gottesmenn 1999 Maquet et al 1996 Nofzinger et al 1997 Steriade Timofeev 2003. Although the precise functions of sleep are still beyond comprehensive understanding. Cirelli Tononi 2008 many studies point to the critical role of sleep for physiological. functioning and adaptation Its vital importance is well documented by the fact that its. deprivation in rodents and flies can cause death more quickly relative to food deprivation. Rechtschaffen 1998 Thus sleep is shown to serve many energetic and metabolic immune. thermoregulatory cardiovascular and respiratory functions all responsible for normal. brain and body homeostasis Siegel 2009 Tononi Cirelli 2006 Notably along with these. functions sleep is shown to play a key role for important cognitive and psychological. processes among which learning and memory have been most intensively studied. Diekelmann Born 2010 Rasch Born 2007 Stickgold 2005 Walker 2008 Walker. Stickgold 2006 2010 Accordingly an extensive body of research has revealed a cruicial. www intechopen com, 156 Neuroimaging Cognitive and Clinical Neuroscience.
role for sleep in human cognitive abilities Mander et al 2008 Schabus et al 2006 2008. Yoo et al 2007b heuristic creativity and insightfulness Cai et al 2009 Stickgold et al. 1999 2001 Wagner et al 2004 Yordanova et al 2008 2009 2010 constructive thinking and. decision making Durrant et al 2011 Venkatraman et al 2011 and emotional regulation. Walker 2009 Walker van der Helm 2009 The latter engages consolidation of emotional. memory Nishida et al 2009 Wagner et al 2001 2006 Walker 2009 and emotional. processing Gujar et al 2011a 2011b Yoo et al 2007a Collectively these various. associations suggest that sleep provides unique conditions for off line memory. consolidation reconsolidation and information reprocessing to take place However it is. still not precisely known whether these mechanisms are distinctly different from the. restoring and energetic functions of sleep whether the two types of functions are coupled. or whether the latter simply facilitate the cognitive functions of sleep. Many electroencephalographic EEG and neuroimaging studies including functional. magnetic resonance imaging fMRI have found that the structural and functional. organization of the neural substrate undergoes changes during sleep in relation to human. cognition The entity of neural mechanisms underpinning cognitive and psychological. functions of the brain is generally recognized as brain plasticity i e as the capability of the. neural substrate to reorganize over time as a result of previous experiences In this chapter. studies demonstrating that sleep affects cognition by neural plasticity mechanisms in. humans will be updated and overviewed to provide a converging framework for better. understanding the role of sleep for memory cognitive abilities and psychological. functioning Since mechanisms of brain plasticity are closely related to sleep physiology. architecture and neurobiological regulation the reader will be first introduced to. neurobiology of sleep,2 Neurobiology of sleep,2 1 Sleep architecture and physiology. The heterogeneous nature of sleep can be seen in human and in most animal. polysomnographic PSG records which traditionally use electrophysiological techniques. including electroencephalography EEG electromyography EMG and electro. oculography EOG to characterize sleep at system levels In humans overnight sleep is. characterized by a cyclic occurrence of non REM sleep and REM sleep Non REM sleep. includes lighter sleep stages 1 and 2 and stages 3 and 4 of the deeper slow wave sleep SWS. Rechtschaffen Kales 1968 Whereas SWS dominates the first half of the night REM sleep. and stage 2 of non REM sleep dominate the second half This ultradian dynamics reflects the. circadian regulation of sleep that is distinguishable from its homeostatic regulation seen. after sleep deprivation or prolonged wakefulness Borb ly 1982 Borb ly Ackermann. 1999 Normally sleep onset begins with a brief period of stage 1 of non REM sleep which is. subsequently followed by sleep deepening marked by appearance of stage 2 of non REM. sleep and a further progressive transition to stages 3 and 4 of SWS The latter is followed by. a relatively short transient of stage 2 of non REM sleep after which a period of REM sleep. appears This progression of sleep stages and in particular the non REM sleep REM sleep. alternation forms one sleep cycle with approximately 90 min duration About 5 or more. such sleep cycles are usually observed in the normal human overnight sleep Broughton. 1987 Rechschaffen Kales 1968 Sinton McCarley 2000,www intechopen com. The Memory Cognitive and Psychological Functions of Sleep. Update from Electroencephalographic and Neuroimaging Studies 157. 2 2 Electrophysiological signatures of sleep stages. The distinct sleep stages of either human overnight sleep or human daily naps can be. determined by their specific macroscopic electrophysiological signatures which are. described by Rechschaffen Kales 1968 and are commonly used for human sleep stages. scoring Unlike the desynchronized mode of EEG activity during wakefulness the. electrophysiological signatures of different sleep stages are more complex which reflects a. more heterogeneous nature of sleep than that of wake Hobson Pace Schott 2002. Basically wakefulness is divided into active wake characterized by desynchronized low. voltage fast EEG activity including beta 15 30 Hz and gamma 30 Hz rhythms as well. as by theta 5 Hz EEG activity with frontal midline location and quiet wake. characterized by posterior alpha 10 Hz and central sigma 12 14 Hz EEG rhythms that. replace the desynchronized EEG mode of the active wake Niedermeyer 1993 The. electrophysiological signatures of both active and quiet are show in Figure 1. Sleep initiation is described as a replacement of waking EEG by theta or slower rhythms. paralleled by an appearance of very slow circular eye movements and both. electrophysiological features form stage 1 of non REM sleep Broughton 1987 Sinton. McCarley 2000 Stage 2 of non REM sleep is defined by presence of the classical EEG sleep. spindles oscillating at 12 15 Hz with central parietal location slower sleep spindles. oscillating at 9 13 Hz with frontal location and sporadic biphasic slow waves known as K. complexes Anderer et al 2001 De Gennaro Ferrara 2003 Sleep spindles are present. also in the deeper SWS stages but in less pronounced and discrete forms among which. spindle activity in the frequency range of 8 12 Hz with frontal location is recognized to. dominate SWS Cantero et al 2002 Salih et al 2009 K complexes are regarded as. precursors of EEG components of the SWS Amzica Steriade 1997 De Gennaro Ferrara. 2003 These macroscopic human electrophysiological signatures of distinct sleep wake. stages are shown in Figure 1, SWS is hallmarked by synchronous high voltage 75 V EEG delta 1 4 Hz waves and. slow 1 Hz oscillations SO Achrermann Borbely 1997 Crunelli Hughes 2010. Steriade et al 1993 both recognized as slow wave activity SWA Fig 1 SO are also. shown to occur in stage 2 of non REM sleep Crunelli Hughes 2010 Nir et al 2011 and. the SO during both stage 2 of non REM sleep and SWS are shown to group and synchronize. sleep spindles and delta waves M lle et al 2002 M lle et al 2004 Steriade 2001 Whereas. sleep spindles originate form interactions between thalamo cortical circuits involving. aminobutyric GABA ergic thalamic neurons and glutamate ergic cortical neurons De. Gennaro Ferrara 2003 Steriade 2006 SO are shown to have a neocortical origin. Achrermann Borbely 1997 Nir et al 2011 Steriade et al 1993 although they are also. proposed to emerge form the thalamus Crunelli Hughes 2010 Another important EEG. signature of SWS seen not only in animals but also in human intracranial EEG recordings is. reflected by hippocampal sharp wave ripple SWR bursts Hippocampal sharp waves. generated in the hippocampal CA3 region are fast depolarizing events on which high. frequency oscillations 80 200 Hz originating from an interaction between inhibitory. interneurons and pyramidal cells in CA1 so called ripples are superimposed Buzs ki. 2006 Csicsvari et al 1999 Notably SO have been shown to group also SWR in rodents. Battaglia et al 2004 Sirota et al 2003 and a temporal phase coupling between SO sleep. spindles and SWR has been demonstrated in human depth EEG records during SWS. Clemens et al 2007 2011 Nir et al 2011 The complex relationship between these sleep. signatures is regarded as reflecting brain plasticity mechanisms at a system level which is. www intechopen com, 158 Neuroimaging Cognitive and Clinical Neuroscience. important for the memory consolidation and reconsolidation during SWS Diekelmann. 100 V 100 V,100 V 100 V,100 V 100 V,100 V 100 V,100 V 100 V.
100 V 100 V,Active Wake Quiet Wake,100 V 100 V,100 V 100 V. 100 V 100 V,100 V 100 V,100 V 100 V,100 V 100 V,Stage 1 of non REM Sleep Stage 2 of non REM Sleep. Slow Wave Sleep REM Sleep, Fig 1 Electrophysiological signatures of distinct sleep wake stages EEG recorded from Fz. Cz and Pz vertical v and horizontal h eye movements and electromyogram m. Calibration marks are set up at 100 V time horizontal marks are 1 s. Unlike non REM sleep electrophysiology REM sleep EEG signatures Fig 1 include low. voltage desynchronized wake like EEG activity comprising theta and fast beta and gamma. rhythms accompanied by a swift occurrence of rapid eye movements REM upon lack of. muscle tone Aserinsky Kleitman 1953 Cantero et al 2003 Clemens et al 2009. Hippocampal theta rhythm is a prominent REM sleep EEG signature in rodents. Gottesmann 1999 Kirov Moyanova 2002 and felines Hobson Pace Schott 2002. while in human hippocampus and neocortex it is less coherent Cantero et al 2003. Further REM sleep is hallmarked by ponto geniculo occipital PGO waves PGO waves are. driven by intense bursts of synchronized activity that propagate from the pontine brainstem. mainly to the lateral geniculate nucleus and visual cortex Callaway et al 1987 Hobson. Pace Schott 2002 Pace Schott Hobson 2002 They occur in temporal association with. www intechopen com, The Memory Cognitive and Psychological Functions of Sleep. Update from Electroencephalographic and Neuroimaging Studies 159. REM in rats and felines Callaway et al 1987 Stickgold et al 2001 as well as in humans. Lim et al 2007 Miyauchi et al 2009 and are suggested to reflect both dream mental states. of REM sleep and cognitive processing during this sleep stage Stickgold et al 2001 REM. sleep signatures are shown to reflect mechanisms of brain plasticity at synaptic and genetic. levels Ribeiro et al 1999 2002 which may promote not only REM sleep specific processes. but also a further transformation of consolidated memories Walker Stickgold 2010. 2 3 Mechanisms of sleep regulation, The regulation of sleep is active in its own rights and is closely related to sleep s physiology.
and functions Hobson 2005 Pace Schott Hobson 2002 The respective neurobiological. mechanisms are represented by complex reciprocal interactions between different neuronal. populations and their chemical modulators and transmitters in distinct functional states. across sleep wake cycle leading to distinct functional states Gottesmann 1999 Hobson et. al 1975 Hobson Peace Schott 2002 Peace Schott Hobson 2002 Two major brain. regions are mostly considered in sleep regulation especially when functions of sleep are. concerned Pace Schott Hobson 2002 The first engages neuronal populations located in. the diencephalon in particular the hypothalamus mostly involved in the circadian. regulation of sleep The second brain region engages brainstem or meso pontine and basal. forebrain nuclei spread in the reticular ascending system RAS and projecting. noradrenaline NA serotonin 5 Hydroxytryptamine 5 HT and acetylchol. Tononi 2008 It is by no means a dormant state When it is prevented the body tries to recover the lost amount The existence of sleep rebound after deprivation reveals that sleep is not simply a period of reduced activity or alertness regulated by circadian or ultradian rhythms Dinges et al 2005 Notably in most vertebrates and all

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