Is Sleep Essential?

Cirelli, Chiara; Tononi, Giulio

doi:10.1371/journal.pbio.0060216

Cited by 555 publications

(458 citation statements)

References 88 publications

(114 reference statements)

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“…In addition, such long-lasting flights raise the question of how or whether these birds sleep. For many decades sleep has been considered as an unavoidable necessity to restore at least some of the physiological functions of the brain 24 . In Alpine swifts there seems to be no necessity for physical inactivity to maintain any of the relevant physiological processes.…”

Section: Discussionmentioning

confidence: 99%

First evidence of a 200-day non-stop flight in a bird

et al. 2013

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Being airborne is considered to be energetically more costly as compared with being on the ground or in water. Birds migrating or foraging while airborne are thought to spend some time resting on the ground or water to recover from these energetically demanding activities. However, for several decades ornithologists have claimed that some swifts may stay airborne for almost their whole lifetime. Here we present the first unequivocal evidence that an individual bird of the Alpine swift (Tachymarptis melba) can stay airborne for migration, foraging and roosting over a period of more than 6 months. To date, such long-lasting locomotive activities had been reported only for animals living in the sea. Even for an aerodynamically optimized bird, like the Alpine swift, flying requires a considerable amount of energy for continuous locomotive control. Our data imply that all vital physiological processes, including sleep, can be perpetuated during flight.

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Section: Discussionmentioning

confidence: 99%

First evidence of a 200-day non-stop flight in a bird

et al. 2013

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“…Cogent arguments against this possibility were discussed previously. 18,43,44 Other ideas about the functions of sleep are of two kinds: (i) molecular-level and metabolic conjectures; (ii) hypotheses with key assumptions at higher than molecular levels, for example, specific alterations in the strength of synaptic connections or other modifications of neuronal circuits.…”

Section: Introductionmentioning

confidence: 99%

Augmented generation of protein fragments during wakefulness as the molecular cause of sleep: a hypothesis

Varshavsky

2012

Protein Science

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Despite extensive understanding of sleep regulation, the molecular-level cause and function of sleep are unknown. I suggest that they originate in individual neurons and stem from increased production of protein fragments during wakefulness. These fragments are transient parts of protein complexes in which the fragments were generated. Neuronal Ca 21 fluxes are higher during wakefulness than during sleep. Subunits of transmembrane channels and other proteins are cleaved by Ca 21 -activated calpains and by other nonprocessive proteases, including caspases and secretases. In the proposed concept, termed the fragment generation (FG) hypothesis, sleep is a state during which the production of fragments is decreased (owing to lower Ca 21 transients) while fragment-destroying pathways are upregulated. These changes facilitate the elimination of fragments and the remodeling of protein complexes in which the fragments resided. The FG hypothesis posits that a proteolytic cleavage, which produces two fragments, can have both deleterious effects and fitness-increasing functions. This (previously not considered) dichotomy can explain both the conservation of cleavage sites in proteins and the evolutionary persistence of sleep, because sleep would counteract deleterious aspects of protein fragments. The FG hypothesis leads to new explanations of sleep phenomena, including a longer sleep after sleep deprivation. Studies in the 1970s showed that ethanol-induced sleep in mice can be strikingly prolonged by intracerebroventricular injections of either Ca 21 alone or Ca 21 and its ionophore (Erickson et al., Science 1978;199:1219-1221 Harris, Pharmacol Biochem Behav 1979;10:527-534; Erickson et al., Pharmacol Biochem Behav 1980;12:651-656). These results, which were never interpreted in connection to protein fragments or the function of sleep, may be accounted for by the FG hypothesis about molecular causation of sleep.

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“…From an evolutionary standpoint, sleep appears to be both ancient and pervasive across the animal kingdom[1,2]. Although the functions of sleep are currently poorly understood[3,4,5], a growing body of literature suggests a role for sleep in memory consolidation[6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

Integrated Brain Circuits: Neuron-Astrocyte Interaction in Sleep-Related Rhythmogenesis

Halassa

Maschio²,

Beltramo³

et al. 2010

The Scientific World JOURNAL

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Although astrocytes are increasingly recognized as important modulators of neuronal excitability and information transfer at the synapse, whether these cells regulate neuronal network activity has only recently started to be investigated. In this article, we highlight the role of astrocytes in the modulation of circuit function with particular focus on sleep-related rhythmogenesis. We discuss recent data showing that these glial cells regulate slow oscillations, a specific thalamocortical activity that characterizes non-REM sleep, and sleep-associated behaviors. Based on these findings, we predict that our understanding of the genesis and tuning of thalamocortical rhythms will necessarily go through an integrated view of brain circuits in which non-neuronal cells can play important neuromodulatory roles.

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Is Sleep Essential?

Abstract: No current hypothesis can explain why animals need to sleep. Yet, sleep is universal, tightly regulated, and cannot be deprived without deleterious consequences. This suggests that searching for a core function of sleep, particularly at the cellular level, is still a worthwhile exercise.

Cited by 555 publications

References 88 publications

First evidence of a 200-day non-stop flight in a bird

First evidence of a 200-day non-stop flight in a bird

Augmented generation of protein fragments during wakefulness as the molecular cause of sleep: a hypothesis

Integrated Brain Circuits: Neuron-Astrocyte Interaction in Sleep-Related Rhythmogenesis

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