Why we sleep: the evolutionary pathway to the mammalian sleep

Nicolau, M.C.; Akaârir, Mourad; Gamundı́, Antoni; González, José M.; Rial, Rubén V.

doi:10.1016/s0301-0082(00)00013-7

Cited by 70 publications

(34 citation statements)

References 96 publications

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“…Although one cannot differentiate between sleep stages or assess sleep intensity with videotapes, one can assess the basic temporal distribution of behavioral sleep across a 24-h period. The sleep state is typically marked by several easily observed behaviors, including adoption of a species-specific sleep posture with the eyes closed (Campbell and Tobler, 1984;Nicolau et al, 2000). Thus, for each 5-min bin, we scored an animal as having been behaviorally asleep only if, for the entire period, its eyes were closed as it either lay on its side or sat curled up with the head tucked into the body and if it made no movement other than very slight and brief transitional changes in posture.…”

Section: Behavioral Sleep Data Collectionmentioning

confidence: 99%

Individual Differences in Rhythms of Behavioral Sleep and Its Neural Substrates in Nile Grass Rats

Schwartz

Smale

2005

J Biol Rhythms

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Laboratory populations of grass rats (Arvicanthis niloticus) housed with a running wheel show considerable variation in patterns of locomotor activity. At the extremes are "day-active" (DA) animals with a monophasic distribution of running throughout the light phase and "night-active" (NA) animals exhibiting a biphasic pattern with an extended peak at the beginning of the dark phase and a brief peak shortly before lights-on. Here, the authors use this intraspecific variation to explore interactions between circadian and homeostatic influences on sleep and the effects of these interactions on the activity of brain regions involved in sleep regulation. Male animals were singly housed with running wheels in a 12:12 LD cycle, videotaped for 24 h, and perfused at ZT 4 or 16. Behavioral sleep was scored from the videotapes, and brains were processed for cFos immunoreactivity (cFos-ir). Sleep duration within the light and dark phases was higher in NA and DA animals, respectively, but these groups did not differ with respect to total sleep. In both groups, sleep bouts were shortest in the light phase and longest between ZT 20 and ZT 23. In the ventrolateral preoptic area (VLPO), cFos-ir was higher at ZT 16 than at ZT 4 in DA but not NA grass rats, and it was correlated with behavioral sleep at ZT 16 but not ZT 4. In OXA neurons, cFos-ir was high at ZT 4 in DA grass rats and at ZT 16 in NA grass rats, and it was correlated with behavioral sleep at both times. In the lower subparaventricular zone (LSPV), cFos-ir was higher at ZT 16 in both DA and NA animals, and it was unrelated to behavioral sleep. Thus, patterns of cFos-ir in the LSPV and OXA neurons were most tightly linked to time and sleep, respectively, whereas cFos-ir in the VLPO was influenced by an interaction between these 2 variables.

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Section: Behavioral Sleep Data Collectionmentioning

confidence: 99%

Individual Differences in Rhythms of Behavioral Sleep and Its Neural Substrates in Nile Grass Rats

Schwartz

Smale

2005

J Biol Rhythms

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“…Mammalian sleep has been physiologically divided into non-rapid eye movement sleep (NREM), occupied mostly by slow wave sleep (SWS) and rapid eye movement sleep (REM) [Nicolau et al, 2000;Zepelin et al, 2005;Cirelli and Tononi, 2008;Lesku et al, 2008;Siegel, 2008]. No consensus has been reached as to the functions of REM and NREM, but one avenue towards understanding these functions is an examination of how sleep amounts vary across species with differing physiological and ecological specializations [Tobler, 2005;Zepelin et al, 2005;Siegel, 2008;Horne, 2009;Rial et al, 2010].…”

Section: Introductionmentioning

confidence: 99%

Sleep in the Rock Hyrax, <i>Procavia capensis</i>

Gravett

Bhagwandin²,

Lyamin³

et al. 2012

Brain Behav Evol

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We investigated sleep in therock hyrax, Procavia capensis, a social mammal that typically lives in colonies on rocky outcrops throughout most parts of Southern Africa. The sleep of 5 wild-captured, adult rock hyraxes was recorded continuously for 72 h using telemetric relay of signals and allowing unimpeded movement. In addition to waking, slow wave sleep (SWS) and an unambiguous rapid eye movement (REM) state, a sleep state termed somnus innominatus (SI), characterized by low-voltage, high-frequency electroencephalogram, an electromyogram that stayed at the same amplitude as the preceding SWS episode and a mostly regular heart rate, were identified. If SI can be considered a form of low-voltage non-REM, the implication would be that the rock hyrax exhibits the lowest amount of REM recorded for any terrestrial mammal studied to date. Conversely, if SI is a form of REM sleep, it would lead to the classification of a novel subdivision of this state; however, further investigation would be required. The hyraxes spent on average 15.89 h (66.2%) of the time awake, 6.02 h (25.1%) in SWS, 43 min (3%) in SI and 6 min (0.4%) in REM. The unambiguous REM sleep amounts were on average less than 6 min/day. The most common state transition pathway in these animals was found to be wake → SWS → wake. No significant differences were noted with regard to total sleep time, number of episodes and episode duration for all states between the light and dark periods.Thus, prior classification of the rock hyrax as strongly diurnal does not appear to hold under controlled laboratory conditions.

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“…The purpose of sleep is not fully understood, but there is evidence that several processes are involved. These include restitution and rehabilitation, energy conservation, cognitive processing (including memory consolidation, brain reorganization and rebuilding) and, furthermore, sleep quality has an effect on life expectancy [14][15][16]. Thus, sleep is fundamental and essential to well-being and daytime functioning.…”

Section: Discussionmentioning

confidence: 99%