Summary: One study reports that warm-blooded animals with higher body temperatures have less REM sleep, while those with lower body temperatures have more REM sleep. Researchers say that REM sleep acts as a “thermostatically controlled brain warmer.”
According to a new study by UCLA Professor Jerome Siegel, who said his study suggests that REM sleep acts as a “thermostatically controlled brain warmer”.
The study in Lancet Neurology suggests a previously unobserved relationship between body temperature and REM sleep, a period of sleep when the brain is highly active, said Siegel, who directs the Center for Sleep Research at the Jane and Terry Semel Institute. for Neuroscience and Human Behavior at UCLA.
Birds have the highest body temperature of any warm-blooded or homeothermic animal group at 41 degrees while getting the least REM sleep at 0.7 hours per day. Next come humans and other placental mammals (37 degrees, 2 hours REM sleep), marsupials (35 degrees, 4.4 hours REM sleep), and monotremes (31 degrees, 7.5 hours REM sleep).
Brain temperature drops during non-REM sleep and then rises during the REM sleep that usually follows. This model “allows warm-blooded mammals to conserve energy during non-REM sleep without the brain becoming so cold that it fails to respond to threat,” Siegel said.
The amount of REM sleep in humans is neither high nor low compared to other warm-blooded animals, “undermining some popular views suggesting a role for REM sleep in learning or emotional regulation,” he said. .
Funding: Siegel’s research is supported by grants from the National Institutes of Health (HLB148574 and DA034748) and the Department of Veterans Affairs Medical Research Service. He declared no competing interests.
About this sleep research news
Author: Jason Millman
Contact: Jason Millman – UCLA
Image: Image is in public domain
Original research: Free access.
“Sleep Function: An Evolutionary Perspective” by Jerome Siegel et al. Lancet Neurology
Sleep function: an evolutionary perspective
Prospective epidemiological studies in industrial societies indicate that 7 h of sleep per night in people aged 18 or over is optimal, with greater or lesser amounts of sleep predicting a shorter lifespan. Humans living a hunter-gatherer lifestyle (e.g. tribal groups) sleep 6-8 hours per night, with the longest sleep durations in winter.
The prevalence of insomnia in hunter-gatherer populations is low (about 2%) compared to the prevalence of insomnia in industrial societies (about 10-30%). Sleep deprivation studies, which are done to better understand sleep function, are often confounded by the effects of stress.
Considering spontaneous daily sleep duration in mammalian species, which ranges from 2 h to 20 h, can provide important insights into sleep function without the stress of deprivation.
Sleep duration is not related to brain size or cognitive ability. Rather, the sleep duration of species is associated with their ecological niche and food requirements, indicating a role of sleep-wake balance in food acquisition and energy conservation. Brain temperature drops from waking levels during non-rapid eye movement (non-REM) sleep and rises during REM sleep.
The average daily REM sleep time of homeothermal orders is negatively correlated with average body and brain temperature, with the greatest amount of REM sleep in egg-laying mammals (monotremes), moderate amounts in pouched mammals (marsupials) , lower amounts in placental mammals and the lowest amounts in birds.
REM sleep may therefore have a key role in regulating brain temperature and metabolism during sleep and in facilitating alert waking.
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