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Why do we sleep? The answer may change right before we turn 3.:
Humans spend about a third of our lives sleeping, and scientists have long debated why slumber takes up such a huge slice of our time. Now, a new study hints that our main reason for sleeping starts off as one thing, then changes at a surprisingly specific age.
Two leading theories as to why we sleep focus on the brain: One theory says that the brain uses sleep to reorganize the connections between its cells, building electrical networks that support our memory and ability to learn; the other theory says that the brain needs time to clean up the metabolic waste that accumulates throughout the day. Neuroscientists have quibbled over which of these functions is the main reason for sleep, but the new study reveals that the answer may be different for babies and adults.
In the study, published Sep. 18 in the journal Science Advances, researchers use a mathematical model to show that infants spend most of their sleeping hours in "deep sleep," also known as random[sic] eye movement (REM)[*] sleep, while their brains rapidly build new connections between cells and grow ever larger. Then, just before toddlers reach age 2-and-a-half, their amount of REM sleep dips dramatically as the brain switches into maintenance mode, mostly using sleep time for cleaning and repair.
[...] The study authors built a mathematical model to track all these shifting data points through time and see what patterns emerged between them. They found that the metabolic rate of the brain was high during infancy when the organ was building many new connections between cells, and this in turn correlated with more time spent in REM sleep. They concluded that the long hours of REM in infancy support rapid remodeling in the brain, as new networks form and babies pick up new skills. Then, between age 2 and 3, "the connections are not changing nearly as quickly," and the amount of time spent in REM diminishes, Savage said.
[...] "In the first few years of life, you see that the brain is making tons of new connections ... it's blossoming, and that's why we see all those skills coming on," Tarokh said. Developmental psychologists refer to this as a "critical period" of neuroplasticity — the ability of the brain to forge new connections between its cells. "It's not that plasticity goes away" after that critical period, but the construction of new connections slows significantly, as the new mathematical model suggests, Tarokh said. At the same time, the ratio of non-REM to REM sleep increases, supporting the idea that non-REM is more important to brain maintenance than neuroplasticity.
[*] Wikipedia: Rapid eye movement sleep:
Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.
Journal Reference:
Junyu Cao, Alexander B. Herman, Geoffrey B. West, et al. Unraveling why we sleep: Quantitative analysis reveals abrupt transition from neural reorganization to repair in early development [open], Science Advances (DOI: 10.1126/sciadv.aba0398)
Previously:
(2020-06-08) Researchers Identify Neurons Responsible for Memory Consolidation During REM Sleep
(Score: 2) by looorg on Monday September 28 2020, @04:30PM (3 children)
The only thing I know is that the older I get the weirder my sleep becomes, I used to be able to sleep non-stop for the entire sleep cycle but the older I get the more chopped into little naps it becomes. I can't even recall the last time I slept 6-8h in a row. About 3-4h is now the max it seems. Usually I can just roll over and go back to sleep again but some times I feel fine, go up and do stuff for a few hours and then take another nap later on when I get tired again.
(Score: 4, Interesting) by bzipitidoo on Monday September 28 2020, @05:00PM (2 children)
Funny thing is, the 8 hours of sleep may be the weird thing, and shorter sleep periods the norm. With the advent of artificial lighting, we've forgotten how sleep used to be. Think about it. The average length of a night is 12 hours. Even if you shave an hour from each end under the thinking that shortly before sunrise and for a short while after sunset, there is enough light for a person to see to work, that's still 10 hours of darkness in which the light is just plain inadequate for us to do much. We don't need 10 hours of sleep every night. Also, did you ever wonder how a watch-- that is, of course, someone "taking a watch", to look out for danger while everyone else sleeps, rather than a digital wristwatch kind of thing-- how a watch works? Was everyone not getting enough sleep, to cover the watches?
So, what did people do? Sleep for 10 hours each night? No. It was sleep for 4 hours, then 2 hours of quiet wakefulness, then 4 more hours of sleep, called the second sleep.
(Score: 2) by JoeMerchant on Monday September 28 2020, @05:10PM
The time between first and second sleep was frequently used to visit the facilities...
Україна досі не є частиною Росії Слава Україні🌻 https://www.pravda.com.ua/eng/news/2023/06/24/7408365/
(Score: 0) by Anonymous Coward on Tuesday September 29 2020, @07:21PM
There is no such thing as 12h average night if you live in northern areas, you might not get any night at all or it is 18h or more from sunset to sunrise. Yes it might average over a year but you will not experience it.
(Score: 2) by Immerman on Monday September 28 2020, @04:35PM (1 child)
Don't know who made the error, but what I recall, and a quick search confirms, is that deep sleep is the final stage of non-REM sleep, while REM sleep is almost identical to being awake.
(Score: 2) by JoeMerchant on Monday September 28 2020, @05:18PM
EEG sleep staging is inconsistent voodoo witch doctor practice. Take 10 sleep records to be scored by four well respected independent "Sleepologists" and you will get four different scorings back for each record 10/10. REM is commonly referred to as active dream sleep, it tends to be the last stage of sleep entered before regressing toward wakefulness. It's that time when your brain is engaged in imaginative activity, but your motor centers have been -mostly- deactivated so you don't usually flail around, except the eye pointing muscles seem to not be disabled the way the rest of the body is, thus: REM.
All rules and patterns have exceptions. While some call REM the "deepest" sleep, it does most closely resemble wakefulness on an EEG trace.
Fun fact: most of what EEG reads for "mind control" devices is actually EMG - muscle activation artifacts. The "brain waves" are in there, but the successful EEG controlled widgets mostly ignore brain waves for conscious control of stuff. Even REM is usually discriminated by electrodes that look at eye muscle activity.
Україна досі не є частиною Росії Слава Україні🌻 https://www.pravda.com.ua/eng/news/2023/06/24/7408365/
(Score: 0) by Anonymous Coward on Monday September 28 2020, @05:28PM
Or, I ran out of diesel to add to my coffee.
(Score: 2) by DannyB on Monday September 28 2020, @05:48PM
I sleep when I get tired of staring at code*.
But I make sure I have an alarm set so I wake up on time.
Beep! Hey, it's 5 PM, wake up! Quitting time!
*Java
Is there a chemotherapy treatment for excessively low blood alcohol level?
(Score: 3, Funny) by EJ on Monday September 28 2020, @06:42PM
As babies, we are taught that there are three periods in life: Playtime, mealtime, and nap time.
As adults, we recognize that it is neither playtime nor mealtime, so it must be nap time. This is why adults sleep.