
Researchers suggest that R.E.M. sleep serves to warm the brain - dnetesn
https://www.nytimes.com/2018/06/07/science/seals-mammals-sleep-brain.html
======
yosito
So the hypothesis is that mammals need REM sleep to prevent the brain from
getting too cold while sleeping, but the hypothesis hasn't been tested yet.

If this turns out to be true, I wonder if it has implications for night
terrors. It seems plausible that if the brain fails to warm enough through REM
sleep, hormones are released to wake the brain up completely which lead to
night terrors and the adrenaline rush feeling that accompanies them.

These are just hypotheses, but interesting nonetheless.

~~~
tim333
The hypothesis seems a little unlikely. If REM sleep was to warm up the brain
you might think people wouldn't do it in hot climates but I don't think that's
the case.

Maybe it's more like the "Google’s DeepMind AI gives robots the ability to
dream" stuff that increased their neural nets rate of learning 10x
[https://www.extremetech.com/extreme/240163-googles-
deepmind-...](https://www.extremetech.com/extreme/240163-googles-deepmind-ai-
gives-robots-ability-dream) and "Rats Dream About the Places They Want to
Explore"
[https://news.ycombinator.com/item?id=9791927](https://news.ycombinator.com/item?id=9791927)
\- about improved cognition.

Also the 'inceptionism' stuff looks so reminiscent of human dreams that it
makes me suspect there is neural network stuff going on rather than heating.
[https://news.ycombinator.com/item?id=9736598](https://news.ycombinator.com/item?id=9736598)

~~~
untog
> If REM sleep was to warm up the brain you might think people wouldn't do it
> in hot climates but I don't think thats the case.

Isn't internal body temperature kept constant (or at least the body tries very
hard to) irrespective of environment?

~~~
tim333
The body tries to keep the core temperature constant around the heart and
internal organs and will divert blood there and let your feet get cold. I'm
not sure about the brain but in a 40C climate say I doubt your head would get
cold inside.

~~~
gpvos
Depends on where you are. In a land climate, days can be searing hot while
nights are freezing cold.

~~~
CydeWeys
There's plenty of places in the tropics where it's hot during the day and
night for months on end, and yet as far as I know there's no evidence of less
REM sleep in the people living there. And even if there weren't, these
conditions would be easy to replicate in a laboratory.

------
weliketocode
I know a very successful banker who prides himself on sleeping 4 hours a night
because he believes that is the optimal point where each additional hour no
longer has any incremental benefit.

I have gone through periods of high and low amounts of sleep for both work and
personal reasons.

Sleep has always been phrased in terms of time - ie get x hours of
uninterrupted sleep to perform your best. But there has to be more to it than
that.

I've stayed up all night and felt rejuvenated the next day. And I've had lazy
Sundays where I've remained tired the entire day.

I might not have not seen the scientific study on it yet, but I believe the
quality of your sleep has a lot to do with the nature of when and why you're
sleeping as well as your mental state when doing so.

~~~
arthurofbabylon
In the traditional medicine system of India (Ayurveda), there is an anecdote
passed around that goes something like this: for each hour of sleep before
midnight, count it as two hours. For each hour of sleep between midnight and
sunrise, count it as one hour. Sleeping after sunrise counts for zero - it is
useless.

And I've observed this to be true in my life. The most peaceful, restful sleep
I experience is consistently between 10pm and 1am.

I fully agree with your dismissal of hours slept being the quantitative unit
of sleep, and I'm similarly curious about what constitutes a healthy,
effective sleep habit...

~~~
crazygringo
> _Sleeping after sunrise counts for zero - it is useless._

I don't know about some people, but for me this is practically the silliest
thing I've ever heard.

I need 8 hrs of sleep period, and the time of day has _zero_ effect on my
alertness. It can be 9pm-5am or 3am-12pm, it's exactly the same.

But if I get only 6 hrs of sleep? I'm miserable.

I can't even begin to imagine where the idea that the hour of the day matters
would have come from.

And just think of nighttime workers. Obviously their daytime sleep counts...

~~~
leonroy
> And just think of nighttime workers. Obviously their daytime sleep counts...

I think the quote is more an aphorism than rigorous guide. The framers of the
quote probably didn’t anticipate the night shift ;)

~~~
SmellyGeekBoy
It's interesting to consider that the 9-5 workday is a very modern innovation,
especially considering how long Ayurveda has been around.

------
daxfohl
If it's related to warmth, then why would rats have to make it up after days
of deprivation? Overheating seems like it would be just as destructive.

------
dpods
I'd recommend the book "The Promise of Sleep" [0] for anyone that's interested
in learning more about sleep. The author basically pioneered the sleep
medicine field and was at the University of Chicago in 1951 when R.E.M. sleep
was discovered.

[0]: [https://www.amazon.com/Promise-Sleep-Medicine-Connection-
Hap...](https://www.amazon.com/Promise-Sleep-Medicine-Connection-
Happiness/dp/0440509017)

~~~
toomuchtodo
Thanks, purchased!

Sidenote: The book recommendations on HN are always top notch.

------
startupdiscuss
You know my performance might change imperceptibly with sleep, but the area
where I know it makes a difference -- probably the most important area -- is
how nice I am to fellow human beings.

I am a better co-worker, family member, client etc with sleep.

They should look at aggression in animals rather than how well they do tasks.

------
ndh2
What is the connection between swimming and heat? How did they even arrive at
this hypothesis? Why would rats need to catch up on heating their brains, days
after missing REM sleep?

The facts are interesting, the conclusion doesn't make any sense at all to me.

~~~
ekr
It doesn't make any sense at all to me either. Because of the difference in
specific heat and heat conductivity of water vs air, an animal that can sleep
under-water (even whilst alternating the sleeping part of their brain), surly
doesn't need to warm its brain while on sleeping on land.

(But I'm no expert.)

~~~
lopmotr
It could be that the cooling of the brain is dominated by convection through
blood flow rather than conduction through the skull/fat/skin. If that's true,
then the effect of water vs air would be on the whole body which still has to
be maintained at proper body temperature so there would be no difference in
brain temperature sleeping the same way in water or in air. If the body's
temperature regulation is designed assuming that the brain is always
generating too much of its own heat and doesn't need to be supplied with
additional heat like the extremities do, then, it would still need to keep up
that heat generation independently of the rate of heat loss to the
environment.

------
Smaug123
My first reaction was that it seems so _inefficient_ to bring the entire
computer online just to maintain its temperature - which could be controlled
physically using blood. But couldn't we test this by artificially keeping the
brain warm and seeing what sleep patterns emerge?

~~~
creep
As an anecdote, I always have intense dreams with fever. I'm prone to kidney
infections so I experience this often. My head is clearly very warm, my brain
swells a little with the heat, and my dreams are clear and intense.

~~~
spydum
this would seem likely because you aren't sleeping well or deeply, hence able
to recall the dreams.

~~~
creep
I usually recall my dreams, fever or not. There is a marked difference between
them.

------
rayiner
> n fact, the earlier studies on R.E.M. deprivation might not have been as
> compelling as they once seemed.

> In those earlier studies, researchers kept animals from going into R.E.M.
> sleep by waking them up. “In some experiments, they wake up the animals a
> thousand times a day,” Dr. Siegel said.

So much science that I used to take for granted is garbage.

~~~
pulse7
I many cases, the science is not talking about real proofs (in the
mathematical sense) but marely about assumptions based on some (or many)
indicators. Such "science" should not be part of the real science. The real
sciense should contain ONLY the things which are proved with real proofs!

~~~
vertexFarm
If that were true we'd be paralyzed by solipsism and skepticism. Sometimes you
have to make do with a working hypothesis.

You can't eat mathematical proofs.

~~~
IncRnd
But that's the essential point, that what you call working hypothesis are
actually untested hypothesis. Using an untested hypothesis as a working
hypothesis is bad science that may actually be counterproductive, unbeknownst
to the users of the working hypothesis.

~~~
smallnamespace
You always depend on an untested hypotheses at some point. They are absolutely
unavoidable.

Here's a very simple example:

\- How much testing is sufficient? For example, as far as we can tell the laws
of physics don't vary over time scales that we can directly observe. This has
been true as far as we can tell.

\- So far so good: the hypothesis that 'the laws of physics don't change' has
been 'tested'. Next question: is that amount of testing _sufficient_?

\- Well, that seems to be an untestable proposition; it's always
philosophically possible that things get pulled out from under your feet, and
no amount of testing up to time T lets you know with complete certainty what
happens for t > T.

Go even one or two steps deeper, and you quickly find yourself resting on
either unfounded, untested, or untestable assumptions.

~~~
IncRnd
That's diverging from what was being discussed and creating a strawman that
you are now debunking. The context is the use of method-less science that uses
assumptions based upon indicators as working hypothesis - not that there are
always base assumptions but that the refutation of testing while holding
assumptions up as tested is something that is bad science.

~~~
vertexFarm
I thought what was being discussed was:

"The real sciense[sic] should contain ONLY the things which are proved with
real proofs!"

As in mathematical proofs. You can't prove most things the way you can in
mathematics, which is rock-solid through tautologies and self-consistent
abstract models. When you are observing actual reality you have to make some
assumptions.

~~~
IncRnd
What was being discussed was the reply in the context of my comment that had
been replied to. I was not the original GP poster. Sorry, if I didn't make
that clear.

------
maxander
You expect a future where brain implants will be tiny computers that make you
smarter, but perhaps instead you get a future where brain implants are tiny
heating coils that make you wake up earlier.

~~~
manmal
I‘m pretty sure I won’t have any kind of brain device installed, no matter the
upsides. No upgrades for that hardware!

~~~
Jeff_Brown
I feel the opposite. As soon as it's possible to replace biological neurons
with artificial one, even if they aren't perfect replicas, I'm in. I'm pretty
sure the mind is an emergent phenomenon robust to slight variations in the
lowest levels of hardware, and I'd like to live for billions of years. (And if
the tech lets you process faster, it could feel like trillions.)

------
Tycho
My personal theory was that dreaming allows humans to rest while staying
somewhat alert to the environment (because outside phenomena tend to manifest
inside dreams). The phased aspect of REM sleep allow groups of humans to sleep
at night while guaranteeing that some members of the group will be in REM
rather than deep sleep at any given time, so the group never becomes
completely unconscious of the surrounding environment.

~~~
bleke
My couch scientist theory is that REM sleep is phase when brains reconnects
and tunes quantum links between neuron groups (assuming brain is big quantum
computer underneath), that why there are chaotic movements.

~~~
hexane360
That's a pretty big assumption there. There's a huge difference between
"exploits a quantum effects" (like classical computers today) and "is a
quantum computer". What evidence leads you to suspect the latter?

------
pdkl95
REM cannot be strictly necessary because I don't get any REM sleep (or so
little it's difficult to detect) due to severe sleep apnea (AHI=148). Three
different sleep studies (using two unrelated labs+doctors) produced very
similar results. The hypnogram was always a narrow rectangle of rapid
oscillations (λ ~= 25-35 seconds) between NREM stages 1 and 2.

Obviously this _has_ caused harm, but it's difficult to isolate how much of
that harm (if any) is caused by lack of REM when the dips in oxygen saturation
could easily be the causing most of the problems.

------
ConcernedCoder
I think it's got more to do with maintenance, not temperature. From my own
experience, lack of sleep leads quickly to "spinning my wheels" as my thought
process becomes bogged down to the point of not being able to "finish a
thought".

At some point the brain needs to clean out molecular by-products, replenish
stores of needed neurotransmitters, I'm sure at some level there's some
garbage collection going on, maybe mark and sweep everything out of short term
memory that's been moved to long term. Maybe dreaming actively helps us to
connect disparate thoughts and concepts into some kind of of aggregate.

Some of my best thinking comes easily after a great nights sleep...

------
rubidium
Natural question follows: can humans train ourselves to do the same as animals
in water? Live a bi-phasic life where creative / analytical sides of brain
each get to "sleep"?

~~~
djsumdog
It would depend on how this evolved in the water mammals researchers have
found this in. Maybe some land mammals do the same thing, we just have
preformed this type of experiment on them yet.

If it does appear in humans, it'd probably be best to study those with extreme
insomnia or people who claim to have very short sleep patterns (<2 hours a
night) or maybe those who are narcoleptic (the other end of that scale).

~~~
darkerside
So we need a volunteer to put the electrodes on the hippopotamus?

------
candiodari
If this is true, then why are there such extreme consequences to not sleeping
for extended periods in mammals ?

Without REM sleep (deep sleep does not work by itself), you lose control of
your emotions in 2 days at most. You go insane between 1 and 2 weeks (mania,
depression, and likely quick switches between those 2), and your body will
physically shut down and die a week or so after that. (note that in humans it
hasn't been well established that death occurs, for obvious reasons. In mice,
however, it's well studied and accepted. No sleep for ~10 days, half of the
mice just die).

This seems to be a bit at odds with the idea that it's just a brain warming
technique.

[https://www.healthline.com/health/sleep-
deprivation/effects-...](https://www.healthline.com/health/sleep-
deprivation/effects-on-body#1)

[https://www.livescience.com/52592-spooky-effects-sleep-
depri...](https://www.livescience.com/52592-spooky-effects-sleep-
deprivation.html)

------
tw1010
I feel weird about this post. It feels like it's posted by people wanting to
somehow give evidence or support to the idea that sleep is good and necessary.
I feel weird about the fact that that is something that needs to be proved.
Don't you trust in the signals your body is sending you? Do you really trust a
model of average human behaviour more than your body; which is perfectly
conditioned your precise enviourment and history?

------
John_KZ
To me this looks like evidence that seals don't enjoy sleeping in water very
much. Not much else. Also sleep-deprived rats seem to consume more calories.
Wow.

------
jrmg
Have there been studies of sleep need, or sleep quality, vs temperature?

I wonder if the modern (American?) trend of running heating at night is
affecting people's sleep?

As a Briton who moved to the USA a few years ago, I found the American habit
of running heating overnight to be very odd - as I think most Europeans do. In
Britain, we tend to run heating only during the day, unless it's _extremely_
cold outside.

------
dsnuh
Do we know which animals experience the most R.E.M. sleep, or if humans
display atypical R.E.M. sleep characteristics compared to other animals?

~~~
Felz
Not a direct answer, but immediate REM sleep is a symptom of narcolepsy. So
the animal displaying the most REM sleep is probably a narcoleptic human.

It just makes you tired, no matter how much sleep you get.

------
_emacsomancer_
I thought the received wisdom was that REM sleep was connected to memory. E.g.
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768102/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768102/)

------
_bxg1
I've always found that I get exceedingly warm when I sleep. Whenever I fall
asleep on a bus or plane, I eventually wake up drenched in sweat. It's not
from bad dreams or night-terrors; my body temperature just increases. I now
wonder if it's specific to REM.

~~~
Jeff_Brown
Every night I have to throw a few blankets off of me in the early morning.

I read somewhere (?) that the body cools during sleep. Somehow one of the
implications was that taking a shower before sleep can help you sleep faster.

The fact that a body is sweating indicates not necessarily that it is hotter
than during the day; it could be that the body is trying to be cooler than it
was during the day. (Of course, if you wake up feeling hot, it's probably
because you're hot.)

Thermodynamically, it makes sense that being in a bed, with insulation against
almost all of one's body, would (once the insulation gets warm) leave someone
warmer than when they're sitting or standing -- at least if the ambient
temperature is the same in the day and night.

------
pvaldes
I would be cautious about extrapolating seal metabolism to mammal metabolism.
Diving mammals have many special adaptations to deal with high pressure,
breathing, oxygen, nitrogen etc. Is an interesting history in any case.

------
randyrand
My personal theory is that REM has many uses - one of which is giving the
brain an opportunity to do reinforcement learning.

------
prats226
Is it just heating of brain required or blood flow? One crazy way to test
would be to artificially heat the brain!

------
dghughes
If you found that interesting you should read about why our bodies are at the
temperature they are, 37C. The tl;dr is to fight off fungus.

------
textor
Just so you know, there's half a dozen of equally plausible hypotheses about
REM function, and dozens more of more fantastical. Most amusing one yet is
about synthesis of molecular chaperones that guard against aggregation of
chains produced during NREM. But honestly we just don't know.

Personally I agree with Marcus Schmidt and his idea of "energy allocation
function of sleep". Basically it says that distinct physiological states
provide viable configurations of priorities for vital functions that allow for
the lowest possible energy expenditure over the whole cycle. I.e. there's no
single specific function of REM sleep, it hosts all functions that are too
costly to prioritize during other states, and the same is true for NREM.

~~~
iagooar
That means that biology uses the same idea of having "background jobs" and
worker queues that get more relevant while the main function has a bit less to
do: many IT systems will schedule some tasks during the night when there is
not much going on, so they can prioritize them because otherwise they wouldn't
get a chance during the day.

I wonder if there are universal laws that transcend biology and technology,
all following the same rules that we haven't figured out yet.

~~~
leonroy
> many IT systems will schedule some tasks during the night when there is not
> much going on

Indeed, it’s natural that we do this but kind of funny when you consider that
our machines now have their own circadian rhythms in tune with ours.

What might our IT infrastructure look like if humans evolved to sleep far less
or not at all I wonder!

~~~
SmellyGeekBoy
> What might our IT infrastructure look like if humans evolved to sleep far
> less or not at all I wonder!

Sounds like your typical developer or sysadmin to me, so probably not much
different at all. ;)

------
albertgoeswoof
Another clickbait title, it should really be “an unproven theory for why
mammals need R.E.M. sleep based on seals”

Or even

“R.E.M. sleep might be a trait evolved to keep your brain warm at night”

