
Sleep's memory role discovered - Libertatea
http://www.bbc.com/news/health-27695144
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hyperion2010
The paper can be found at [1]. This is not a completely new finding. We have
know that motor learning induces spine formation for quite awhile. What is
novel is comparing to the sleep deprived condition and seeing effects on
structural plasticity. However, there is still a long way to go to causally
link increased spine formation to improvements on memory and motor tasks. We
like to think that spines represent a structural correlate of memory (and they
probably are), but there are a whole bunch of open questions that need to be
answered before we can actually prove that claim.

1\.
[http://www.sciencemag.org/content/344/6188/1173.full](http://www.sciencemag.org/content/344/6188/1173.full)

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robobro
Does this have to do with LTP? I feel like meditation and NMDA antagonists can
sometimes mimic the function of a good nap for me.

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hyperion2010
So LTP is generally thought to be mediated by an increase in the number of
AMPA receptors at a synapse. There have also been studies showing that the
size of spines is correlated with the number of AMPArs present at the synapse.
Whether LTP actually induces the formation of more spines is not entirely
clear. The general answer is 'we think the processes are probably related' but
it is difficult to do the experiments needed to show that the in vivo
correlates of LTP actually cause increased spine formation as part of their
downstream signaling pathways. It is worth noting that most of our knowledge
about LTP comes from studies in the hippocampus and that the relation between
spine formation and LTP may vary from brain region to brain region and even
from cell type to cell type.

tl;dr It is hypothesized that increased numbers of spines is a later stage of
the process of memory consolidation that may initially appear as LTP however
we need a whole lot more evidence to support those hypotheses.

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quotient
This seems a little sensationalist. No, the memory role of sleep was not
"discovered": a paper proposing a credible theory was published, based on
experiments performed on mice. Moreover, the proposition that is being
advanced by the paper --- that specific sleep phases strengthen particular
neural connections --- has already been made previously, and is generally
suspected to be true in academic circles anyway. So the publication of this
paper constitutes nothing more than a few (perhaps important) results
supplying a bit of further evidence in favour of an already well-supported
hypothesis; that is all.

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albertzeyer
Do you have some good reference about this hypothesis? I'm not really into
neuroscience but this really interests me. I'm more on the machine learning
side with artificial neural networks, but I often wondered whether some sleep-
like phases could get me some improvements. Of course, the question is, what
exactly should happen in that phase. What particular neural connections should
I strengthen?

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coldtea
Perhaps it has no analogous to software neural networks?

Looks like this "strengthening" is needed because there's actual "matter",
"tissue" etc involved.

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mrexroad
from what i recall (no documentation link, but it's been posted here before)
strengthening is more about making associations/connections for the things
that are important. so if you have CPU bound batch jobs that run each night
for identifying new connections between clusters of data... it seems like it'd
be pretty analogous. it's not like things we 'forgot' weren't stored, or
somehow dropped from memory; we just couldn't access it when we needed to
later, and once reminded we're fully aware.

there's also been studies on people who suffer a traumatic experience; if
they're deprived sleep following the event then the memories are less
severe/traumatic.

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asgard1024
When I studied for university exams, I used two-phase sleep cycle. I studied
from 10 AM to about 3 PM, then I had a 3-hour nap to about 6 PM, and then I
continued to study from about 7 PM to 11 PM.

I can wholeheartedly recommend it; it's quite efficient and you can easily
adapt to it from your normal single-phase cycle.

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kyberias
I'm sorry but you didn't provide enough data on your sleep. Basically you're
telling us you took a long nap in the afternoon. How much sleep did you get at
night?

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asgard1024
Well, this was like a decade and half back, so I don't have "enough data". :-)
You're right, that's what I am saying. I think I just got the amount of sleep
I needed at night (which means I woke up at around 7). This is not a technique
to reduce sleep, but to learn better.

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niels_olson
So, you slept 11 hours a day?! Wow.

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crusso
So if memories are being replayed, where are the memories coming from and to
where are they being persisted?

Is it like a backup is being formed from more short-term memory to more long-
term memory? Are long-term memories being replayed to ganglia responsible for
"muscle memory" to improve response times?

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a-priori
Recent memories (so-called 'hippocampus-dependent memories') are stored in the
hippocampus for up to about two weeks, during which time they are gradually
transferred into permanent storage in the neocortex, cerebellum, and other
parts of the brain. So, to answer your question, that is where they are
replayed from.

The hypothesis is that the hippocampus is unique in being able to store
memories quickly and after a single exposure. Most of the rest of the brain
needs time and repeated exposures to store a memory via long-term
potentiation. The role of the hippocampus is to act as a buffer where memories
are kept temporarily.

While you're sleeping, your hippocampus repeatedly activates the memory,
stimulating the brain in a similar way that the original event did. Slowly,
the neocortex begins to rewire itself through synaptic plasticity to store the
memory. After many repetitions, the memory is no longer dependent on the
hippocampus and it fades away.

I think this is the paper I'm recalling this from, but I'm not entirely sure
(this memory is several years old):

Bontempi, Bruno, et al. "Time-dependent reorganization of brain circuitry
underlying long-term memory storage." Nature 400.6745 (1999): 671-675.

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crusso
A couple of days late, but thanks for the explanation.

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andywood
I can tell you, as a person who suffered (and I mean Suffered) insomnia for 8
years, and saw countless docs.. (the cause was stress, and docs don't treat
that) .. the role for me is that it makes it work like I am a teen again. I
can memorize youtube urls now, with some practiced chunking.

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simcop2387
I had a similar discovery with sleep myself like that. I had been suffering
from un-diagnosed severe complex sleep apnea for as best as we can figure 5-10
years. once starting sleep with a BiPAP machine to help with the breathing I
went from having no REM sleep and no dreams to having them all the time. After
about the first month I could finally remember what happened the day before
clearly and without issue. The dramatic change did actually swing me a little
more towards depression for a while simply because I could finally understand
what I had been missing for so long and that there was nothing I could do to
get it back. It was definitely an interesting experience.

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DonGateley
I know that depression increases the need for sleep and napping. I also
remember reading of evidence that long term depression shrinks the
hippocampus. Could the increase in need for sleep indicate a poorly
functioning hippocampus under conditions of depression? And could such a
connection, if it exists, be an avenue for finding better chemical (or
electrical) treatment for depression?

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bernardlunn
I was going to comment but decided that a nap was more important

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Digit-Al
And yet you still commented. The nap can't have been that important after all
;-)

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osiris679
Unless it was a sleep-induced comment. Their memory was just an empty text box
waiting to be filled.

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BrandonMarc
Or perhaps the post came during the nap!

[http://xkcd.com/269/](http://xkcd.com/269/)

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leishulang
great excuse to bring sleep bag to work.

