

Direct Evidence Of Role Of Sleep In Memory Formation Is Uncovered - codeodor
http://www.sciencedaily.com/releases/2009/09/090915174506.htm

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mgreenbe
Original article:
[http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.238...](http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.2384.html)

I was inclined to be skeptical---breaking news, shocking the brain during
sleep impairs performance---but they used three different groups of rats:

    
    
      ...we tested the role of SPW-Rs on memory consolidation.
      Three groups of rats (test group, n = 7; stimulated 
      controls, n = 7; unimplanted controls, n = 12) were 
      trained to find food rewards ... . 
    
      During post-training rest and sleep, all of the online-
      detected ripples were suppressed by commissural 
      stimulations in test rats (average online detection rate 
      was 86.0 ± 1.3% (s.e.m.) of post hoc detected SPW-Rs;
      ...). Stimulated control rats underwent the same 
      protocol, except that a random delay (80–120 ms)
      was introduced between SPW-R detection and stimulation, 
      ensuring that the stimulations occurred mainly outside of 
      the ripple episodes.
    

Now check this out:

    
    
      Thus, these control rats received the same number of 
      stimulations as test rats, but their hippocampal
      ripples were left largely intact. The global architecture 
      of sleep and the local field potential power in distinct 
      sleep stages were not modified by the suppression of 
      SPW-Rs ... .  As stimulation outside SPW-Rs had
      no detectable effect on task performance ..., the two 
      control groups were pooled and compared with test rats. 
      Performance of the test rats was significantly impaired 
      ... .
    

Cool experiment design with an intriguing result.

~~~
codeodor
Thanks for that. I was going to include the link to that, but when I clicked
for the full text it asked me to subscribe.

Now that I've gone back, I was able to grab the PDF.

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a-priori
In doing research for another comment I posted here, I came across an article
that does a very good job of summarizing the current state of research into
the role of sleep in memory consolidation.

[http://www.nature.com/nature/journal/v437/n7063/abs/nature04...](http://www.nature.com/nature/journal/v437/n7063/abs/nature04286.html)

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jasongullickson
_"Sharp wave ripples are intense, compressed oscillations that occur in the
hippocampus when the hippocampus is working off-line, most often during stage
four sleep, which, along with stage three, is the deepest level of sleep."_

I'm not an expert on the subject, but how can two stages both be the
"deepest"?

~~~
Leon
Both stages have delta waves in the same range but induce different effects on
the brain. They're both characterized by the same measure for depth (of
sleep).

To clarify with more, specific information:
<http://en.wikipedia.org/wiki/Slow-wave_sleep>

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dzlobin
"Sharp wave ripples are intense, compressed oscillations that occur in the
hippocampus when the hippocampus is working “off-line,” most often during
stage four sleep, which, along with stage three, is the deepest level of
sleep."

So do people who practice polyphasic sleep have awful memory?

~~~
skolor
The way I understand it, Polyphasic sleep is designed to trick your body into
skipping the first two stages of sleep, so you spend all the time in the last
two, where the biggest benefits are.

~~~
dzlobin
That seems a bit off, trick your body into skipping the first two stages
by...staying awake?

~~~
dkersten
Not quite, you try and sleep at set times and after some time you adjust to
actually sleep during those times. Since the sleep period is typically very
short (~30 minutes), the idea is that your body adjusts. From what I've read,
people who've tried it (for longer than a month or two, ie they actually
adjusted properly) found they were just as rested as everyone else.

Having said that, who knows what negative effects it may have on them...

~~~
scott_s
I've read multiple accounts of people who _tried_ it and _claimed_ they were
just as rested. But I emphasize try because they no longer do it, and I bet
the reason is they were not just as rested.

edit: polyphasic sleep discussion:
<http://news.ycombinator.com/item?id=652650>

~~~
dzlobin
<http://www.supermemo.com/help/faq/polyphasic.htm> This was a great find,
thanks for the link. Pretty much proved all my thoughts true

~~~
dkersten
Interesting read.

There was that guy (though I cannot remember who it was) who claimed to have
sustained polyphasic sleep for 9 months and only stopped it because he found
it hard to interact with people and socialise because his schedule was too
different from everyone elses. But, I have no evidence, so.. that FAQ seems
reasonable though.

~~~
apr
Steve Pavlina?

[http://www.stevepavlina.com/blog/2007/03/polyphasic-sleep-
on...](http://www.stevepavlina.com/blog/2007/03/polyphasic-sleep-one-year-
later/)

he has a ton of articles on his blog describing his experience

~~~
dkersten
Yeah, that was probably who I was thinking of. Thanks for the link.

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johnohara
_Those rats that selectively had all ripple events eliminated by electrical
stimulation were impeded in their ability to learn from the training, as
compressed information was unable to leave the hippocampus and transfer to the
neocortex._

Probably remembered being electrically stimulated instead.

~~~
bdr
I think the experiment design eliminates that possibility. Why would this
group of rats do worse than the ones that were electrically stimulated, but
not in a way that disrupted the ripple events?

