6 ms·

Direct Evidence Of Role Of Sleep In Memory Formation Is Uncovered

76 points by codeodor 17y ago

mgreenbe 17y ago
Original article: http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.2384.html http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.238... 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 17y ago
  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.
jasongullickson 17y ago
"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 17y ago
  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 http://en.wikipedia.org/wiki/Slow-wave_sleep
dzlobin 17y ago
"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 17y ago
  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.
  - absconditus 17y ago
    Is there any proof of this or is this just what polyphasic sleepers tell themselves?
    - skolor 17y ago
      You're right, I can't find any evidence other than several polyphasic sleepers' blogs. I can find a handful of articles on polyphasic sleep, but all of them are behind pay-walls and I can't get to any actual data. The only actual data I could find related to sleep periods evening out to a similar daily distribution after 45 days.
      - thirdusername 17y ago
        I could probobly help you access the journals if you want to investigate further, I'd be interested in hearing the answer.
        skolor 17y ago
        At this point, I don't think there is much in the way of real work behind it. From what I can tell there has been one paper written about it (http://www.informaworld.com/smpp/ftinterface?content=a782431473&rt=0&format=pdf http://www.informaworld.com/smpp/ftinterface?content=a782431...), which is a "field study", not a laboratory test. All I seem to find are pseudo-science and anecdotes supporting both sides of the argument, with no actual evidence.
deleted 17y ago
[deleted]
johnohara 17y ago
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 17y ago
  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?
a-priori 17y ago
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/nature04286.html http://www.nature.com/nature/journal/v437/n7063/abs/nature04...

76 points by codeodor 17y ago

Original article: http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.2384.html http://www.nature.com/neuro/journal/vaop/ncurrent/abs/nn.238... 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 17y ago
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.

jasongullickson 17y ago

"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 17y ago
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 http://en.wikipedia.org/wiki/Slow-wave_sleep

dzlobin 17y ago

"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 17y ago
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.
- absconditus 17y ago
  Is there any proof of this or is this just what polyphasic sleepers tell themselves?
  - skolor 17y ago
    You're right, I can't find any evidence other than several polyphasic sleepers' blogs. I can find a handful of articles on polyphasic sleep, but all of them are behind pay-walls and I can't get to any actual data. The only actual data I could find related to sleep periods evening out to a similar daily distribution after 45 days.
    - thirdusername 17y ago
      I could probobly help you access the journals if you want to investigate further, I'd be interested in hearing the answer.
      - skolor 17y ago
        At this point, I don't think there is much in the way of real work behind it. From what I can tell there has been one paper written about it (http://www.informaworld.com/smpp/ftinterface?content=a782431473&rt=0&format=pdf http://www.informaworld.com/smpp/ftinterface?content=a782431...), which is a "field study", not a laboratory test. All I seem to find are pseudo-science and anecdotes supporting both sides of the argument, with no actual evidence.

deleted 17y ago

[deleted]

johnohara 17y ago

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 17y ago
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?

a-priori 17y ago

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/nature04286.html http://www.nature.com/nature/journal/v437/n7063/abs/nature04...