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Sleep keeps important memories safe
February 1st, 2011
05:00 PM ET

Sleep keeps important memories safe

Here's another reason to get some good sleep in the week leading up to a major test or presentation: Sleep selectively enhances memories that you expect to need in the future, a new study suggests.

Researchers in Germany tested a group of 141 healthy adult participants on tasks involving recalling words, locating a two-dimensional object, and reproducing a sequence of finger taps. Their results are published in the Journal of Neuroscience.

They found that participants who knew they would be tested on these things later remembered them better than those who didn't know after a good night's sleep of about 7 to 8 hours. Participants who were not permitted to sleep did not show memory improvement, regardless of whether or not they thought there would be a test.

This research sheds light on the intricacies of how memory works while we sleep, said Michael Breus, sleep expert in Scottsdale, Arizona, and author of "Beauty Sleep." Breus, who was not involved in the study, praised the experimental design and noted that it looked at the effects of both declarative memory (recalling facts and events) and procedural memory (skill sets).

Some next steps would be to figure out exactly how long these memories last, and how accurate they are later, Breus said. The longer you have a memory, the less accurate it usually becomes. But if there is a lot of emotion attached to an event, it stays clearer longer. For instance, you probably remember the moment when you learned of the attacks on September 11, 2001, but maybe not what was happening when you ordered a pizza last month.

How it works

Memory first gets encoded while you're awake through a horseshoe-shaped brain region called the hippocampus, where it gets temporarily stored for up to about a day or two, said Jan Born, study co-author and researcher at the University of Lübeck in Germany. But you may forget that memory relatively quickly because you get exposed to other things that are similar to the original memory, and the new information tends to override old information.

During sleep, memories get consolidated and stored for the longer haul in the neocortex. Longterm memory storage can last from a day or to up to a lifetime.

That transfer of memories from short to long-term storage takes place during slow-wave sleep, a stage of deep sleep that cycles with rapid eye movement (REM). During this slow-wave sleep, there is no dreaming, and if you wake up during it, you feel especially groggy. A typical night's sleep begins with non-REM sleep - light followed by deep sleep - followed by an REM stage, and then the two cycle with each other.

There is, however, some controversy about the role of REM sleep in memory. Traditionally the view has been that slow-wave sleep is physically restorative - in other words, tissue repair and metabolism and weight changes occur during this phase of snoozing - and that REM sleep is physically restorative, Breus said. But so much happens during sleep that it's hard to pin down exactly which phase is responsible for what.

"This study does bring to light some new possibilities in that area," he said.

Even a nap helps

Many other studies have found that even a nap benefits the consolidation of memory. Interestingly, a 2010 study in Current Biology found that naps boost memory only if you dream, even though memory enhancement appears to occur during slow-wave, non-dreaming sleep stages.

But in preparation for a big exam, a single night of good sleep doesn't help as much as a week or so consistently, Born said.


soundoff (32 Responses)
  1. Alethea

    Hooah

    February 1, 2011 at 18:53 | Report abuse | Reply
    • duh

      another failed test "Participants who were not permitted to sleep"
      Now how about testing people that sleep 5hours a night as the status quo, not taking people used to sleeping 9+ hours and no letting them sleep. otherwise these test results just prove people used to sleeping a long time are groggy int he morning and all day which is already a known fact. stop wasting money on this crap. use it for HIV and aids research

      February 2, 2011 at 01:07 | Report abuse |
    • Bry

      Read it carefully, Duh, another experimental group was allowed to have the same amount of sleep, they just weren't aware they would be tested the next day. They are saying that sleep improves memories that you think you may have to use in the future. As dumb as some studies are, if its being published in J of Neuroscience then it must be pretty legit.

      February 2, 2011 at 10:32 | Report abuse |
    • Rones

      Why do people always assume that this research money would otherwise go towards AIDS or cancer research? We spend literally billions of dollars on those diseases, they aren't exactly wanting for money. This study probably cost a university a couple thousand dollars. You also have to keep in mind that this type of research can have far-reaching effects that aren't immediately obvious. Will it benefit Alzheimer's research? Will someone use this to develop a therapy for traumatic brain injury? We really have no idea, but learning more about the human brain and its natural processes is never a waste of money.

      February 2, 2011 at 12:34 | Report abuse |
  2. JoeGrammar

    It'd be interesting to see the results when mixed with Alcohol abuse.

    February 1, 2011 at 19:10 | Report abuse | Reply
    • MC

      Yeah. That and alcohol abuse too.

      February 2, 2011 at 00:04 | Report abuse |
  3. billy

    I sleep a whole bunch, but I cannot remember anything. Where am I?

    February 1, 2011 at 19:48 | Report abuse | Reply
    • D

      Ward C

      February 1, 2011 at 19:52 | Report abuse |
    • Eric P

      You probably have sleep apnea, and arent getting a good nights sleep. 1 in 5 americans has it, and many dont know.

      February 1, 2011 at 20:38 | Report abuse |
    • duh

      the test was not a test of people who sleep long to ones who dont. it was a test of people who sleep and ones not allowed to sleep. so if we didnt let u sleep u would remember less and therefore when u sleep u would be smarter even though u are not.

      February 2, 2011 at 01:08 | Report abuse |
    • billy

      Have someone do their job without any sleep vs someone who gets sleep. I wonder who would perform better.

      February 2, 2011 at 02:17 | Report abuse |
  4. JoMamma

    Now thats funny D

    February 1, 2011 at 20:11 | Report abuse | Reply
  5. Peter

    An encounter of your mother in law naked is not something you would want to keep in your memory. First hand experience.

    Whats been seen, cannot be unseen.

    February 1, 2011 at 20:54 | Report abuse | Reply
    • Yesbutno

      Nice, i needed that.

      February 1, 2011 at 23:12 | Report abuse |
    • MC

      Depends on the mother in law. Mine's a MILILF.

      February 2, 2011 at 00:05 | Report abuse |
    • Pink Dolphins are Beautiful

      Some societies and cultures are more comfortable with nudity of people of all ages than American culture. No matter people look like they deserve respect.

      February 2, 2011 at 05:36 | Report abuse |
    • Ercan

      Carolyn – Awesome job Phil! They're all amazing, but I epcasielly love the one on the bridge, but you know I have a thing for covered bridges! Where's this park?

      April 14, 2012 at 15:46 | Report abuse |
  6. NobodySpecial

    Reminds me of the ending song to the Dawson's Creek episode "The All Nighter" called "Who Needs Sleep?" by the Bare Naked Ladies.

    This is the chorus . . .
    "Who needs sleep?
    well you're never gonna get it
    Who needs sleep?
    tell me what's that for
    Who needs sleep?
    be happy with what you're getting
    There's a guy who's been awake
    since the Second World War"

    February 1, 2011 at 21:02 | Report abuse | Reply
  7. Dufus Wainwright

    Perhaps those people who knew they were going to be tested on it later simply worked harder to learn/internalize while they were reviewing the material originally, and it wasn't the sleep at all. I'd be interested to see the details of the experiment.

    February 1, 2011 at 21:26 | Report abuse | Reply
    • mm

      "Participants who were not permitted to sleep did not show memory improvement, regardless of whether or not they thought there would be a test."

      February 1, 2011 at 23:52 | Report abuse |
  8. Mike from NYC since 1955

    I have been in noise ridden mid town NYC so long I can't sleep unless
    I am in a real loud noisy environment wherever I travel ,maybe that is why I
    have so many vivid dreams of nasty people returning from
    my past life. I wake up and find that they are gone sweet dreams indeed.

    February 1, 2011 at 22:29 | Report abuse | Reply
  9. Yesbutno

    Sometimes when i dream of Jenie, when i wake up my arm is tired and my shpeener is all beat up.

    February 1, 2011 at 23:15 | Report abuse | Reply
  10. Dr Bill Toth

    Important research and a big question...how did they determine it was the sleep that made the difference vs the participants simply knowing they were going to be tested.? Live with Intention, DrBillToth.com/blog

    February 1, 2011 at 23:50 | Report abuse | Reply
  11. Vashish

    Great for your exam

    February 2, 2011 at 00:56 | Report abuse | Reply
  12. Owlbrain

    I was going to post, but forgot what I was going to say-I'll be back
    after sleeping on it.

    February 2, 2011 at 01:05 | Report abuse | Reply
  13. mmi16

    zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

    February 2, 2011 at 04:51 | Report abuse | Reply
  14. SleepDeprived

    What a hot chick!

    February 2, 2011 at 05:11 | Report abuse | Reply
  15. old news

    this is not news. they've been teaching the phenomenon of memory reinforcement and consolidation during sleep in college physiology for years. like, there are old ass text books with this information in it. im a graduate student and ive heard it in at least 3 courses without even trying.

    February 2, 2011 at 10:53 | Report abuse | Reply
    • Rones

      For a graduate student, you don't read well. Yes, we consolidate memories when we sleep. The point of this study was that we consolidate memories that we think are important better than we do memories than seem unimportant.

      February 2, 2011 at 12:39 | Report abuse |
  16. Sleepless in Seattle

    I appreciate Rones comment on February 2nd at 12:34 when he wrote about the potential value of this sort of research. Many important lessons emerge from topics that may not be recognized as the "big topics" such as cancer, HIV or cardiology. I especially agree with the point that research on sleeping may lend great insights on the recovery of various types of brain injuries and the power of neuroplasticity.

    February 5, 2011 at 01:19 | Report abuse | Reply
  17. Ivonne

    I'm enjoyed this article very much. While in college and taking a Neuroscience class I did a research paper on "Sleep Deprivation and Memory" and as it mentions here, sleep is very important to obtain long term memory. Sleep has different faces which are divided into Non-rapid eye movement (NREM) and Rapid eye movement (REM). which influence how well you sleep and also the intensity with which you remember.

    February 13, 2011 at 09:10 | Report abuse | Reply
  18. Marcelino

    – Awesome job Phil. I especially love the first one where Craig is hlinodg Jessica and they are looking deep in each others eyes.You take pictures as well as you play. Very talented.

    April 8, 2012 at 11:59 | Report abuse | Reply

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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.