The benefits of a good night's sleep - Shai Marcu

6,721,444 views ・ 2015-01-05

TED-Ed


Please double-click on the English subtitles below to play the video.

00:07
It's 4 a.m., and the big test is in eight hours,
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followed by a piano recital.
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You've been studying and playing for days, but you still don't feel ready for either.
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So, what can you do?
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Well, you can drink another cup of coffee
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and spend the next few hours cramming and practicing,
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but believe it or not,
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you might be better off closing the books, putting away the music,
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and going to sleep.
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Sleep occupies nearly a third of our lives,
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but many of us give surprisingly little attention and care to it.
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This neglect is often the result of a major misunderstanding.
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Sleep isn't lost time,
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or just a way to rest when all our important work is done.
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Instead, it's a critical function,
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during which your body balances and regulates its vital systems,
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affecting respiration
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and regulating everything from circulation to growth and immune response.
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That's great, but you can worry about all those things after this test, right?
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Well, not so fast.
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It turns out that sleep is also crucial for your brain,
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with a fifth of your body's circulatory blood
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being channeled to it as you drift off.
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And what goes on in your brain while you sleep
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is an intensely active period of restructuring
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that's crucial for how our memory works.
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At first glance,
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our ability to remember things doesn't seem very impressive at all.
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19th century psychologist Herman Ebbinghaus
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demonstrated that we normally forget 40% of new material
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within the first twenty minutes,
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a phenomenon known as the forgetting curve.
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But this loss can be prevented through memory consolidation,
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the process by which information is moved
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from our fleeting short-term memory to our more durable long-term memory.
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This consolidation occurs with the help of a major part of the brain,
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known as the hippocampus.
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Its role in long-term memory formation
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was demonstrated in the 1950s by Brenda Milner
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in her research with a patient known as H.M.
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After having his hippocampus removed,
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H.M.'s ability to form new short-term memories was damaged,
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but he was able to learn physical tasks through repetition.
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Due to the removal of his hippocampus,
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H.M.'s ability to form long-term memories was also damaged.
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What this case revealed, among other things,
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was that the hippocampus was specifically involved
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in the consolidation of long-term declarative memory,
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such as the facts and concepts you need to remember for that test,
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rather than procedural memory,
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such as the finger movements you need to master for that recital.
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Milner's findings, along with work by Eric Kandel in the 90's,
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have given us our current model of how this consolidation process works.
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Sensory data is initially transcribed
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and temporarily recorded in the neurons as short-term memory.
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From there, it travels to the hippocampus,
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which strengthens and enhances the neurons in that cortical area.
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Thanks to the phenomenon of neuroplasticity,
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new synaptic buds are formed, allowing new connections between neurons,
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and strengthening the neural network
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where the information will be returned as long-term memory.
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So why do we remember some things and not others?
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Well, there are a few ways to influence
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the extent and effectiveness of memory retention.
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For example, memories that are formed in times of heightened feeling,
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or even stress,
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will be better recorded due to the hippocampus' link with emotion.
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But one of the major factors contributing to memory consolidation is,
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you guessed it,
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a good night's sleep.
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Sleep is composed of four stages,
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the deepest of which are known as slow-wave sleep
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and rapid eye movement.
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EEG machines monitoring people during these stages
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have shown electrical impulses
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moving between the brainstem, hippocampus, thalamus, and cortex,
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which serve as relay stations of memory formation.
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And the different stages of sleep have been shown to help consolidate
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different types of memories.
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During the non-REM slow-wave sleep,
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declarative memory is encoded into a temporary store
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in the anterior part of the hippocampus.
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Through a continuing dialogue between the cortex and hippocampus,
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it is then repeatedly reactivated,
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driving its gradual redistribution to long-term storage in the cortex.
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REM sleep, on the other hand, with its similarity to waking brain activity,
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is associated with the consolidation of procedural memory.
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So based on the studies,
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going to sleep three hours after memorizing your formulas
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and one hour after practicing your scales would be the most ideal.
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So hopefully you can see now that skimping on sleep
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not only harms your long-term health,
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but actually makes it less likely
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that you'll retain all that knowledge and practice from the previous night,
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all of which just goes to affirm the wisdom of the phrase, "Sleep on it."
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When you think about all the internal restructuring
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and forming of new connections that occurs while you slumber,
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you could even say that proper sleep
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will have you waking up every morning with a new and improved brain,
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ready to face the challenges ahead.
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