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  • It's 4 a.m., and the big test is in 8 hours, followed by a piano recital.

  • You've been studying and playing for days, but you still don't feel ready for either.

  • So, what can you do?

  • Well, you can drink another cup of coffee and spend the next few hours cramming and practicing, but believe it or not,

  • you might be better off closing the books, putting away the music, and going to sleep.

  • Sleep occupies nearly a third of our lives, but many of us give surprisingly little attention and care to it.

  • This neglect is often the result of a major misunderstanding.

  • Sleep isn't lost time, or just a way to rest when all our important work is done.

  • Instead, it's a critical function, during which your body balances and regulates its vital systems,

  • effecting respiration and regulating everything from circulation to growth and immune response.

  • That's great, but you can worry about all those things after this test, right?

  • Well, not so fast.

  • It turns out that sleep is also crucial for your brain, with a fifth of your body's circulatory blood being channeled to it as you drift off.

  • And what goes on in your brain while you sleep is an intensely active period of restructuring that's crucial for how our memory works.

  • At first glance, our ability to remember things doesn't seem very impressive at all.

  • 19th-century psychologist Hermann Ebbinghaus demonstrated that we normally forget 40% of new material within the first 20 minutes, a phenomenon known as the forgetting curve.

  • But this loss can be prevented through memory consolidation, the process by which information is moved from our fleeting short-term memory to our more durable long-term memory.

  • This consolidation occurs with the help of a major part of the brain known as the hippocampus.

  • Its role in long-term memory formation was demonstrated in the 1950s by Brenda Milner in her research with a patient known as H.M.

  • After having his hippocampus removed, H.M.'s ability to form new short-term memories was damaged, but he was able to learn physical tasks through repetition.

  • Due to the removal of his hippocampus, H.M.'s ability to form long-term memories was also damaged.

  • What this case revealed, among other things, was that the hippocampus was specifically involved in the consolidation of long-term declarative memory,

  • such as the facts and concepts you need to remember for that test, rather than procedural memory, such as the finger movements you need to master for that recital.

  • Milner's findings, along with work by Eric Kandel in the 90's, have given us our current model of how this consolidation process works.

  • Sensory data is initially transcribed and temporarily recorded in the neurons as short-term memory.

  • From there, it travels to the hippocampus, which strengthens and enhances the neurons in that cortical area.

  • Thanks to the phenomenon of neuroplasticity, new synaptic buds are formed, allowing new connections between neurons, and strengthening the neural network where the information will be returned as long-term memory.

  • So why do we remember some things and not others?

  • Well, there are a few ways to influence the extent and effectiveness of memory retention.

  • For example, memories that are formed in times of heightened feeling, or even stress, will be better recorded due to the hippocampus's link with emotion.

  • But one of the major factors contributing to memory consolidation is... you guessed it, a good night's sleep.

  • Sleep is composed of four stages, the deepest of which are known as slow-wave sleep and rapid eye movement.

  • EEG machines monitoring people during these stages have shown electrical impulses moving between the brainstem, hippocampus, thalamus, and cortex, which serve as relay stations of memory formation.

  • And the different stages of sleep have been shown to help consolidate different types of memories.

  • During the non-REM slow-wave sleep, declarative memory is encoded into a temporary store in the anterior part of the hippocampus.

  • Through a continuing dialogue between the cortex and hippocampus, it is then repeatedly reactivated, driving its gradual redistribution to long-term storage in the cortex.

  • REM sleep, on the other hand, with its similarity to waking brain activity, is associated with the consolidation of procedural memory.

  • So based on the studies, going to sleep three hours after memorizing your formulas and one hour after practicing your scales would be the most ideal.

  • So hopefully you can see now that skimping on sleep not only harms your long-term health, but actually makes it less likely that you'll retain all that knowledge and practice from the previous night,

  • all of which just goes to affirm the wisdom of the phrase, "Sleep on it."

  • When you think about all the internal restructuring and forming of new connections that occurs while you slumber,

  • you could even say that proper sleep will have you waking up every morning with a new and improved brain, ready to face the challenges ahead.

It's 4 a.m., and the big test is in 8 hours, followed by a piano recital.

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B1 US TED-Ed hippocampus sleep memory consolidation term

【TED-Ed】The benefits of a good night's sleep - Shai Marcu

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    稲葉白兎 posted on 2015/11/17
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