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← How sound can hack your memory while you sleep

Can you cram for a test while you sleep? Our intrepid neuroscientists attempt to enhance memory by running experiments on subjects while they sleep. You'll be surprised by the results.

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Showing Revision 3 created 06/11/2018 by Brian Greene.

  1. Greg Gage: Who wouldn't love
    acing a geography exam,
  2. remembering all the locations
    of the countries on a map
  3. or avoiding embarrassing situations
    of suddenly forgetting the person's name
  4. standing right in front of you.
  5. It turns out that memory,
    like other muscles in the body,
  6. can be strengthened and enhanced.
  7. But instead of practicing
    with flash cards,
  8. there may be an interesting way
  9. that we can hack our memory
    while we sleep.
  10. (Music)

  11. Why do we sleep?

  12. This has been a question asked
    since the early days of civilization.
  13. And while we may not know
    the exact answer,
  14. there are a number of really
    good theories about why we need it.
  15. Sleep is when the brain transfers
    short-term memories
  16. experienced throughout the day
  17. into long-term memories.
  18. This process is called
    memory consolidation,
  19. and it's the memory consolidation theory
    that has scientists wondering
  20. if we can enhance
    certain memories over others.
  21. There was a paper recently
    in the journal "Science"
  22. by Ken Paller and his colleagues
    at Northwestern
  23. that seemed to show that this may be true,
  24. and that piqued our curiosity.
  25. Joud has been working
    on a DIY version of this task
  26. to see if we can improve memories
    through the use of sound in sleep.
  27. So Joud, how do you test if we can
    improve our memories with sleep?
  28. Joud Mar’i: We need a human subject.

  29. [Step 1: Play a game]

  30. We have a memory game
    that we have on an iPad,
  31. and then we make our subject
    play this game
  32. and remember the images
    and where they appear on the screen.
  33. GG: So this is like a memory game
    you used to play as a child,

  34. which picture was where.
  35. And we tie each picture
    with a sound that represents it.
  36. JM: So, if you can see
    a picture of a car, for example,

  37. and you would hear the car engine.
  38. (Car engine starting)

  39. GG: Just before you go to sleep
    we're going to test you.

  40. We're going to see how well
    you remember where the pictures are.
  41. Every time you see the picture,
    you're going to hear the sound.
  42. And now comes the experiment.
  43. You're going to go take a nap.
  44. [Step 2: Take a nap]
  45. And while you're sleeping,
    we're going to be recording your EEG.
  46. JM: And then we wait for them to go
    into what's called the slow-wave sleep,

  47. which is the deepest phase of your sleep
    where it's really hard for you to wake up.
  48. GG: OK, pause.

  49. So, here's some information on sleep.
  50. There are four stages:
    we have lighter stages of sleep and REM,
  51. but what we're interested in
    is called slow-wave sleep.
  52. And it gets its name
    from the electrical signals
  53. called Delta waves
    that we record from the brain.
  54. This is the part of sleep
    where scientists believe
  55. that memory consolidation can happen.
  56. In this deep period of sleep,
  57. we're going to do something
    that you don't know we're going to do.
  58. JM: Here's where the tricky part comes,
    and we start playing our cues.

  59. (Car engine starting)

  60. GG: Do you play all the cues?

  61. JM: No. We only want to play half of them
    to see if there's a difference.

  62. GG: So your hypothesis is

  63. the one that they were listening to
    while they're sleeping
  64. they're going to do better at.
  65. JM: Yes, exactly.

  66. GG: When you wake back up
    and play the game again,

  67. do you do better or worse
    than before a nap?
  68. What we found is that if we played you
    a cue during your sleep,
  69. for example, a car --
  70. You would remember
    the position of that car
  71. when you woke back up again.
  72. But if we didn't play you the cue
    during the sleep,
  73. for example, a guitar,
  74. you'd be less likely to remember
    that guitar when you woke up.
  75. The memories that were cued
    they remembered better
  76. than the ones they weren't,
  77. even though they don't remember
    hearing those sounds?
  78. JM: Yes, we ask them.

  79. GG: We know they're sleeping,
    they can't hear it, they wake up,

  80. they do better on those
    than the ones you didn't play.
  81. GG: That's amazing.
    JM: It's like magic.

  82. GG: Joud ran this experiment on 12 people
    and the results were significant.

  83. It's not that you remember things better;
    it's that you forget them less.
  84. I was a huge skeptic when I first heard
    that you could do better at a memory test
  85. just by playing sounds during sleep.
  86. But we replicated these experiments.
  87. The facts and memories we collect
    throughout the day are very fragile,
  88. and they are easily lost and forgotten.
  89. But by reactivating them during sleep,
    even without us being aware,
  90. it seems like we could make them
    more stable and less prone to forgetting.
  91. That's pretty incredible.
  92. Our brains are still active
    even when we're not.
  93. So if you're like me and a bit forgetful,
  94. perhaps a solution is a pair
    of headphones and a soft couch.