A walk through the stages of sleep
-
0:00 - 0:03Sleep is perhaps the
single most effective thing -
0:03 - 0:05that we can do each and every day
-
0:05 - 0:09to reset the health
of our brain and our body. -
0:09 - 0:13And by understanding a little bit more
about what sleep is, -
0:13 - 0:17perhaps we can get the chance to improve
both the quantity and the quality -
0:17 - 0:18of our sleep.
-
0:18 - 0:20[Sleeping with Science]
-
0:20 - 0:22(Music)
-
0:23 - 0:26So, exactly what is sleep?
-
0:26 - 0:29Well, sleep, at least in human beings,
-
0:29 - 0:32is subdivided into two main types.
-
0:32 - 0:35On the one hand, we have
non-rapid eye movement sleep, -
0:35 - 0:37or non-REM sleep for short.
-
0:37 - 0:38But on the other hand,
-
0:38 - 0:42we have rapid eye movement
sleep, or REM sleep. -
0:42 - 0:46And non-REM sleep has been
further subdivided -
0:46 - 0:48into four separate stages,
-
0:48 - 0:52unimaginatively called
stages one through four, -
0:52 - 0:54increasing in their depth of sleep.
-
0:54 - 0:58And as we go into those light stages
of non-REM sleep, -
0:58 - 1:01your heart rate starts to decrease,
-
1:01 - 1:03your body temperature starts to drop
-
1:03 - 1:07and your electrical brain wave activity
starts to slow down. -
1:07 - 1:11But as we move into deeper
non-rapid eye movement sleep, -
1:11 - 1:13stages three and four,
-
1:13 - 1:16now all of a sudden the brain erupts
-
1:16 - 1:20with these huge, big,
powerful brain waves. -
1:20 - 1:25The body is actually recharged
in terms of its immune system. -
1:25 - 1:30We also get this beautiful overhaul
of our cardiovascular system. -
1:30 - 1:33And, in fact, upstairs in the brain,
-
1:33 - 1:36deep non-REM sleep
will help consolidate memories -
1:36 - 1:40and fixate them into the neural
architecture of the brain. -
1:40 - 1:42So that's non-REM sleep.
-
1:42 - 1:45But let's come on to REM sleep,
-
1:45 - 1:47which is the other main type of sleep.
-
1:47 - 1:51And it's during REM sleep
when we principally have the most vivid, -
1:51 - 1:54the most hallucinogenic types of dreams.
-
1:54 - 1:58The brain wave activity
actually starts to speed up again. -
1:58 - 2:05It's during REM sleep that we receive
almost a form of emotional first aid. -
2:05 - 2:09And it's also during REM sleep
where we get a boost for creativity, -
2:09 - 2:12that it stitches information together
-
2:12 - 2:15so that we wake up with solutions
-
2:15 - 2:18to previously difficult problems
that we were facing. -
2:18 - 2:21Coming back to these two types of sleep,
-
2:21 - 2:25it turns out that non-REM
and REM will play out -
2:25 - 2:29in a battle for brain domination
throughout the night, -
2:29 - 2:33and that cerebral war
is going to be won and lost -
2:33 - 2:35every 90 minutes,
-
2:35 - 2:38and then it's going to be
replayed every 90 minutes. -
2:39 - 2:44And what this produces is a standard
cycling architecture of human sleep, -
2:44 - 2:46a standard 90-minute cycle.
-
2:47 - 2:48But what's different, however,
-
2:49 - 2:54is that the ratio of non-REM to REM
within those 90-minute cycles -
2:54 - 2:57changes as we move across the night,
-
2:57 - 3:00such that in the first half the night,
-
3:00 - 3:03the majority of those 90-minute cycles
-
3:03 - 3:06are comprised of lots
of deep non-REM sleep, -
3:06 - 3:10particularly stages three and four
of non-REM sleep. -
3:10 - 3:13But as we push through
to the second half of the night, -
3:13 - 3:17now that seesaw balance
actually shifts over, -
3:18 - 3:21and instead, most of those
90-minute cycles -
3:21 - 3:26are comprised of a lot more
rapid eye movement sleep, or dream sleep, -
3:26 - 3:29as well as stage-two non-REM sleep,
-
3:29 - 3:31that lighter form of non-REM sleep.
-
3:31 - 3:34And it turns out
that there are implications -
3:34 - 3:38for understanding how sleep
is structured in this way. -
3:38 - 3:43Let's take someone who typically
goes to bed at 10pm, -
3:43 - 3:45and they wake up at 6am,
-
3:45 - 3:47so they have an eight-hour sleep window.
-
3:47 - 3:50But this morning,
they have to wake up early -
3:50 - 3:52for an early morning meeting,
-
3:52 - 3:54or they want to get
a jump start on the day -
3:54 - 3:56to get to the gym.
-
3:56 - 4:00And as a consequence, they have to wake up
at 4am in the morning, -
4:00 - 4:02rather than 6am in the morning.
-
4:02 - 4:04How much sleep have they actually lost?
-
4:04 - 4:07Two hours out of
an eight-hour night of sleep -
4:07 - 4:11means that they've lost
25 percent of their sleep. -
4:12 - 4:14Well, yes and no.
-
4:14 - 4:17They have lost 25 percent
of all of their sleep, -
4:17 - 4:22but because REM sleep comes
mostly in the second half of the night -
4:22 - 4:24and particularly in those last few hours,
-
4:24 - 4:29they may have lost perhaps
50, 60, maybe even 70 percent -
4:29 - 4:31of all of their REM sleep.
-
4:31 - 4:36So there are real consequences
to understanding what sleep is -
4:36 - 4:38and how sleep is structured.
-
4:38 - 4:42And we'll learn all about the benefits
of these different stages of sleep -
4:42 - 4:46and the detriments that happen
when we don't get enough of them -
4:46 - 4:47in subsequent episodes.
- Title:
- A walk through the stages of sleep
- Speaker:
- Matt Walker
- Description:
-
Did you know you go on a journey every night after you close your eyes? Sleep scientist Matt Walker breaks down the difference between REM (Rapid-Eye Movement) and non-REM sleep, what occurs during each stage of sleep -- and why it's important to get enough of both.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED Series
- Duration:
- 04:47
Erin Gregory edited English subtitles for A walk through the stages of sleep | ||
Erin Gregory approved English subtitles for A walk through the stages of sleep | ||
Erin Gregory edited English subtitles for A walk through the stages of sleep | ||
Camille Martínez accepted English subtitles for A walk through the stages of sleep | ||
Camille Martínez edited English subtitles for A walk through the stages of sleep | ||
Camille Martínez edited English subtitles for A walk through the stages of sleep | ||
Brian Greene edited English subtitles for A walk through the stages of sleep |