[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.13,0:00:02.94,Default,,0000,0000,0000,,Sleep is perhaps the\Nsingle most effective thing
Dialogue: 0,0:00:02.96,0:00:05.07,Default,,0000,0000,0000,,that we can do each and every day
Dialogue: 0,0:00:05.10,0:00:08.82,Default,,0000,0000,0000,,to reset the health\Nof our brain and our body.
Dialogue: 0,0:00:08.84,0:00:12.76,Default,,0000,0000,0000,,And by understanding a little bit more\Nabout what sleep is,
Dialogue: 0,0:00:12.78,0:00:17.24,Default,,0000,0000,0000,,perhaps we can get the chance to improve\Nboth the quantity and the quality
Dialogue: 0,0:00:17.26,0:00:18.27,Default,,0000,0000,0000,,of our sleep.
Dialogue: 0,0:00:18.30,0:00:20.14,Default,,0000,0000,0000,,[Sleeping with Science]
Dialogue: 0,0:00:20.14,0:00:21.80,Default,,0000,0000,0000,,(Music)
Dialogue: 0,0:00:23.13,0:00:25.81,Default,,0000,0000,0000,,So, exactly what is sleep?
Dialogue: 0,0:00:26.27,0:00:28.91,Default,,0000,0000,0000,,Well, sleep, at least in human beings,
Dialogue: 0,0:00:28.94,0:00:31.93,Default,,0000,0000,0000,,is subdivided into two main types.
Dialogue: 0,0:00:31.95,0:00:35.31,Default,,0000,0000,0000,,On the one hand, we have\Nnon-rapid eye movement sleep,
Dialogue: 0,0:00:35.33,0:00:37.03,Default,,0000,0000,0000,,or non-REM sleep for short.
Dialogue: 0,0:00:37.05,0:00:38.22,Default,,0000,0000,0000,,But on the other hand,
Dialogue: 0,0:00:38.24,0:00:42.23,Default,,0000,0000,0000,,we have rapid eye movement\Nsleep, or REM sleep.
Dialogue: 0,0:00:42.25,0:00:45.66,Default,,0000,0000,0000,,And non-REM sleep has been\Nfurther subdivided
Dialogue: 0,0:00:45.68,0:00:47.84,Default,,0000,0000,0000,,into four separate stages,
Dialogue: 0,0:00:47.86,0:00:51.87,Default,,0000,0000,0000,,unimaginatively called\Nstages one through four,
Dialogue: 0,0:00:51.89,0:00:54.41,Default,,0000,0000,0000,,increasing in their depth of sleep.
Dialogue: 0,0:00:54.43,0:00:58.23,Default,,0000,0000,0000,,And as we go into those light stages\Nof non-REM sleep,
Dialogue: 0,0:00:58.25,0:01:01.03,Default,,0000,0000,0000,,your heart rate starts to decrease,
Dialogue: 0,0:01:01.05,0:01:03.19,Default,,0000,0000,0000,,your body temperature starts to drop
Dialogue: 0,0:01:03.21,0:01:07.24,Default,,0000,0000,0000,,and your electrical brain wave activity\Nstarts to slow down.
Dialogue: 0,0:01:07.26,0:01:11.42,Default,,0000,0000,0000,,But as we move into deeper\Nnon-rapid eye movement sleep,
Dialogue: 0,0:01:11.44,0:01:13.32,Default,,0000,0000,0000,,stages three and four,
Dialogue: 0,0:01:13.34,0:01:16.33,Default,,0000,0000,0000,,now all of a sudden the brain erupts
Dialogue: 0,0:01:16.35,0:01:20.06,Default,,0000,0000,0000,,with these huge, big,\Npowerful brain waves.
Dialogue: 0,0:01:20.47,0:01:25.34,Default,,0000,0000,0000,,The body is actually recharged\Nin terms of its immune system.
Dialogue: 0,0:01:25.36,0:01:29.91,Default,,0000,0000,0000,,We also get this beautiful overhaul\Nof our cardiovascular system.
Dialogue: 0,0:01:30.30,0:01:32.71,Default,,0000,0000,0000,,And, in fact, upstairs in the brain,
Dialogue: 0,0:01:32.73,0:01:35.98,Default,,0000,0000,0000,,deep non-REM sleep\Nwill help consolidate memories
Dialogue: 0,0:01:36.00,0:01:39.68,Default,,0000,0000,0000,,and fixate them into the neural\Narchitecture of the brain.
Dialogue: 0,0:01:39.70,0:01:42.04,Default,,0000,0000,0000,,So that's non-REM sleep.
Dialogue: 0,0:01:42.06,0:01:44.53,Default,,0000,0000,0000,,But let's come on to REM sleep,
Dialogue: 0,0:01:44.55,0:01:46.74,Default,,0000,0000,0000,,which is the other main type of sleep.
Dialogue: 0,0:01:46.76,0:01:51.25,Default,,0000,0000,0000,,And it's during REM sleep\Nwhen we principally have the most vivid,
Dialogue: 0,0:01:51.27,0:01:54.14,Default,,0000,0000,0000,,the most hallucinogenic types of dreams.
Dialogue: 0,0:01:54.16,0:01:58.24,Default,,0000,0000,0000,,The brain wave activity\Nactually starts to speed up again.
Dialogue: 0,0:01:58.26,0:02:04.88,Default,,0000,0000,0000,,It's during REM sleep that we receive\Nalmost a form of emotional first aid.
Dialogue: 0,0:02:04.90,0:02:09.38,Default,,0000,0000,0000,,And it's also during REM sleep\Nwhere we get a boost for creativity,
Dialogue: 0,0:02:09.40,0:02:12.18,Default,,0000,0000,0000,,that it stitches information together
Dialogue: 0,0:02:12.20,0:02:14.71,Default,,0000,0000,0000,,so that we wake up with solutions
Dialogue: 0,0:02:14.73,0:02:18.18,Default,,0000,0000,0000,,to previously difficult problems\Nthat we were facing.
Dialogue: 0,0:02:18.20,0:02:20.56,Default,,0000,0000,0000,,Coming back to these two types of sleep,
Dialogue: 0,0:02:20.58,0:02:24.84,Default,,0000,0000,0000,,it turns out that non-REM\Nand REM will play out
Dialogue: 0,0:02:24.86,0:02:28.62,Default,,0000,0000,0000,,in a battle for brain domination\Nthroughout the night,
Dialogue: 0,0:02:28.64,0:02:33.05,Default,,0000,0000,0000,,and that cerebral war\Nis going to be won and lost
Dialogue: 0,0:02:33.07,0:02:34.84,Default,,0000,0000,0000,,every 90 minutes,
Dialogue: 0,0:02:34.86,0:02:38.06,Default,,0000,0000,0000,,and then it's going to be\Nreplayed every 90 minutes.
Dialogue: 0,0:02:38.54,0:02:44.25,Default,,0000,0000,0000,,And what this produces is a standard\Ncycling architecture of human sleep,
Dialogue: 0,0:02:44.28,0:02:46.18,Default,,0000,0000,0000,,a standard 90-minute cycle.
Dialogue: 0,0:02:46.76,0:02:48.49,Default,,0000,0000,0000,,But what's different, however,
Dialogue: 0,0:02:48.51,0:02:54.36,Default,,0000,0000,0000,,is that the ratio of non-REM to REM\Nwithin those 90-minute cycles
Dialogue: 0,0:02:54.38,0:02:57.36,Default,,0000,0000,0000,,changes as we move across the night,
Dialogue: 0,0:02:57.38,0:02:59.83,Default,,0000,0000,0000,,such that in the first half the night,
Dialogue: 0,0:02:59.85,0:03:02.61,Default,,0000,0000,0000,,the majority of those 90-minute cycles
Dialogue: 0,0:03:02.63,0:03:06.01,Default,,0000,0000,0000,,are comprised of lots\Nof deep non-REM sleep,
Dialogue: 0,0:03:06.03,0:03:09.97,Default,,0000,0000,0000,,particularly stages three and four\Nof non-REM sleep.
Dialogue: 0,0:03:09.99,0:03:13.35,Default,,0000,0000,0000,,But as we push through\Nto the second half of the night,
Dialogue: 0,0:03:13.37,0:03:17.48,Default,,0000,0000,0000,,now that seesaw balance\Nactually shifts over,
Dialogue: 0,0:03:17.50,0:03:20.80,Default,,0000,0000,0000,,and instead, most of those\N90-minute cycles
Dialogue: 0,0:03:20.82,0:03:25.53,Default,,0000,0000,0000,,are comprised of a lot more\Nrapid eye movement sleep, or dream sleep,
Dialogue: 0,0:03:25.55,0:03:28.51,Default,,0000,0000,0000,,as well as stage-two non-REM sleep,
Dialogue: 0,0:03:28.53,0:03:30.70,Default,,0000,0000,0000,,that lighter form of non-REM sleep.
Dialogue: 0,0:03:30.72,0:03:34.27,Default,,0000,0000,0000,,And it turns out\Nthat there are implications
Dialogue: 0,0:03:34.29,0:03:38.02,Default,,0000,0000,0000,,for understanding how sleep\Nis structured in this way.
Dialogue: 0,0:03:38.05,0:03:42.79,Default,,0000,0000,0000,,Let's take someone who typically\Ngoes to bed at 10pm,
Dialogue: 0,0:03:42.81,0:03:44.82,Default,,0000,0000,0000,,and they wake up at 6am,
Dialogue: 0,0:03:44.84,0:03:47.07,Default,,0000,0000,0000,,so they have an eight-hour sleep window.
Dialogue: 0,0:03:47.49,0:03:49.100,Default,,0000,0000,0000,,But this morning,\Nthey have to wake up early
Dialogue: 0,0:03:50.02,0:03:52.34,Default,,0000,0000,0000,,for an early morning meeting,
Dialogue: 0,0:03:52.36,0:03:54.43,Default,,0000,0000,0000,,or they want to get\Na jump start on the day
Dialogue: 0,0:03:54.45,0:03:55.82,Default,,0000,0000,0000,,to get to the gym.
Dialogue: 0,0:03:55.84,0:03:59.80,Default,,0000,0000,0000,,And as a consequence, they have to wake up\Nat 4am in the morning,
Dialogue: 0,0:03:59.82,0:04:02.04,Default,,0000,0000,0000,,rather than 6am in the morning.
Dialogue: 0,0:04:02.06,0:04:04.38,Default,,0000,0000,0000,,How much sleep have they actually lost?
Dialogue: 0,0:04:04.40,0:04:07.03,Default,,0000,0000,0000,,Two hours out of\Nan eight-hour night of sleep
Dialogue: 0,0:04:07.05,0:04:11.11,Default,,0000,0000,0000,,means that they've lost\N25 percent of their sleep.
Dialogue: 0,0:04:11.56,0:04:13.77,Default,,0000,0000,0000,,Well, yes and no.
Dialogue: 0,0:04:13.80,0:04:17.12,Default,,0000,0000,0000,,They have lost 25 percent\Nof all of their sleep,
Dialogue: 0,0:04:17.14,0:04:21.53,Default,,0000,0000,0000,,but because REM sleep comes\Nmostly in the second half of the night
Dialogue: 0,0:04:21.55,0:04:23.55,Default,,0000,0000,0000,,and particularly in those last few hours,
Dialogue: 0,0:04:23.57,0:04:28.93,Default,,0000,0000,0000,,they may have lost perhaps\N50, 60, maybe even 70 percent
Dialogue: 0,0:04:28.96,0:04:30.75,Default,,0000,0000,0000,,of all of their REM sleep.
Dialogue: 0,0:04:30.77,0:04:36.04,Default,,0000,0000,0000,,So there are real consequences\Nto understanding what sleep is
Dialogue: 0,0:04:36.06,0:04:37.79,Default,,0000,0000,0000,,and how sleep is structured.
Dialogue: 0,0:04:37.81,0:04:42.07,Default,,0000,0000,0000,,And we'll learn all about the benefits\Nof these different stages of sleep
Dialogue: 0,0:04:42.09,0:04:45.61,Default,,0000,0000,0000,,and the detriments that happen\Nwhen we don't get enough of them
Dialogue: 0,0:04:45.64,0:04:47.28,Default,,0000,0000,0000,,in subsequent episodes.