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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm Lauren volke Bam and our former host Christian Sager,

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Speaker 1: has another classic episode for you today. The topic is

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Speaker 1: one that plagues me every time I'm on deadline or

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Speaker 1: wanting to finish one more chapter. Why do we sleep? Anyway? Hey,

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Speaker 1: I'm Christian Sager and this is brain Stuff. Here's a

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Speaker 1: quote for you from American light bulb man Thomas Edison.

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Speaker 1: He said sleep is a criminal waste of time inherited

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Speaker 1: from our cave days. Well, like Edison, we hear a

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Speaker 1: brain Stuff hate sleep. That's why we wanted to do

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Speaker 1: this episode to figure out why we have to do it.

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Speaker 1: Normal people spend thirty of their lives asleep, and most

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Speaker 1: are either like us and wish that they didn't have

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Speaker 1: to sleep so they could get more done, or they

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Speaker 1: just want to get a RESTful, uninterrupted night without waking up.

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Speaker 1: Studies actually show that six percent of adults claim to

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Speaker 1: have problems sleeping at least a few nights a week.

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Speaker 1: And here's the thing. Everyone's got to sleep. Yet we

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Speaker 1: still don't know exactly why, but we're going to try

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Speaker 1: to do our best to crack that case. Today that's right.

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Speaker 1: Let's review some theories for why we sleep, what happens

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Speaker 1: when we sleep, and what happens when we don't. Even

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Speaker 1: though we don't know why we sleep, there's all kinds

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Speaker 1: of educated speculation. The most prevalent is that sleep gives

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Speaker 1: our brain a chance to organize and process information, possibly

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Speaker 1: through dreams. Basically, our brain takes all the sensory stimuli

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Speaker 1: we received while we're awake and decides what to keep

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Speaker 1: in where to file it. Everything else gets trashed. It's

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Speaker 1: even possible that our ability to learn tasks actually benefits

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Speaker 1: from quote sleeping on it as a process is better

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Speaker 1: understood after our brain reviews and catalogs it. While most

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Speaker 1: agree with this memory consolidation theory, it's tough to pin

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Speaker 1: down since we all sleep oh differently. And here's another theory.

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Speaker 1: Sleep gives our bodies time to rest and repair. Or

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Speaker 1: how about sleep lowers our energy consumption so we conserve

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Speaker 1: the meals we eat. Other theories delve into the biochemical

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Speaker 1: mechanism of the brain. In a series of experiments on mice,

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Speaker 1: showed that cerebral spinal fluid was pumped around their brains

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Speaker 1: while they slept, expelling waste like molecular detritus and toxic

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Speaker 1: proteins into their livers for breaking down. So do we

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Speaker 1: sleep just to flush the toilet on our cerebral commodes? Well,

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Speaker 1: other sleep researchers were skeptical of the study that I

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Speaker 1: just mentioned, pointing out that there are some big differences

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Speaker 1: between a mouse's brain and humans. So while the answer

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Speaker 1: to why we sleep isn't written in stone, we all

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Speaker 1: know that when we sleep, both our mind and our

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Speaker 1: body feel refreshed. We at least know what's happening when

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Speaker 1: we sleep, right Well, most of us need between seven

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Speaker 1: to nine hours of sleep at night, but that changes

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Speaker 1: during different periods of life. For example, a newborn baby

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Speaker 1: might sleep twenty hours a day, but by the time

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Speaker 1: they're three months old, they recognize the circadian rhythm of

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Speaker 1: sleeping at night and waking up in the morning. And

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Speaker 1: when you're older, like senior citizen older, you can probably

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Speaker 1: get by on only six or seven hours a night.

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Speaker 1: Regardless of how long you're asleep, you must experience both

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Speaker 1: R E M and non R e M stages to sleep. Well.

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Speaker 1: That's rapid eye movement, not the band R E M.

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Speaker 1: From Athens, Georgia, A normal person spends of their sleep

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Speaker 1: in R E M, with each session lasting between five

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Speaker 1: and thirty minutes, and during this time our brain speeds up,

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Speaker 1: our eyes and face might twitch in R e M

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Speaker 1: because we're dreaming. We need around ninety minutes to fulfill

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Speaker 1: a complete cycle of R e M N non r

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Speaker 1: EM sleep, and researchers think this cycle ties sleep back

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Speaker 1: to our ability to process tasks and memories. Recording show

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Speaker 1: that many of the same neurons that fire when we're

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Speaker 1: learning are reactivated during our E M, consolidating the patterns

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Speaker 1: into permanently wired connections. But don't sleep too much more

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Speaker 1: than eight hours can lead to depression or even Parkinson's

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Speaker 1: and heart disease. Of course, if we don't sleep, that's

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Speaker 1: a whole other mess of problems. Rats will actually drop

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Speaker 1: dead if they go more than three weeks without sleep.

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Speaker 1: Us humans, we get lethargic, cranky, and foggy headed at first,

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Speaker 1: almost like we're intoxicated. We might even nod off into

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Speaker 1: micro sleep for a few seconds, and this is what

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Speaker 1: happens after one or two nights without sleep. By day three,

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Speaker 1: we start hallucinating and lose the ability to recognize reality

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Speaker 1: and that's if you're really pushing the boundaries of sleep.

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Speaker 1: Simply failing to get enough sleep is connected to obesity,

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Speaker 1: high blood pressure, a weakened immune system, heart disease, cancer,

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Speaker 1: and diabetes. And it's no big re elation that lots

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Speaker 1: of us don't get enough sleep. We might try to

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Speaker 1: get by on caffeine or nicotine, and alcohol is a

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Speaker 1: good sedative, but it doesn't actually provide the sleep we

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Speaker 1: need for neural processing. So, in the words of the

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Speaker 1: immortal poet Chris Ludicrous bridges, if you're tired, be quiet

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Speaker 1: and go to sleep. Today's episode was written by Ben

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Speaker 1: Bolan and produced by Tyler Clang. To hear more from Ben,

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Speaker 1: tune into his podcast Prediculous History, which is what it

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Speaker 1: says on the tip, but in a really fun way.

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Speaker 1: And of course, for more on this and lots of

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Speaker 1: other answers to annoyingly persistent questions, visit our home planet,

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Speaker 1: how Stuff Works dot com.