All language subtitles for The.Science.of.Sleep.2016.1080p.WEBRip.x265-RARBG2_English

- [Narrator] For centuries,
we've regarded sleep

as nothing more than a way
to recharge our batteries.

But all of that is changing.

- If sleep wasn't important,

it is probably one of the
most significant mistakes

that evolution ever made.

- [Narrator] Once seen as a blank screen,

the sleeping brain is now emerging

as an energetic and purposeful machine.

- In parts of sleep, the
brain is at least as active

and maybe more active
than it is during waking.

- [Narrator] Around the world,

researchers are attempting to penetrate

the mysterious world of sleep

and decipher its secrets.

Secrets that could change our lives.

- I think that what happens during sleep

permits what happens in the waking brain.

- I'm Doctor Jennifer Gardy.

Join me on a surprising odyssey.

This is remarkable.

(laughs)
Wow.

From playing Chopin to
playing with puppets.

From a city that never sleeps
to an isolation chamber

in the Colorado Rockies,

come with me as I begin
a journey to discover

why we sleep.

(dramatic music)

Deep in the German countryside

lies one of the unique
research centers in the world.

Inside this compound, scientists uncovered

one of the first clues that sleep

might be about more than
just conserving energy.

- [Man] That's very nice.

- [Gardy] Doctor Niels
Rattenborg has spent a decade

researching here at the
Max Planck Institute.

But he isn't your typical sleep scientist.

That's because Dr. Rattenborg
doesn't study humans,

he studies birds.

(flapping wings)

- [Rattenborg] Birds are an
excellent group of animals

in which to study sleep,
because they've evolved

sleep patterns remarkably similar

to those in mammals, including ourselves.

- [Gardy] While all animals sleep,

scientists like Dr. Rattenborg now know

that only birds have
slow wave and REM sleep

just like us.

It's why he's studying
the humble Canada goose.

(honk)

A bird that helped him understand

what evolution revealed about sleep.

- [Rattenborg] Some geese over here.

- [Gardy] Yeah.

And he wanted me to demonstrate

what he was the first to discover.

- [Rattenborg] So, you
see those geese sleeping?

- [Gardy] Yeah.

- You think you can sneak up on them?

- [Gardy] Seems pretty easy.

Sleeping geese, smart human.

(playful music)

They're starting to look.

But these geese prove far
more elusive than I expect.

Whenever I get too close, they wake up

and head for the hills.

I give up, it's impossible!

- [Rattenborg] Some
already went back to sleep.

(both laugh)

- [Gardy] According to Dr. Rattenborg,

the geese evaded me because of
an amazing feat of evolution.

It's called unihemispheric sleep.

Whales, seals, and dolphins do it, too.

While one half of the brain
stays awake and alert,

and one eye open,

the other side of the
brain is in deep sleep

and the corresponding eye is closed.

Given this extraordinary
evolutionary adaptation,

Dr. Rattenborg believes
that what's happening

inside the sleeping brain
must be vital to life itself.

And he's not alone.

- Yeah.

- Dr. Sabine Seehagen often
spends more time on the road

than in her lab at Ruhr
University in Western Germany.

That's because her research subjects

have evolved to spend more
time asleep than awake.

Babies nap for up to 16 hours a day

with waking periods lasting
for just an hour or two.

From the bird research, it was clear

that sleep was playing some vital role.

Dr. Seehagen wanted to find out if it was

helping babies consolidate
and retain memories.

- Infants, they have to learn so much

in the first few years of life

and they develop in such
striking ways, really,

everyday a bit more.

(baby exclaiming)

We were interested to see
whether one function of sleep

might be to facilitate memory processing.

- [Gardy] To discover that, Dr. Seehagen

chooses a task that requires baby Moritz

to remember three interrelated steps.

- [Seehagen] We use a hand puppet

and show them three actions.

We throw them how to take off a mitten,

how to shake the mitten,

and then how to replace the mitten.

- [Gardy] What Dr. Seehagen
is attempting to do

is trigger the memory processing system.

The hippocampus is located
deep within our brain.

This is where specific memories
are encoded and stored.

The neocortex is the large,
outer part of our brain.

It establishes associations
between memories.

Dr. Seehagen and her assistant, Carol,

teach the exact same
memory processing task

to several other babies.

(speaking German)

As soon as the testing is over,

some of the babies stay awake,

while others, like baby Moritz,

go down for a nap.

For Dr. Seehagen, this
is a rare opportunity

to discover whether the sleeping brain

is doing something unique
with the information

it's just taken in.

- We were thinking that
if sleep really helps them

to retain the memories,

then only those infants
who napped right away,

soon after learning, would
remember the actions.

Whereas infants who
would wait with their nap

would not remember the actions.

- [Gardy] Carla hasn't
had a chance to nap yet.

Like all of the babies,
she has just 90 seconds

to repeat the action she saw earlier.

(Carla cooing)

But Carla shows no sign of
remembering the three steps.

(doorbell chimes)

Jonah is another baby who hasn't napped.

- Before we started
our study there was not

very much knowledge about how sleep

might be important for infants' memories

and I'm very interested to see

that infants who wait with the nap,

they did not show signs of remembering

what we've shown them before.

- [Gardy] Across town,
baby Moritz is just up

from his four hour nap.

Now it's his turn.

Without any prompting, he gets to work.

And nails it.

(speaks German)

Dr. Seehagen and her
colleagues conducted this test

on more than 200 infants

with identical results.

- Well, I think it shows
several amazing things

about babies, actually.

Until a few decades ago,

many people even doubted whether infants

can form longer term memory.

But I think our study shows that sleep

seems to play a really fundamental role

in early memory processing.

And I mean, that's a very
fundamental task for infants

to build long term
memories so that they can

use them at a later point.

(classical piano)

- [Gardy] George Ko is in the midst of a

Harvard University tradition.

He's cramming.

(classical piano)

George is trying to learn
Chopin's third Scherzo,

but he's running out of time.

- [Ko] So this week I got
slammed with a lot of work

and I have a performance tomorrow

and I haven't been able to practice much.

- [Gardy] For George, the
solution is a no-brainer.

- [Ko] So I'm probably not
going to sleep tonight.

I'm probably going to hear the
birds chirp in the morning.

- [Gardy] But if babies need
sleep to process memories

and learn, is the same true
for adults like George Ko?

(birdsong)

- Jen, why don't we put you
over here and Jamai, you...

- [Gardy] It's a question
that drives the research

of Doctor Robert Stickgold.

- A really simple test for you guys to do.

- [Gary] Dr. Stickgold is
one of the world's leading

sleep scientists.

- So, put in your first
name or your initials.

- [Gardy] To discover
whether memory processing

is sleep dependent,

Dr. Stickgold needs to
create a complex learning

and motor skill task.

- Now, as soon as you press
another key you're gonna start.

- [Gardy] What he decides on
is a very simplified version

of performing Chopin's Third Scherzo.

- And your job, take your left hand,

put your four fingers on the
keys one, two, three, and four.

You're just gonna type
that number sequence

over and over again,
four one three two four.

Why don't we just have you
both start together now?

- [Gardy] Both Jamai and I
are going to do this task

a second time, but I'll
get to sleep in between

and she won't.

Then we'll see who has
the bigger improvement

in speed and accuracy.

It seems hard to believe
that just one night of sleep

will help me learn the
sequence and make me faster.

But tomorrow will tell.

The next morning, I'm back.

Jamai did her retest yesterday afternoon.

Now it's my turn.

It all comes down to
who has improved more.

- And here you are.

Let's take a look at this.

- Okay.

First, Jamai's results.

- On her second trial with no sleep,

look at here, she's shown
no improvement at all.

- [Gardy] But I was a different story.

- Then look at this,
you just zoom up there.

You're up to 23.

It's a huge improvement in terms of speed.

It's not just academics and students

who are learning all the time.

We're all learning all the time.

Every time you start your car,

you're learning a little bit more about

how long you have to turn the key,

how much you have to press the gas.

Every time you turn a corner,

you're retooling your
accuracy at doing that.

So we're learning all the time
and we don't even know it.

- [Gardy] When we sleep after learning,

our brain consolidates that memory

so we can retrieve it easily.

The more complex the learning task,

the bigger the benefit we get from sleep.

But when we don't sleep enough

that information never even gets filed.

- If you don't get enough sleep

the night after you've learned,

you are not going to show the
potential benefits from sleep.

Even if you sleep all you
want for the rest of the week.

It has to come in that first night.

So what we're learning
is that night by night

we need that sleep or we'd lose.

We'd lose everything.

(classical piano)

- [Gardy] I'm not the
only one who benefited

from some shuteye.

Instead of pulling an all-nighter,

George Ko went to bed.

According to Dr. Stickgold's research,

it was exactly the right thing to do.

- [Stickgold] When I tell
people that we learn a lot

while we're asleep, they think
that's kind of an oxymoron,

that you can't learn while you're asleep.

But in fact, this is just your brain

doing what it evolved to do.

I think the brain carries
out its most sophisticated

memory and brain functions while we sleep.

(classical piano)

(seagulls)

- [Gardy] Given the power
of sleep to help us learn,

scientists at a unique
biosphere in Colorado

wondered whether it also had
the capability to control

how much we eat.

(electronic music)

What better place to find out why we sleep

than in a city that never does?

- Come on!

(cheering)

- If there's one place on Earth

where we're willing to
sacrifice a little bit of sleep

in the hopes of gaining something better,

it's here, Las Vegas.

But this 24 hour town isn't the only place

we're making this kind of trade off.

Without realizing it, we
might be losing something

far more precious than just a few dollars.

Doctor Scott Killgore is
a professor of psychiatry.

But he's also a lieutenant
colonel in the US Army.

Treating soldiers who
fought on the front lines

made Dr. Killgore realize

that they provided a unique
window on the world of sleep.

- We were doing sleep research

and most people were just
focusing in on reaction time

and simple cognitive processes.

But what about this other
side of which choice to make?

You know, do you drop the bomb now,

do you pull the trigger, do
you not pull the trigger?

Because these are not cold decisions.

You don't make them like a computer does.

They're very emotionally
charged situations

and we need more information about how

lack of sleep affects
emotional functioning.

- [Gardy] At the heart of this quest

lies a seeming contradiction.

As it turns out, our
emotions don't cause us

to make bad decisions.

Most of the time they actually
help us make good ones.

Every day I make thousands of choices,

many of them intuitively.

My intuition is guided by
a special type of memory,

an emotional one.

When I experience something,

my brain flags it as either
positive or negative.

When it's time to make a decision,

these emotional memories help me.

- If you watch those
old Star Trek episodes,

you see that in situations
Spock always had

the logical decision making process.

He was like a computer.

So he didn't let emotions
affect his decisions.

Whereas, Kirk, he could tap
into that gut feeling in the

pit of his stomach and make
the right command decision.

- To get inside the brain
where these gut feelings,

these emotional memories are created,

Dr. Killgore came up with
an ingenious experiment

based on a specially
designed gambling task.

Now I'm gonna visit Dr. Killgore

and put that task to the test

and this time, what happens in Vegas

won't be staying in Vegas,
all in the name of science.

- [Killgore] So the
basic idea here is that

there are four decks of cards.

- [Gardy] Okay.

- And your job is to try to
win as much money as possible.

- Ooh!

- And avoid losing any
money in the process.

(beeping)

- Hello, hundred dollars.

But what no one's told me is that

two of the decks will give me big wins

but even bigger losses.

Hmm.

The other two decks deliver small wins

but smaller losses.

(buzzing)

To come out ahead, I've got
to rely on those gut feelings

to help me make the right decisions.

(beeping)

- All right, let's see.

- [Gardy] Turns out I did all right.

I took home 1200 dollars.

- So, this is your baseline.

So now what I want you to do is

to go out and have some fun tonight.

- [Gardy] I can do that.

It's time to get sleep deprived.

(laughing)

Yes!

A little over a century ago,

we slept, on average, nine hours a night.

Today that's down to less than seven.

So my night on the town
is just a quick way

to get me to where most of us already are,

into a state of serious sleep deprivation.

- Jennifer.

Are you still awake?

No sleeping!

- Good morning, Doc.

- Hey, Jen, how are you doing?

- I gotta be honest, I'm really tired.

I think I'm a nine out of
a ten on the tired scale.

- So, did you get hitched?

- (laughs) No.

After 24 hours without sleep,

it's time to do the gambling task again.

Hello, cards.

My old friends.

This time I keep losing track of the decks

and no matter how much I try,
I can't seem to stay focused.

Yesterday I won 1200 bucks,

today I lose 800.

Whoa, I sucked.

The reason can be found here,

in my ventromedial prefrontal cortex.

This is where those emotional
memories are incorporated

with my reasoning to
guide my decision making.

Normally, this area is very active.

But after 24 hours without sleep,

this critical part of my
brain has simply shut down.

- It's not active anymore.

- Yeah.

- So it's not able to turn on
and integrate your emotions

to guide your cognitions and your thoughts

and your decisions.

So your judgements start to get impaired.

You don't know the right answer,

you can't rely on your gut to tell you,

"That's the way I should go."

- Yeah.

It was impossible to tune in onto those,

the good decks and the bad decks.

- Right, the ability to
integrate the emotions

with decision making becomes affected.

So you just flounder.

- What's fascinating is
that Dr. Killgore found this

same impaired judgment in
people with stroke damage

in this exact same part of the brain.

So, in essence, sleep
depravation is almost

a temporary brain injury.

- Yeah, it's basically
very much like you're

brain damaged, but getting
a good night's sleep

can actually reverse the process

and get you back to your baseline.

- Well, that's good because
you know what I could

use right now is my baseline level.

I would really like to get back there.

By delving deep into
our brain, Dr. Killgore

has discovered a direct
relationship between

sleep and the emotional switching system

that guides our decision making.

- We don't understand everything yet,

but so much of the work
that we've been doing

shows that even cutting your sleep down

by a couple of hours

alters the connectivity in the brain

and that in turn affects
your emotional intelligence

and your decision making
and all these areas in life.

- Lights off in three, two, one.

- [Gardy] For two and a half years,

volunteers have lived here
at the University of Colorado

inside a kind of biosphere.

For two weeks at a time,

they sleep, eat, and work in this lab,

isolated from the outside world.

Everything they do is carefully monitored.

They can't take a nap or eat a calorie

without it being measured.

- Hey Chris, let's go
in, let's get started.

- [Chris] All right, sounds good.

- This experiment is the brainchild of

neuroscientist, Doctor Ken Wright.

If sleep deprivation can
cause temporary brain damage,

Dr. Wright wondered if
it could also disrupt

another system regulated by our brain,

the one that controls how much we eat.

- 1.5 billion adults worldwide,

about 150 million school age children

and 43 million preschool children

are overweight or obese.

And over half of our
adult population right now

is not getting that minimum
of seven hours a night.

(on intercom) Hey gang,
just checking in with you.

How's it going tonight so far?

- It's going good.

- [Gardy] Dr. Wright created
this isolation chamber

to take volunteers deep
into sleep deprivation

to see if that would have
an impact on their weight.

For a week now, this group
has been allowed to sleep

nine hours a night.

- Okay, big boy, time to wake up.

- [Gardy] And eat as
much food as they want.

But now it's time for a radical change.

- Yeah, what do you think?

- [Gardy] The volunteers are
about to have their sleep cut

by nearly 50 percent.

For the next week, they'll
get just five hours a night.

- I'll give you a countdown.

I'll dim the lights and
then give you a countdown.

Morning, Jake.

- Good morning.

- Hey, Chris.

How's the subject going today?

- [Gardy] As the 50 percent cut in sleep

begins to take a toll, Dr.
Wright notices a change

in the amount the volunteers are eating.

- So, as we've been following
people's food intake

across these last four days,

we're seeing something remarkable.

Their food intake is going
up, so they're eating more.

- [Gardy] And not just at mealtimes.

The volunteers are also
consuming more snacks.

A lot more.

- What we're starting to see is that

they're eating more after dinner

than they do at any meal
across the entire day.

So it's as if they're
eating four meals a day

rather than just three.

- [Gardy] But what's most
fascinating for Dr. Wright

is the impact on the two
hormones that regulate

how much we eat.

(crunching)

Ghrelin and Leptin are
called the hunger hormones.

Ghrelins signals the brain
when it's time to eat.

Leptin tells the brain
when the body has enough

stored energy and it's
time to stop eating.

The lack of sleep seems
to be causing a meltdown

in this critical part of our
weight regulation system.

As the volunteers eat more,

both Grehlin and Leptin
are telling the brain

it's time to stop eating.

But these messages aren't getting through.

And the amount of weight
gained by the volunteers

is stunning.

- For these participants
after just five days

of getting too little sleep,

they gained .8 kilograms.

It used to be thought
that sleep was just for us

to feel alert during the day

and for us to think clearly
and perform cognitively

at our best,

but unfortunately, when people
are not getting enough sleep,

they eat more.

And sleep loss is known now
to contribute to that risk

of gaining weight.

People recognize that sleep is something

that they can easily give up.

But when they make that choice,

they're not always thinking about

the long term consequences of that.

While they may get sleepy,

the effects of developing heart disease,

the effects of developing obesity,

those are down the road.

- [Gardy] Sleep regulates our weight

and guides our decisions.

But does it have an impact
on another key function

controlled by our brain?

Dreaming.

Scientists are now trying to discover

if our dream world plays an important role

in our waking lives.

Dr. Antonio Zadra can't
remember a time in his life

when he wasn't intrigued by dreams.

- Dreams have always fascinated humankind

and so people have always
been curious about,

since the dawn of history,
about where dreams come from,

how are they formed, do
they have any meaning?

- [Gardy] We spend 52,000
hours of our lives dreaming.

Six solid years.

Dr. Zadra is convinced
that within this vast ocean

of dreaming lies the key to its function.

To unlock the secrets of our dreams,

Dr. Zadra first had to find a way to enter

this mysterious world.

People like artist James Simon
turned out to be the key.

Along with nearly 100 others,

James is part of a unique group.

He is one of Dr. Zadra's dreamers.

- But I'm aware in the
dream that this raven

has a propensity to lunge
for a person's eyes.

As an instinct, as a reflex.

- [Gardy] Dr. Zadra has
collected and assessed

an astonishing 10,000 dreams
from people like James Simon.

He discovered that women
have more nightmares than men

and that we dream about different things,

women about relationships
and men about calamities.

He's also uncovered that
dreams provide a window

into our psychological well being.

- The more negative emotions
you have in your dreams,

the more negative interactions,
aggressive interactions

you have with other
characters in your dreams,

the less happy you tend to be,

or the more anxious or
depressed you tend to be.

- [Gardy] Taken together, Dr.
Zadra's discoveries reveal

that dreams are not the
random and chaotic occurrences

most of us think they are.

- When you look at people's dreams,

you see that there is more order in them

in the sense that you see a continuation

between what's going on during wakefulness

and the content in their dreams.

- [Gardy] Both Dr. Zadra
and sleep scientist

Dr. Robert Stickgold believe
the connection between

our waking lives and our dream world

is a critical clue to
the function of dreams.

- It's when we sleep and
in part when we dream

that we normally figure out
what the events of our day mean.

- [Gardy] Dr. Stickgold
believes this because

of an extraordinary
conversation that takes place

inside our sleeping brain.

When we first go to sleep,
the memories we've accumulated

during the day flow from the hippocampus,

where they've been stored and
assessed, to the neocortex,

where they're associated
with other memories.

The neocortex kicks into
high gear when we dream.

- Then in that first REM cycle,

it's as if the neocortex
says back to the hippocampus,

"Oh, that's like what
happened last month."

It's as if now the front of the brain

is telling the hippocampus,
"Okay, you know what?

Those details aren't important."

Or, "Those details are important."

And telling the hippocampus
what to do with that information

and also working out
itself, in the neocortex,

seeing how things fit together.

- To confirm that dreaming
really does help us

associate memories in
order to give them meaning,

Dr. Stickgold created a
series of unique tests.

In one expermient, Dr. Stickgold
trained a group of people

to go through a maze.

Afterwards, half had
a nap and half didn't.

Later that day, people came
back and ran the maze again.

Those that had napped found
the exit more quickly.

But what got Dr. Stickgold really excited

were those people who both
napped and dreamt about the maze.

They found the exit ten times faster.

- I think what we're seeing now

is that dreams in fact are a reflection

of the kind of processing
that the brain does

while we sleep.

Just us being conscious while we're asleep

and conscious of things that our brain is

constructing as stories.

And so we're really
watching over the shoulder

of a film editor.

But if you just watch
the screen of the editor,

it looks crazy, like a dream.

Things are juxtaposed
from different places,

you don't know why
they're being juxtaposed.

Things are being replayed.

It's as if the brain,
while we're dreaming,

is trying to see how things fit together.

- [Gardy] According to Dr. Stickgold,

this is my sleeping brain giving meaning

to the events of my life.

Dr. Zadra believes if patterns
can be found in this chaos,

they have the power to reveal something

about my psychological well being.

Before I arrived at his lab,

he asked me to keep a dream diary.

So for the last six weeks, I've
been writing down my dreams.

- I had a chance to read over your dreams

and try to quantify their contents,

in terms of the characters
we see, the settings,

the social interactions.

- [Gardy] Dr. Zadra knows
very little about me,

only that I'm a TV host.

But right away he uncovers
my anxieties about

solving problems in a
dream about a leaking pipe.

- So there's all the water,
which is a misfortune,

not your fault, but you still--

- I have to fix it.
- Unplug it.

You still get the towels,
you still mop it up.

- Yeah.

- And so, um, you're still trying somehow

to minimize the damage or to try to

bring it under control to
whatever extent you can.

- [Gardy] Dr. Zadra also totally nails

that I worry about outward appearances

and about the value of my work.

But there's one revelation from my dreams

that catches me completely off guard.

- In over half of your dreams,

there are references to animals.

So the fact that there are many animals

and the way you interact with them,

I would say that you're concerned about

animals' well beings.

Not just your dog or your cat,
if you happen to have one,

but that the well being
of animals is something

that is dear to you, generally.

- This is crazy, you're
making me all misty

and teary-eyed, because
this is remarkable.

Absolutely remarkable.

I do, I have a cat, I have a
dog, I love them to pieces,

I love all animals.

This is remarkable.

(laughs)
Wow.

- I think this entire exercise for Jen

probably made her much more appreciative

of the power of dreams

and again of the order
that we can find in dreams

and the psychological meanings
we can find in dreams.

So there's a relationship over time

about how well people are functioning

and how well they feel

and the content and patterns
in their dreams as well.

- [Gardy] If sleep allows us to enter

the mysterious world of dreams,
could it also be involved

in one of the brain's
greatest unsolved puzzles?

Every night, virtually
every species on the planet

goes to sleep.

For the first time, we're
beginning to understand

how this nightly ritual regulates

almost every aspect of our waking lives.

But there's one discovery
that's eluded researchers.

Uncovering the core
biological function of sleep.

For neuroscientist Doctor Jeff Iliff

and a team from Rochester University,

their quest begins with a baffling clue

about a protein that's the key culprit

in Alzheimer's disease.

- So there's a protein
called amyloid beta,

which is made in the brain all the time.

Now, when you're awake,
amyloid beta levels

in the brain go up

and when you're asleep during the night,

amyloid beta levels in the brain go down.

- [Gardy] The question is why.

To find out, Dr. Iliff hopes to do

what few sleep scientists
have ever done before.

Look directly into the sleeping brain.

- [Iliff] We have a very powerful
and specialized microscope

that can actually shine through the skull

into the living brain while
it's doing all of its processes.

- [Gardy] This is the world
of the sleeping brain.

What Dr. Iliff sees is a
complex network of blood vessels

that dive deep into the brain's center,

supplying nutrients and
oxygen to its cells.

But there's something else,
something completely unexpected.

At night, the brain begins to change.

- [Iliff] Something's happening
within the tissue itself.

The brain's cells, the
support cells in the brain,

are actually shrinking.

- Dr. Iliff believes the team has

stumbled upon a clue that may be connected

to one of the brain's
most puzzling mysteries.

How it cleans itself.

Like the tributaries of a river,

our body relies on the circulatory system

to bring nutrients to
its trillions of cells.

But these cells also produce waste.

In a river, sediment
settles to the bottom,

but in our bodies, we have lymph vessels

to collect the waste and carry
it through our bloodstream

to places like the liver,
where it's eliminated.

But there's one part of the body

the lymph vessels don't go
to and that's the brain.

So how does the brain clean itself?

Dr. Iliff believes the answer is connected

to the mysterious changes he observed

taking place inside the
brain while we sleep.

During the day, the brain
is protected by a sac

filled with fluid that surrounds it.

But as Dr. Iliff discovers,
at night this sac empties

and the fluid filters through the brain.

- [Iliff] What was happening was that

the fluid was piggybacking,
using the structure

of the blood vessels to get
access to the entire brain.

- [Gardy] But it's what the
fluid does that provides

Dr. Iliff and his team with
an extraordinary breakthrough.

- [Iliff] The fluid that's
on the outside of the brain,

as it flows along those blood vessels

and through the brain tissue,

it's doing the most amazing thing.

It's clearing away, washing away,

the waste particles in the
spaces between the brain's cells.

- Wow.

We can't multitask enough during the day,

we have to set something aside.

Housekeeping happens at night.

- Yeah, it's a very
clever way to do, really,

two things with the same structure,

both provide nutrients
and clear away the waste.

But it's unique.

No other part of the body
uses a plan like this

to do these two things.

- It's a brains cleaning system.

- It is.

It's sort of like a
dishwasher for the brain.

- But Dr. Iliff and his
team aren't done yet.

There's still the
question of amyloid beta,

the protein that started
them on this journey.

Amyloid beta is one of the waste products

produced by the brain.

It's also the same protein that builds up

in the brains of people suffering
from Alzheimer's disease.

When Dr. Iliff started this research,

he saw levels of amyloid
beta rise in the brain

during the day and drop at night.

Now he knows why.

The brain is washing away
this dangerous protein

while we sleep.

So, circling back to the beginning,

what does this tell you about Alzheimer's?

- Well, it tells us that this process

may be part of what's going wrong

in patients with Alzheimer's disease.

Worsening sleep quality and sleep duration

are both associated with
worsening amyloid plaque burden,

so more amyloid beta
building up in the brain.

And so the failure of the brain to sort of

keep its house clean and
clear away these things

that it needs to be
clearing away during sleep

may actually be setting the stage

for the development of diseases
like Alzheimer's disease.

- [Gardy] For the first
time, we're realizing

that our sleeping brain is the foundation

of almost everything we do.

- I think sleep is fundamental to life.

We're recognizing the importance of sleep

for our whole body.

Sleep effects everything.

- I think that the occurrence
of what happens during sleep

permits what happens in the waking brain

and that you could not
have all of the magic

of the waking brain
without all of the mystery

of the sleeping brain.

- We create the meaning of
our lives while we sleep.

And that's phenomenal.

(electronic music)

(thwack)

(applause)