The benefits of a good night's sleep - Shai Marcu

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It’s 4am, and the big test is in 8 hours. You’ve been studying for days, but you still don’t feel ready. Should you drink another cup of coffee and spend the next few hours cramming? Or should you go to sleep? Shai Marcu defends the latter option, showing how sleep restructures your brain in a way that’s crucial for how our memory works.

Lesson by Shai Marcu, animation by Javier Saldeña.

It's 4 a.m.,
and the big test is in eight hours,

followed by a piano recital.

You've been studying and playing for days,
but you still don't feel ready for either.

So, what can you do?

Well, you can drink another cup of coffee

and spend the next few hours
cramming and practicing,

but believe it or not,

you might be better off closing the books,
putting away the music,

and going to sleep.

Sleep occupies nearly
a third of our lives,

but many of us give surprisingly
little attention and care to it.

This neglect is often the result
of a major misunderstanding.

Sleep isn't lost time,

or just a way to rest
when all our important work is done.

Instead, it's a critical function,

during which your body balances
and regulates its vital systems,

affecting respiration

and regulating everything from circulation
to growth and immune response.

That's great, but you can worry about
all those things after this test, right?

Well, not so fast.

It turns out that sleep
is also crucial for your brain,

with a fifth of your body's
circulatory blood

being channeled to it as you drift off.

And what goes on
in your brain while you sleep

is an intensely active period
of restructuring

that's crucial for how our memory works.

At first glance,

our ability to remember things
doesn't seem very impressive at all.

19th century psychologist
Herman Ebbinghaus

demonstrated that we normally forget
40% of new material

within the first twenty minutes,

a phenomenon known
as the forgetting curve.

But this loss can be prevented
through memory consolidation,

the process by which
information is moved

from our fleeting short-term memory
to our more durable long-term memory.

This consolidation occurs with the help
of a major part of the brain,

known as the hippocampus.

Its role in long-term memory formation

was demonstrated in the 1950s
by Brenda Milner

in her research with
a patient known as H.M.

After having his hippocampus removed,

H.M.'s ability to form new short-term memories
was damaged,

but he was able to learn physical tasks
through repetition.

Due to the removal of his hippocampus,

H.M.'s ability to form long-term memories
was also damaged.

What this case revealed,
among other things,

was that the hippocampus
was specifically involved

in the consolidation of
long-term declarative memory,

such as the facts and concepts
you need to remember for that test,

rather than procedural memory,

such as the finger movements
you need to master for that recital.

Milner's findings, along with work
by Eric Kandel in the 90's,

have given us our current model
of how this consolidation process works.

Sensory data is initially transcribed

and temporarily recorded in the neurons
as short-term memory.

From there, it travels to the hippocampus,

which strengthens and enhances
the neurons in that cortical area.

Thanks to the phenomenon
of neuroplasticity,

new synaptic buds are formed,
allowing new connections between neurons,

and strengthening the neural network

where the information will be returned
as long-term memory.

So why do we remember
some things and not others?

Well, there are a few ways to influence

the extent and effectiveness
of memory retention.

For example, memories that are formed
in times of heightened feeling,

or even stress,

will be better recorded due to
the hippocampus' link with emotion.

But one of the major factors contributing
to memory consolidation is,

you guessed it,

a good night's sleep.

Sleep is composed of four stages,

the deepest of which are known
as slow-wave sleep

and rapid eye movement.

EEG machines monitoring
people during these stages

have shown electrical impulses

moving between the brainstem,
hippocampus, thalamus, and cortex,

which serve as relay stations
of memory formation.

And the different stages of sleep
have been shown to help consolidate

different types of memories.

During the non-REM slow-wave sleep,

declarative memory is encoded
into a temporary store

in the anterior part of the hippocampus.

Through a continuing dialogue
between the cortex and hippocampus,

it is then repeatedly reactivated,

driving its gradual redistribution
to long-term storage in the cortex.

REM sleep, on the other hand, with
its similarity to waking brain activity,

is associated with the consolidation
of procedural memory.

So based on the studies,

going to sleep three hours after
memorizing your formulas

and one hour after practicing your scales
would be the most ideal.

So hopefully you can see now
that skimping on sleep

not only harms your long-term health,

but actually makes it less likely

that you'll retain all that knowledge
and practice from the previous night,

all of which just goes to affirm
the wisdom of the phrase, "Sleep on it."

When you think about
all the internal restructuring

and forming of new connections
that occurs while you slumber,

you could even say that proper sleep

will have you waking up every morning
with a new and improved brain,

ready to face the challenges ahead.