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

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followed by a piano recital.

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

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So, what can you do?

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Well, you can drink another cup of coffee

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and spend the next few hours 
cramming and practicing,

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but believe it or not,

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

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and going to sleep.

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Sleep occupies nearly 
a third of our lives,

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

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This neglect is often the result 
of a major misunderstanding.

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Sleep isn't lost time,

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

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Instead, it's a critical function,

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during which your body balances
and regulates its vital systems,

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affecting respiration

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and regulating everything from circulation
to growth and immune response.

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

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Well, not so fast.

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

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with a fifth of your body's 
circulatory blood

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being channeled to it as you drift off.

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And what goes on 
in your brain while you sleep

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is an intensely active period 
of restructuring

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that's crucial for how our memory works.

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At first glance,

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

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19th century psychologist 
Herman Ebbinghaus

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demonstrated that we normally forget
40% of new material

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within the first twenty minutes,

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a phenomenon known
as the forgetting curve.

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But this loss can be prevented 
through memory consolidation,

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the process by which
information is moved

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

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

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known as the hippocampus.

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Its role in long-term memory formation

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was demonstrated in the 1950s
by Brenda Milner

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

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After having his hippocampus removed,

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

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but he was able to learn physical tasks
through repetition.

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Due to the removal of his hippocampus,

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

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What this case revealed,
among other things,

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was that the hippocampus 
was specifically involved

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in the consolidation of
long-term declarative memory,

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

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rather than procedural memory,

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

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

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

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Sensory data is initially transcribed

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

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From there, it travels to the hippocampus,

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which strengthens and enhances 
the neurons in that cortical area.

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Thanks to the phenomenon
of neuroplasticity,

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

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and strengthening the neural network

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

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So why do we remember
some things and not others?

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Well, there are a few ways to influence

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the extent and effectiveness 
of memory retention.

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

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or even stress,

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

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

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you guessed it,

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a good night's sleep.

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Sleep is composed of four stages,

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the deepest of which are known
as slow-wave sleep

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and rapid eye movement.

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EEG machines monitoring
people during these stages

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have shown electrical impulses

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

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which serve as relay stations 
of memory formation.

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

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different types of memories.

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During the non-REM slow-wave sleep,

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declarative memory is encoded 
into a temporary store

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in the anterior part of the hippocampus.

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Through a continuing dialogue 
between the cortex and hippocampus,

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it is then repeatedly reactivated,

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

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

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is associated with the consolidation
of procedural memory.

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So based on the studies,

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going to sleep three hours after 
memorizing your formulas

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

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So hopefully you can see now
that skimping on sleep

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not only harms your long-term health,

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but actually makes it less likely

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

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

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When you think about 
all the internal restructuring

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and forming of new connections
that occurs while you slumber,

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you could even say that proper sleep

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

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ready to face the challenges ahead.