dreams,

emotions,

and memories.

It's what makes us who we are.

But, there is still a lot that we don't know about the brain.

Scientists have worked for years

on trying to understand the human brain

using techniques like EEG and FMRI,

where we scan the brain from the outside.

But what if we could look inside the brains of humans

and watch them as they work?

Well, now we can

by looking at the brains of people

who are already going through surgery for clinical reasons,

like curing epilepsy.

Epilepsy is a disease

in which a faulty part of the brain

starts working spontaneously for no apparent reason.

It's like an earthquake

but inside your head.

There's no way to know in advance

when a seizure will occur,

so the patients are always at risk

of unexpectedly losing control.

There are drugs that treat epilepsy,

but these don't always work.

Some patients who don't respond well to the drugs

can undergo a different treatment

where the faulty part in their brain,

the part that starts the seizures,

is surgically removed.

The challenge is knowing which part to take out.

How do you figure out which bit of the brain is faulty?

In order to find the exact location of the seizure onset,

doctors embed electrodes directly into the patient's brain

around the suspected seizure center.

The patient then stays in the hospital for a few days,

waiting to have a seizure

with the electrodes constantly recording

the activity inside his or her brain.

Yes, now we want the patient to have a seizure

so doctors can use the embedded electrodes

to measure it and learn exactly where its origin was.

After doctors are sure where the seizures

come from in the brain,

they can take the electrodes out.

Now they know what part of the brain they can remove

in order to cure the patient.

These brain electrodes can tell us

more than just where the seizures happen.

Based on where the doctors place the electrodes in the brain,

we can ask questions about what the brain does.

Sometimes we find one cell that starts bursting in activity

every time the patient sees a particular picture,

for example, a picture of Marilyn Monroe.

See, every time the patient sees Marilyn Monroe,

some specific cells fire in the brain.

You can now know when the patient is thinking of Marilyn Monroe

just by listening to these cells fire.

When we find one or a few of these cells with each patient,

we can then do all kinds of fancy things.

For example, we can connect the recording electrode

to a cursor on a screen

and have the patient move the cursor left or right

just by thinking of things.

This can help people

who lost the ability to move their hands,

like people with spinal cord injuries or wounded soldiers,

by having them control a prosthetic arm

directly with their brain.

Our brain is a brilliant device

which can make predictions about the future.

For example, we can all know

which word will appear at the end of this...

sentence.

The brain can solve complicated problems,

imagine the entire universe,

and grasp concepts such as infinity

or unicorns.

The brain produces complex emotions like love or jealousy,

it's what makes us creative and curious,

and it can even contemplate about itself.

And the brain is the organ we use to study the brain.

I think that the brain is the most beautiful organ in our body,

but then I ask myself,

"Which organ is making me think that?"