action star and Hollywood legend Bruce Willis

stepped away from acting.

This piece of news was particularly poignant

because of the reason for his retirement: aphasia.

A language disorder

that affects a person's ability to communicate,

often caused by strokes, brain injuries, tumors,

or in Willis's case, dementia.

Even though the word language comes

from the Latin for tongue,

language is really more related to the brain

than any other part of the body.

It's where language happens.

Whether you're shaping words with your mouth,

signing them with your hands,

or writing them on paper,

the bulk of the work is going on up here.

While there is no one part of the brain

that handles everything speech-related,

there are some areas that are more involved than others.

Scientists have known this long before

the development of MRIs

and other brain scanning technologies. How?

Through the study and observation

of patients who have experienced language impairments

due to brain damage.

By determining what has been lost or impaired,

neuroscientists have been better able to understand

how our brains process language

and what language really is.

And now my brain-language connection

will communicate that to you.

I'm Dr. Erica Brozovsky,

and this is "Otherwords."

(upbeat music)

To learn more about the relationship

between language and the brain,

I spoke with Dr. Alexander Tan,

a pediatric neuropsychologist

with expertise in the assessment

of neurological and neurodevelopmental disorders

in children and adolescents.

So you're a neuropsychologist.

What is neuropsychology?

- The definition of neuropsychology literally is

the study of brain and behavior and that relationship.

So as a pediatric neuropsychologist,

we do checkups on different brain functions,

like attention, memory, visual perception, language.

And then using those results,

we can assess for brain disorders

and make sure that we are getting children the treatments

and supports that they might need

and track their development or their recovery over time.

- When it comes to the connection

between language and the brain,

the first answers were discovered in sort of a curious way.

Prior to technological advances in neuroimaging,

like functional MRIs,

doctors couldn't see what was happening in the brain

and observe what areas lit up with various stimuli.

The only way to look at the brain was by opening it up.

In the 19th century,

physicians Paul Broca and Carl Wernicke

separately discovered two regions of the brain

through conducting autopsies on aphasic patients.

- [Dr. Tan] Dr. Broca and Dr. Wernicke were able

to locate specific parts of the brain

that have resulting impacts on their ability to

either express language or to comprehend language.

And those parts, now referred to as Broca's area

and Wernicke's area, are in the left frontal

or left temporal lobe, respectively.

And that was one of the first signals to us

that the left hemisphere is dominant for language.

- For more than 95% of right-handed people

and 60% of left-handed people,

the left hemisphere is dominant for language.

But that's not to say

that the language party is exclusively on the left side.

- Now that we've had more advancements in technology,

different kinds of imaging techniques,

we now are seeing that language actually involves a lot

of different parts of the brain,

including, you know, implicating all four lobes,

the gray matter and the white matter,

cortical and subcortical structures.

It's very much a complex ability

that involves communication and coordination

between a lot of different parts of the brain.

- When you see an image, say, this one,

you think, "Okay, yeah, sure, it's a ball,

or a car, or a unicorn."

But that's just the result.

Let's backtrack to what happened on the inside.

First, you process the visual input

so that you could recognize the object.

Then you have to convert the input into a semantic concept.

From there, you search through your mental Rolodex

of abstract representations

and pick the concept matching word.

Finally, you articulate the phonemes

that make up that word.

And if just one step doesn't work properly,

you might not be able to recognize the object,

or know what it's for,

or find the word you need,

or communicate the word to anyone else.

What is aphasia, first of all, and what causes it?

- So aphasia is essentially

an impairment in language abilities.

And it is typically caused by strokes,

brain injuries that affect certain parts of the brain,

or some kind of neurodegenerative condition,

like dementias or Alzheimer's disease.

- [Dr. Brozovsky] The two most common types of aphasias

are the ones named after Broca and Wernicke.

Damage to Broca's area may cause Broca's aphasia,

or expressive aphasia,

which means you can generally understand others

but have difficulty getting your words out.

It might be limited to single words or short phrases.

On the other hand, someone suffering

from Wernicke's aphasia,

or receptive aphasia,

will have trouble understanding language, even their own,

but is still capable of fluid, competent speech.

They may talk in long, nonsensical,

yet grammatically correct sentences.

- [Dr. Tan] There's a white matter highway

between Broca's area and Wernicke's area called

the arcuate fasciculus that can be communicates

between the two.

And so sometimes when there's impact to that,

there's something called conduction aphasia

where our expression is intact,

our comprehension is intact,

but because we can't integrate the two,

then it's hard for us to repeat language that we hear.

- In other cases, extensive deterioration of the brain,

such as various types of dementia,

can lead to global aphasia

where all three factors,

fluency, understanding, and repetition are impaired.

And what kind of treatments are available

for people who are experiencing aphasia?

- Our main treatment for the aphasia specifically

usually focuses on rehabilitation

in the form of speech and language therapy.

We always want to have supportive treatments in place

for some of the side effects.

Individuals with aphasia

or at risk for things like depression and social isolation,

you know, our brains deteriorate faster

with the absence of social connection,

so it's really important for individuals with aphasia

and for those supporting them to find,

you know, alternate ways to communicate with them

and continue to integrate them socially.

And just making sure that we're patient with them

as they try to find the words.

- We know that the brain changes

over the course of our lives

and it generally comes to maturity

in the mid to late twenties.

During childhood, our neuroplasticity,

or the ability of networks in the brain

to grow and change,

is at its highest levels.

- If, for example, children have seizures on the left side,

there's this crowding effect

that we sometimes observe

where language kind of reorganizes

onto the right side of the brain to preserve itself

and sometimes crowds out the other functions

that were typically associated with the right side.

So sometimes resulting in weaknesses

to non-verbal and visual skills.

- So is the brain prioritizing language

above significant other functions in general?

Is that something that the brain generally prioritizes?

- Yes, the brain does tend

to try to preserve language abilities.

You know, language is so important

to be able to communicate,

to learn, to navigate the world socially.

The brain will reorganize however it can

to make sure language function is preserved.

- Is it possible to improve your neuroplasticity

as an adult?

- Yeah, sure, there's always ways that,

you know, the typical things that our doctors tell us

that we never listen to, right?

Making sure that we're really taking care of our sleep,

our exercise, our diet.

Learning a new language is a really great one

that really forces our brain

to activate all those parts of the brain

that are really important for not just language learning

but also code switching and executive functioning.

- The brain is an incredibly capable and resilient machine,

and scientists are learning new things

about the brain-language connection every day.

What is something you've learned about the human brain

over the course of your career

that you think everyone should know?

- The number one thing I've learned about the brain

is just that there's always more to learn about the brain.

We've made big, you know, very large strides

in terms of understanding how parts of the brain correlate

with brain function,

but there are just so many answers that we still don't have,

and that's just what makes it eternally fascinating to me.

- Language is one of the things that makes us human,

and because of that,

it is invaluable to us as a species.

Any loss of language or communication ability is a tragedy.

But by the groundwork laid through studying language

through the lens of brain damage,

we've come to understand the pieces

that make up human language,

how injury affects them,

and how to apply that information

to improve the lives of those who are affected.

You may also remember from a previous episode

that swearing relies just as much

on the right side of the brain.

So don't expect someone with left-side brain image

to swear any left.

Left? Oh no! (laughs) (crew laughs)

(bright music)