- In early 2022, 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