< Meet the teen changing how neuroscientists think about brain plasticity

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE from NPR.

REGINA BARBER, HOST:

Hey, SHORT WAVE-rs. Regina Barber here with Jon Hamilton, NPR's resident brain science guy and curator of terrible jokes. Hey, Jon.

JON HAMILTON, BYLINE: Oh, Gina. I am going to try to move past my hurt and introduce you to somebody who tells a lot better jokes than I do.

BARBER: Great.

HAMILTON: Her name is Mora Leeb.

Hi, Mora. How are you doing?

MORA LEEB: Good. How are you?

HAMILTON: Mora is 15. And in a lot of ways, she's pretty much of a typical teenager. I mean, she likes to play tennis. She likes to play soccer. She gets her nails done. And she loves to tell jokes.

MORA: How do you make a hot dog stand?

HAMILTON: I don't know. How do you?

MORA: Take away its chair.

BARBER: She's good. You could learn from her, Jon.

HAMILTON: Yeah, thanks. But, you know, the reason we're talking about Mora today is that she has a really unusual brain. So about two months before she was born, she had a massive stroke. Nobody realized at the time. And her mom, Ann Leeb, says her daughter seemed like a typical baby at first. I mean, she smiled. She rolled over.

ANN LEEB: And then in the holiday season of 2007, all of these milestones sort of stopped.

HAMILTON: Ann told me that when her daughter was three months old, she started to have epileptic seizures. And for Mora, what that meant was, you know, her eyes would roll back, and she would pretty much lose awareness of what was going on around her.

BARBER: That must have been terrifying for her mother.

HAMILTON: It was. And it was even more terrifying because these seizures kept getting worse.

LEEB: These seizures started to cluster, and there were 20 of them in a minute. And then there were hundreds of them a day.

HAMILTON: Doctors, at this point, realize there's something going on. So they order an MRI of her brain. And Ann told me that when they had done that, they showed the image to her and her husband, Seth.

LEEB: Seth and I have no background in medicine, but you just didn't need it to read that MRI. Half of her brain was lit up, and the other half her brain was basically gray.

BARBER: So what does this mean?

HAMILTON: Most of the cells were damaged or dead, and the cells that were still there were causing these seizures. So the only thing surgeons really had to offer was that they would remove the left side of Mora's brain, including areas that were still controlling movement on one side of her body.

LEEB: Basically, the surgery created a newborn. She could no longer roll over. She could no longer smile. It was almost like a restart.

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HAMILTON: The left side of your brain is really important to speech and language. That's the side where those functions usually reside, at least for the most part. So with Mora, one of the big questions was, would she ever be able to speak?

BARBER: Today on the show, what happens when an infant loses half their brain.

HAMILTON: And why the findings have really surprised a lot of researchers.

BARBER: I'm Regina Barber.

HAMILTON: I'm Jon Hamilton.

BARBER: You're listening to SHORT WAVE from NPR.

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BARBER: OK, Jon, that was really heavy, the story of Mora's infancy. Can we start off with what I hope is a little relief about how Mora has grown up since?

HAMILTON: Yeah. I mean, she's a real success story, but her life started out pretty rough. And for her parents, you know, they did the only thing you could really do after she had the surgery, which is they got really extensive physical therapy, cognitive therapy, all that stuff. And eventually, over time, Mora did start to reach milestones but late. So for instance, when she was 18 months old, she finally sat up. And this is something most kids do when they're about 9 months old. When Mora was 23 months old, she started walking. Most kids do that, you know, somewhere between nine months and 17 months. And when Mora was 6 1/2 - and this is really late - she began using sentences. Most kids will start to use full sentences sometime between 2 and 3.

BARBER: Wow. I mean, how much of her ability to learn all these tasks were just because she was an infant and her brain was actually still forming?

HAMILTON: If she had not been an infant, this surgery probably would have been just devastating. And the reason is that really early in life, the wiring in your brain is still kind of this work in progress. So for instance, adults, when they process words, that takes place on the left side of the brain, usually. When they process faces and recognize faces, that happens on the right side of the brain. But in a kid, all that wiring is a lot looser. And I talked with Michael Granovetter about this. He's a researcher at the University of Pittsburgh.

MICHAEL GRANOVETTER: Your brain doesn't start out having word recognition completely on the left and face recognition completely on the right.

HAMILTON: Michael says that those two functions actually compete for space at first. And eventually, the brain kind of pushes them to opposite sides so they each have enough room.

BARBER: So if that's the case normally, what happens with somebody like Mora, like, who loses half her brain before these functions start to push each other to competing sides?

HAMILTON: Doctors really don't know a lot about - I mean, there's a limited number of these kids. And there haven't been a lot of, like, scientific studies charting the progress of all of them. So doctors really didn't know what to say. There were a lot of questions.

GRANOVETTER: If this competition between word recognition and face recognition in the brain plays out over development, what if only one hemisphere was available? What might we see? Can one hemisphere actually take on the burden of two?

BARBER: So how do doctors help? How do they provide reassurances to parents when they don't know the scope? Like, what can they honestly give as a reassurance?

HAMILTON: What they can give is this sort of anecdotal evidence that some kids get remarkably better, but some kids don't. And it depends in part on the age of - which this happens. It depends on the rehabilitation, all those kinds of things. So as part of an effort to find out more, Michael and a team, they studied face and word recognition in 40 people, including Mora.

BARBER: And had all 40 people lost half of their brain as a kid?

HAMILTON: Yes. Some of them were older. Some of them were about the same age as Mora. What the researchers were really concerned about was they knew that for grown-ups, if you had a stroke on the left side of your brain, it permanently affects skills like reading. I talked to Marlene Behrmann, who's a professor of psychology at Carnegie Mellon University. She is an expert on what is known as visual cognition. So that's how your brain processes what you see. And this is what she said about strokes in adults.

MARLENE BEHRMANN: Even if it is really a focal and circumscribed injury, they will be profoundly impaired at word recognition.

HAMILTON: So the big question for Mora was, would that be true for her?

BARBER: So is it, Jon?

HAMILTON: Well, let me let me get you the answer that I got from Marlene Behrmann.

BEHRMANN: Much to our surprise, we found that that's absolutely not true. Irrespective of whether the left or the right hemisphere is preserved, these kids can recognize both faces and words.

HAMILTON: And so for Mora, that meant that her brain had taken over executing all those tasks.

BARBER: Oh, that's a relief.

HAMILTON: It is. And I should point out here that we're talking about 80% accuracy in these kids. Kids with typical brains will do greater than 90%. So there is some impairment. It's significant. But it's far less than with brain injuries you see that happen later in life.

BARBER: So what is this 80% accuracy look like for Mora and these other kids?

HAMILTON: I asked Dr. Lisa Shulman about that. She's a neurodevelopmental pediatrician at Montefiore in New York. And what she told me is that there are some limits, but they're not that severe. Here's what she said.

LISA SHULMAN: When you lose that left side, which is controlling a lot of motor functioning, it can impact the mouth, the tongue, the palate, how all those things come into play.

HAMILTON: And you can hear that when you talk to Mora. But Lisa also told me that this girl has made amazing progress.

SHULMAN: Every time I see her, she's done something I could not have imagined when I first met her.

BARBER: Can you give me some examples of what this doctor is being surprised by?

HAMILTON: When I talked to Mora, I got a sense of this because, even though she has trouble speaking sometimes, and sometimes she has trouble processing language that she hears, she has this amazing sort of high-level understanding of certain language concepts like...

MORA: Idioms.

HAMILTON: Do you have a favorite idiom?

MORA: Going through and rose-colored glasses.

HAMILTON: So she gets something that is a fairly sophisticated linguistic concept, but some of the other things she has trouble with. So let me give you an example. You know, she loves to tell jokes, right? But sometimes she can be kind of thrown...

BARBER: OK.

HAMILTON: ...If there's, like, an unfamiliar concept or a joke has a sneaky punchline.

MORA: So can you tell me a joke?

HAMILTON: OK. I'll tell you a joke. So a termite walks into a bar and says, where is the bartender?

BARBER: Jon, that's not Mora. I don't get that joke.

HAMILTON: It's a science nerd joke. You have to know that termites like to munch on softer wood, OK?

BARBER: It's a terrible joke (laughter).

HAMILTON: Get over it. I mean, Ann Leeb got over it. Well, actually, no, she didn't.

LEEB: OK. That didn't go over so well, Jon (laughter).

HAMILTON: I know, I know. But I'm not the one who's good at telling jokes here.

BARBER: Yeah. You got to leave it to Mora.

HAMILTON: Yeah, yeah, yeah, yeah. Lesson learned, Gina. But, you know, that terrible joke actually serves a point because it shows how Mora has difficulty processing certain things on the fly. Like, it's not just that it was a lousy joke, but she was trying to figure out what the whole concept...

BARBER: Right.

HAMILTON: ...I was presenting here, right? And there are some other challenges, including some things that won't go away. The right side of her body will never be as strong as the left side. And she also has, like, a visual deficit. She will never see things that are to the right of her nose. She gets, like, a half view of the world.

BARBER: Wow.

HAMILTON: But in a lot of other areas, I mean, Mora's brain is still learning and rewiring and adapting. I mean, her social skills are improving. And she has this personality that everybody says is - continues to emerge.

BARBER: So is this changing how neuroscientists and doctors are thinking about how the brain can rewire themselves after an injury, like, being plastic?

HAMILTON: Oh, definitely. I mean, they are seeing things here that show these extreme examples of plasticity, things that doctors really didn't think were possible. So that gives them hope. It gives parents hope. And I know it gave Ann Leeb hope because here's what she says about her daughter.

LEEB: She's met so many expectations and gone beyond. Check in with us, Jon, in five years, and we'll be telling you more.

BARBER: I hope you do check in in five years.

HAMILTON: I do, too, because I am really confident that, a few years from now, Mora will be doing things that she's not doing now. She will have reached a different level, and that would be fun to see.

BARBER: OK, Jon, I'm definitely looking forward to you coming back on the pod and giving us an update on Mora.

HAMILTON: Anytime.

BARBER: This episode was produced by Brit Hanson, edited by managing producer Rebecca Ramirez and fact-checked by Jon Hamilton. The audio engineer for this episode was Stacey Abbott. Special thanks to Amina Khan. Beth Donovan is our senior director. And Anya Grundmann is our senior vice president of programming. I'm Regina Barber. Thanks, as always, for listening to SHORT WAVE from NPR.

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