DAVID GREENE, HOST:
Today in Your Health we explore a medical mystery of sorts and find out what scientists are learning from a man who was born with part of his brain missing.
JONATHAN KELEHER: My name is Jonathan Keleher.
JON HAMILTON, BYLINE: And how old are you?
J. KELEHER: I'm 33.
GREENE: Jonathan Keleher is one of just a few people known to have lived their entire lives with no cerebellum. The cerebellum is part of the brain that helps us do things like balance on one foot or touch our nose with an index finger. But people like Jonathan are showing it also plays an important role in emotion, thinking and personality. NPR's Jon Hamilton reports.
J. KELEHER: Hey.
HAMILTON: I meet Jonathan at his parent's house in a suburb of Boston.
J. KELEHER: Why don't you come in?
HAMILTON: Hey guys.
The whole family is here and Jonathan is doing what he likes best - socializing.
J. KELEHER: Why read a book or why do anything when you can be social and talk to people? And, I mean, we're all in this world together.
HAMILTON: Jonathan lives on his own and has a job at a nonprofit group. And he is doing all this without a cerebellum, a structure that contains about half of all the neurons in a typical brain. Jonathan and his family gather in the living room to tell his story. His mother, Catherine Keleher, says early on her son's future looked pretty uncertain.
CATHERINE KELEHER: All his milestones were late - sitting up, walking, talking. But they still didn't know what it was.
HAMILTON: Jonathan's father, Richard Keleher, says that turned out to be a good thing.
RICHARD KELEHER: Not knowing what the diagnosis was, we said, well, let's assume he can do everything.
HAMILTON: So Jonathan got special education, speech therapy, physical therapy - his father even came up with a sort of beach therapy.
R. KELEHER: I took him to the beach every day because he wasn't walking. And I was freaking out because I have a handicapped sister. And so I was doing everything I could do. And I found that if I took him to the beach, he would try to walk.
HAMILTON: Jonathan was 5 when a brain scan finally revealed the problem. A few years after that, he was referred to Jeremy Schmahmann, a neurology professor at Harvard. An image of Jonathan's brain is on a computer screen the day I visit Schmahmann's lab. He points to an area just above the brainstem.
JEREMY SCHMAHMANN: So he has this remarkable black space down here, which is where the cerebellum is supposed to be.
HAMILTON: Well, it couldn't be any more obvious than that, could it?
SCHMAHMANN: There's a very big area of nothingness there.
HAMILTON: Schmahmann has been studying the cerebellum for more than 30 years. He says until recently, it was known only for its role in balance and fine motor control. You can learn a lot about that role by watching someone who's been pulled over for drunken driving.
SCHMAHMANN: The state trooper test is a test of cerebellar function. So the effect of alcohol on the cerebellar function is identified by everybody who's ever done walking a straight line or touching their finger to their nose.
HAMILTON: Of course, Schmahmann says, it's not exactly glamorous being the part of the brain that lets people pass a sobriety test.
SCHMAHMANN: I sometimes joke that the cerebellum is the Rodney Dangerfield of the brain - don't get no respect.
HAMILTON: But Schmahmann and others have spent decades building a case that the cerebellum does a lot more. First, they showed that it has connections to brain areas that perform higher functions, like using language, reading maps, and planning. Then, a few years ago, functional MRI studies began to suggest that the cerebellum was actively involved in these tasks.
SCHMAHMANN: The big surprise from functional imaging was that when you do these language tasks and spatial tasks and thinking tasks, lo and behold the cerebellum lit up.
HAMILTON: But Schmahmann says some of the most compelling evidence has come from people who do not have a cerebellum, people like Jonathan Keleher. Years of research on them supports the idea that the cerebellum has just one job. It takes clumsy actions or functions and makes them more refined.
SCHMAHMANN: So it doesn't make things. It makes things better.
HAMILTON: Schmahmann says that's pretty straightforward when it comes to movement. The brain's motor cortex tells your legs to start walking. The cerebellum keeps your stride smooth and steady and balanced.
SCHMAHMANN: What we now understand is that what the cerebellum is doing to movement, it's also doing to intellect and personality and emotional processing.
HAMILTON: It's making all those things better, too. Unless you don't have a cerebellum. Then, Schmahmann says, thinking and emotions can become clumsy. Richard Keleher says his son Jonathan got a reminder of this at a busy intersection soon after he got his driver's license.
R. KELEHER: The first day he drove, he had a bus behind him. He was anxious about holding the bus up.
HAMILTON: He totaled his father's car. Not because he lacked the physical coordination to drive, but because his brain couldn't coordinate all the information - the bus, the cars, the intentions of other drivers. Jonathan says he doesn't drive anymore because he can't react quickly enough.
J. KELEHER: Reaction time - not my strong suit.
HAMILTON: Neither is emotional complexity. Jonathan's sister, Sarah Napoline, says her brother is a great listener, but not introspective.
SARAH NAPOLINE: He doesn't really get into this deeper level of conversation that builds strong relationships, things that would be the foundation for a romantic relationship or deep, enduring friendships. It can be a little bit surface-level.
HAMILTON: When Jonathan hears this, he nods.
J. KELEHER: I agree. And yeah that's true, I tend not to.
HAMILTON: Sarah says her brother also has trouble reading people's intentions. She tells him that may have been why a recent relationship with a young woman never became romantic.
NAPOLINE: I wonder if it's maybe a matter of her not making a first move, you not making a first move, and also you not being able to interpret if she wanted a move to be made.
J. KELEHER: Well, I don't know what a move is.
J. KELEHER: I need to be taught this stuff, OK?
HAMILTON: Jonathan's right. He needed to be taught a lot of stuff that people with a cerebellum learn automatically - how to speak clearly, how to behave in social situations, how to show emotion. Schmahmann say Jonathan has been able to do all this by training other areas of his brain to do the jobs usually done by the cerebellum. Richard Keleher says it's taken decades. And he says it couldn't have happened at all if his son were less resilient and determined.
R. KELEHER: There were times when I realized how brave my son has been being out there on his own - this little kid in a car, going off to school by himself, and trying things, you know, going down to the beach and falling down again, and again, and again, and again. It's pretty impressive.
HAMILTON: Schmahmann says what he's learning from people like Jonathan could help hundreds of thousands of people whose cerebellums are damaged later in life by a stroke or an infection or disease. Jon Hamilton, NPR News.
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