A man’s incomplete brain reveals cerebellum’s role in thought and emotion

Since his birth 33 years ago, Jonathan Keleher has been living without a cerebellum, a structure that usually contains about half the brain’s neurons. This exceedingly rare condition has left Jonathan with a distinctive way of speaking and a walk that is slightly awkward.

He also lacks the balance to ride a bicycle. But all that hasn’t kept him from living on his own, holding down an office job and charming pretty much every person he meets. “I’ve always been more into people than anything else,” Jonathan tells me when I meet him at his parents’ house in Concord, Mass., a suburb of Boston.

“Why read a book or why do anything when you can be social and talk to people?” Jonathan is also making an important contribution to neuroscience. By allowing scientists to study him and his brain, he is helping to change some long-held misconceptions about what the cerebellum does.

And that, in turn, could help the hundreds of thousands of people whose cerebellums have been damaged by a stroke, infection or disease. For decades, the cerebellum has been the “Rodney Dangerfield of the brain,” says Dr. Jeremy Schmahmann, a professor of neurology at Harvard and Massachusetts General Hospital.

It gets no respect because most scientists only know about 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 says.

“The state trooper test is a test of cerebellar function. So the effect of alcohol on cerebellar function is identified by everybody who’s ever done walking a straight line or touching their finger to the nose.” But Schmahmann and a small group of other scientists have spent decades building a case that the cerebellum does a lot more than let people pass a sobriety test.

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, researchers began to do functional MRI studies that suggested that the cerebellum was actively involved in these tasks.

“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,” Schmahmann says. Some of the most compelling evidence, though, has come from research on a handful of people who have no cerebellum, people like Jonathan Keleher.

For the first few years, his future looked highly uncertain, says his mother, Catherine. “All his milestones were late: sitting up, walking, talking.” But during that time doctors and developmental health experts still didn’t know why Jonathan was having so much trouble. And that turned out to be a good thing, says his father, Richard.

“Not knowing what the diagnosis was we said, ‘Well, let’s assume he can do everything,’ “ he says. Keleher leaves a reminder note on his desk at the Institute for Community Inclusion, where he works. So Jonathan got special education, speech therapy and physical therapy. His father even came up with a sort of beach therapy.

“He wasn’t walking,” Richard says. “And I found that if I took him to the beach, he would try to walk.” Jonathan was five when a brain scan finally revealed the problem. And eventually he was referred to Schmahmann, who has spent his entire career studying the cerebellum.