The brain’s “little brain” may hold big promise for people with language trouble.
Tucked into the base of the brain, the fist-sized cerebellum is most known for its role in movement, posture and coordination. A new study maps the language system in this out-of-the-way place. These results, published January 22 in Neuron, uncover a spot in the cerebellum that shows strong and selective activity for language.
The new study is “excellent,” says neurologist and cerebellum researcher Jeremy Schmahmann of Massachusetts General Hospital and Harvard Medical School in Boston. His work and that of others have shown that the cerebellum contributes to language and thinking more generally. The new research scrutinized the cerebellum in detail, “confirming and extending previous observations and contributing to our understanding” of the cerebellum’s activity, he says.
Neuroscientist Colton Casto combed through about 15 years of brain scanning data collected by study coauthor Evelina Fedorenko, a cognitive neuroscientist at MIT, and her colleagues. Putting the data all together, the scans of 846 people showed brain activity in four spots in the right side of the cerebellum as people read or listened to a story.
Three of these spots were also active when people did other things, such as working out a math problem, or listening to music or watching a movie without words. But one spot was more discerning, says Casto, of MIT and Harvard University. This region didn’t respond to nonverbal movies or math. It also ignored orchestral or jazz music, which, like language, relies on syntax and patterns and sound. Instead, this spot is attuned specifically to words. “You have to be reading or listening to language to fully recruit this region,” Casto says.
These four spots varied a bit from person to person, the brain scans showed. Peaks of activity weren’t always in the same place. But generally, this cerebellum language system — all in the right side of the structure — mirrors aspects of the more well-known language systems in the left side of the neocortex, the wrinkly outer layer of the brain.
Fedorenko says that it is no longer surprising that parts of the cerebellum care about language. “The real value of Colton’s work lies in establishing that one of these cerebellar language areas is selective for language.”
The findings could nudge together two largely separate research fields, Fedorenko says. Cerebellum research mostly focuses on motor functions. And language research doesn’t generally focus on the cerebellum. Fedorenko hopes this new evidence “will help change both of these positions.”
A few caveats remain, Casto says. For one, it’s not clear whether the three regions that seem less selective for words are truly not that selective. A region that seems to respond to both math and language, for instance, might actually be two distinct, neighboring regions, each with specific tastes. The functional MRI scans might not be able to distinguish those smaller areas clearly.
It’s also not clear why this language system exists in the cerebellum at all. “It might do something different for language than what the neocortex does,” Casto says. “We haven’t figured out what that is.”
One idea that Casto is eager to explore is whether the cerebellum helps to shape the growth of more well-known language areas in the brain, perhaps early in life as language skills are developing. The researchers are also curious about the cerebellum’s behavior in polyglots, people who speak multiple languages.
These language regions in the cerebellum might have health implications, too. Language skills should be regularly checked after a cerebellum injury, for instance, Casto says. In fact, Schmahmann and his colleagues have described language deficits in people with cerebellum damage. And the cerebellum could turn out to be a useful brain spot to target for people with aphasia, a communication disorder that can leave people unable to speak, read or write.
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