New Study Details Cerebellum’s Role in Language Processing

For more than a century, scientists studying how the brain processes language have primarily focused on the cerebral cortex, a higher-order brain region that carries out complex cognitive tasks.

But there is another less well-studied collaborator in language processing: an evolutionarily ancient brain structure known as the cerebellum.

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Now, a team led by researchers at Harvard Medical School, Harvard University, and MIT is probing the details of the cerebellum’s contribution to language processing.

The scientists performed brain scans on human subjects engaged in language and nonlanguage tasks and found evidence that regions of the cerebellum are involved in language processing. Specifically, they identified four regions that responded to language in some way — including one that responded exclusively to language.

“When you put someone in a scanner and have them listen to a story or read a sentence, you consistently see the cerebellum light up,” said lead author Colton Casto, a Harvard Kenneth C. Griffin Graduate School of Arts and Sciences doctoral student in the Speech and Hearing Bioscience and Technology (SHBT) program at HMS.

The research provides new insights into how regions of the cerebellum process language — and suggest that this processing may happen differently than language processing in the cerebral cortex.

Casto sees the work as part of a broader effort to chart the brain’s extended language network — the brain areas outside the cerebral cortex that are recruited for language processing.

The findings could also have implications for treating aphasia or other language disorders, Casto said, by providing another area of the brain to target.

The findings were published Jan. 22 in Neuron.

Unraveling language processing in the cerebellum

Previous studies have reported that the cerebellum, which is most well-known for coordinating the body’s movements, is also involved in language. However, scientists still don’t know whether the cerebellum contains regions dedicated solely to linguistic processes and how these processes work.

To address this gap, a team led by senior author Evelina Fedorenko, associate professor at MIT and a faculty member in HMS’ SHBT program, set out to systemically characterize the regions of the cerebellum that respond to language. The team asked a basic question: What do these regions contribute to language processing?

The researchers used functional magnetic resonance imaging (fMRI) to examine brain activity in more than 800 human participants performing 26 different tasks, including reading, listening, speaking, solving math problems, completing memory exercises, and processing visual stimuli. They then compared how different regions of the cerebellum responded to linguistic and nonlinguistic demands.

Importantly, the team localized language-responsive regions within each participant’s cerebellum before examining how those individualized regions responded across tasks. This individual-level analysis provided a clearer picture of the cerebellum’s involvement in language than previous studies that averaged brain activity across many participants.