You would think that if a substantial part of your brain were missing, you would know. But when a 24-year-old Chinese woman went to the hospital seeking treatment for dizziness late last year, she learned for the first time that her cerebellum was simply not there.
Often referred to as the “little brain,” the cerebellum is a small, wrinkly structure that looks like a separate piece added on to the base of the brain. It contains half the neurons in the brain, takes up 10% of its total volume, and plays an important role in the coordination of smooth movement. Drunk people have movement difficulties because alcohol diminishes the functionality of the cerebellum. Diseases that lesion the area can cause serious issues, including lack of coordination in the limbs, problems with gait, and an inability to stand up voluntarily. People with cerebellar damage often have difficulties with speech and language as well. Given that even minor damage to the cerebellum usually causes very conspicuous effects in people, it seems safe to assume that the absence of the entire cerebellum would have obvious and devastating effects.
However, the woman without a cerebellum could walk and talk with only mild problems. She is reported to have started speaking comprehensively at age six and walking at age seven. The most evident symptoms she has are difficulty balancing and slurred speech. Therefore, her doctors were understandably astonished to find in her brain scans that she lacked a cerebellum.
This remarkable case is further evidence of the extraordinary plasticity of the brain. Because the woman was born without a cerebellum, the rest of her brain compensated for the missing piece. She might actually have had more evident motor control problems had she injured her cerebellum later on in life. But because she had no cerebellum to begin with, she had to learn from day one how to stand up and walk and talk without one.
It is highly likely that other areas of the brain’s cortex adopted some of the cerebellum’s usual functions. This kind of brain plasticity is not unheard of. For example, the Broca’s and Wernicke’s areas are two parts of the brain’s left hemisphere that are heavily involved in language processing. In patients who were born with damage to this area, similar areas in the right hemisphere are activated when processing language. It is thought that brain plasticity allows for areas in the right hemisphere to take up the role of processing language.
In the same way, it is possible that the woman’s experiences induced changes in neural connections and allowed areas of the cortex to adopt some of the cerebellum’s functions. The story of this woman’s life tells us that, just as people can learn to live without arms or legs, the brain can survive without some of its components.
Yuki Hayashi is a sophomore in Ezra Stiles College. Contact her at firstname.lastname@example.org.
(Featured image from here.)