A 24-year-old woman has been found to be missing her entire cerebellum, a brain structure that contains roughly half of the brain's neurons, yet she leads a normal life. She graduated from school, married, and gave birth after an uneventful pregnancy. The case, reported earlier this year, challenges fundamental assumptions about brain function.
The woman experiences mild motor difficulties, such as clumsy movements, but the absence of such a crucial region—present even in the earliest vertebrates—is remarkable. Scientists admit that the case highlights significant gaps in basic understanding of the brain, including the exact role of the cerebellum, which is typically associated with coordinating precise movements.
This resilience is partly due to the brain's plasticity, but also to a concept called 'degeneracy', proposed by Nobel laureate Gerald Edelman. Degeneracy means that multiple brain structures can support the same function, so if one region is damaged, others can compensate. This contrasts with human technology, where a single component often has a dedicated role.
Another recent case involved a man with a tapeworm that burrowed through his brain over four years, causing seizures and memory issues, yet he survived. Such examples show that the brain does not operate like a machine with a one-to-one mapping of structure to function. Instead, functions are distributed across multiple regions, making the brain remarkably robust.
