The plasticity of the brain defies belief…a woman born without a cerebellum and not diagnosed till age 24. Which means that even though the genes that would normally be involved in cerebellum development were missing (actually they were there, they were just unable to perform this set of tasks), other genes were able to use other parts of the brain to perform the cerebellum’s tasks. The brain is able to function the way a drummer lays down a complex web of polyrhythms. That is, a drummer has two feet and two hands, but is able to create varying patterns by combining elements of the same hands and foot pedals striking in different but simultaneous patterns. And the brain can use the same neurons in varying patterns by making varying combinations of neurons…a neuron firing can fire off other neurons simultaneously so one neuron can be part of various chains of neurons performing various functions. It’s insanely complex.
Interesting, there is a famous case of a woman, Elizabeth, missing most of her cerebellum and treated using the Feldenkrais method.