"The cerebellum is like a really fast math-coprocessor for the brain. It can take in multiple channels of input (vestibular, auditory, occular, signals from other parts of the brain), and anything that the brain has learned previously, it can "automate" it, including the retrieval of information responsible not only for motor movement, but for cognition and memory as well. Anyway, exercises are just designed to challenge the cerebellum's ability to perform different combinations of these functions at the same time so it grows and gets more efficient. "