What does the cerebellum do?

The cerebellum is the portion of the brain that controls coordination, balance, voluntary motor movements, sense of position of the different parts of your body, equilibrium, and muscle tone.

The cerebellum modulates voluntary movement commands so that the movements become progressively more accurate, smoother, and require less conscious effort to perform. For example, when learning to ride a bike you have to consciously balance, coordinate your arms and legs, and direct yourself using your eyes. As you practice, and the cerebellum becomes more accustomed to the demands of the task, you can eventually do the task without thinking (indeed, with eyes closed!).

We know that the cerebellum does this (modulating, rather than initiating movements) because patients with damage to the cerebellum have coordination problems, but can still move.

There are increasing reports that the cerebellum is important for other, non-motor, tasks. Tasks that require forward-planning seem to involve the cerebellum. It is becoming more clear that the cerebellum has a wider-reaching role in fine-tuning a variety of neural signals.