Cerebellum is the Latin term for "little brain". Since its discovery it has been known as the brain region responsible for balance and coordination. This description is true to some extent, but the cerebellum is responsible for much more. Contrary to what the name suggests, the cerebellum actually contains more neurons than all the rest of the brain.

The cerebellum is responsible for rapid movements that have specific timing, like tapping a rhythm on a table or playing a musical instrument. But also, most sports can only be performed when the cerebellum is intact.

There are several tests that can be performed to see if the cerebellum is functioning properly. These tasks are also often used to check if someone has had too much to drink. (That is because the cerebellum is affected by alcohol first.) The best-known of these tests is the finger-to-nose task. Here a person is asked to extend their arm and then touch the tip of their nose with their index finger. When the cerebellum is functioning properly, this movement occurs in three unconscious steps:

1. The finger moves quickly to a point just in front of the nose
2. For a very short time, the finger stays at the same point
3. The movement is completed slowly, and the finger comes to rest against the nose

Of the above steps, the first depends on the functioning of the cerebellum. This means that if the cerebellum does not function well, this step will not be completed properly. Thus, the person will either stop too early, when the finger is still far away from the nose, or too late, when the finger is already in the face.

The cerebellum is not only involved in movements. It also becomes active during sensory stimuli when no movement is involved. It all has to do with the timing of actions or stimuli. Someone who is good at tapping a rhythm (which relies entirely on timing) is also good at telling which stimulus is moving faster (this also relies on timing).

The cerebellum additionally plays a role in attention. It has been shown that for people with damage to the cerebellum it is more difficult to shift their attention, which creates problems when it is necessary to respond to a stimulus quickly.

Author: Myrthe Princen (translated by Melanie Smekal)

Image: Marcel Loeffen