It's the part of the brain that makes sure you cannot tickle yourself. The cerebellum, an apple-sized region near the base of the skull, senses that your own fingers are the ones trying to tickle, and cancels your usual response.
Now an international team of researchers has learned something surprising about this region, which despite its small size contains roughly half of all the neurons in the brain. These neurons, which were thought to fire only rarely as they take in information from the senses, are in fact far more active than previously suspected.
The study underscores new theories about the role of the cerebellum, which is increasingly being viewed as involved in cognitive processes both in adulthood and in development. Read more about "Neurons and the cerebellum."