A group of disorders marked by problems in the normal functioning of the brain. These problems can produce seizures, unusual body movements, a loss of consciousness or changes in consciousness, as well as mental problems or problems with the senses.

In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. Although the brain is usually cited as the supervisory center of vertebrate nervous systems, the same term can also be used for the invertebrate central nervous system. In most animals, the brain is located in the head.