Chapter 33 Diseases of the Nervous System
The nervous system of the bird is arranged similar to that of mammals with some major differences. The neocortex, developed on the surface of the cerebral cortex of mammals, is not superficial in birds; cortical cells are found deep within the cortex. Also, birds have the ability to repopulate neurons and reestablish tracts within the central nervous system. The cranial nerves are similar to those in mammals. Birds are intelligent and can outperform mammals in many problem-solving experiments. Studies using Alex (Alex belongs to Dr. Irene Pepperberg, Department of Psychology, Brandeis University. He is being used to study the cognitive and learning abilities of birds as related to great apes and other animals), an African gray parrot, showed avian intelligence levels close to that of a 4-year-old child. Birds have highly developed color vision, good hearing, and the ability to vocalize. Vocalization may be inherited, learned, or invented. Anyone who has owned one of the talented breeds of talkers has heard their vocal ability! Vocalization is used by the bird to attract other birds, to gain attention of the owner, for song, and for amusement.
Neurologic disease is common in pet birds; however, diagnosis is more difficult than in mammals because most of the tests used in mammals are not applicable to avian species. As in other animals, the age of the animal may provide a list of rule-out diseases (e.g., epilepsy in younger birds, neoplasia in older ones).
Seizures are defined as paroxysmal, uncontrolled, electrical discharges from the brain. They may be mild to severe, generalized or partial, frequent or infrequent. Seizures may progress as in mammalian patients with a variable postictal period. During the seizure birds may fall off their perch, loose consciousness, become rigid, or have excessive motor activity.