9408170 Brown ABSTRACT The long-term objectives of this project are to understand how new brain cells can be added to adult brains. In mammals including humans, brain cells called neurons are created only during very early development, and neurons that are lost as a result of injury or disease cannot be replaced. Using an animal model in which neurons are added to already-existing brain circuits which are important for learning and producing sounds used to communicate, anatomical and behavioral studies will address the biological events that promote the addition of new neurons to the brain. Understanding how neurons may be added to the brain could lead to therapies which would ameliorate the devastating effects of neurological disease.