Gene delivery techniques currently being used to deliver neurotrophin to various sites in the nervous system. Direct viral gene delivery of neurotrophin (NT) gene occurs through insertion of the neurotrophin into a viral vector and then placement of the viral vector into a host virus, such as adeno-associated virus or lentivirus. Virus is then directly injected into the brain area(s) through surgical techniques. Cell transfer gene delivery first involves obtaining host cells, preferably from the subject and then transfecting them with virus containing the neurotrophin gene. Once selection and amplification of genetically modified cells is performed, and production of the neurotrophin is confirmed, those cells are then injected or grafted into the brain area(s) through similar surgical techniques.