Some well-known age-related neurological diseases include Parkinson's disease, Alzheimer's disease, deafness, and blindness. Even more common are the problems of aging which are not due to disease but to more subtle impairments in neurobiological systems, including impairments in vision, memory loss, muscle weakening, and loss of reproductive functions, changes in body weight, and sleeplessness. As the average age of our society increases, diseases of aging continue to become more common, and conditions associated with aging need more attention by doctors and researchers. In 1991, patients...