As the baby boom generation grows older, understanding the specific physiological changes in aging humans will be key in developing new treatments for age-related disorders. With advancing age, verbal knowledge remains stable, but short-term memory, working memory, mental processing speed and long-term memory decrease. Yerkes researchers are studying older nonhuman primates to define the normal course of aging and to establish how aging influences the development of neurodegenerative diseases. Drawing on neuroimaging, behavioral testing and neurohistological analyses, researchers are trying to determine why neurodegenerative diseases, such as Alzheimer’s disease, appear to be unique to humans. These studies will give insight into the biological basis of age-related functional decline and into the factors that can influence healthy aging.