Neurodegenerative diseases occur when nerve cells in the brain or peripheral nervous system lose function over time and ultimately die. Although treatments may help relieve some of the physical or mental symptoms associated with neurodegenerative diseases, there is currently no way to slow disease progression and no known cures. The risk of being affected by a neurodegenerative disease increases dramatically with age. Population-wide health improvements have increased lifespan which, along with a larger generation of aging Americans, means more people may be affected by neurodegenerative diseases in coming decades. This creates a critical need to improve our understanding of what causes neurodegenerative diseases and develop new approaches for treatment and prevention.