The Earth's population is aging fast, and the coming sharp increase in the number of people over age sixty-five will bring with it an epidemic of age-related neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Currently, no cures exist for the major neurologic disorders. Unless cures can be found, by 2050 the cost of these diseases will exceed $1 trillion annually in the United States, and the burden for other countries will scale with their populations. Despite exciting advances in our understanding of these diseases, both government research funding and the efforts of industry have failed to keep pace with this unmet medical need. Private philanthropy has done better, but the total dollars spent on developing diagnostics and therapeutics for neurologic disorders still lags far behind that spent on much less prevalent diseases. The challenge for biomedical research in the next forty years is to identify markers that would allow early detection of high-risk cohorts, and to develop therapies that either will prevent the diseases from starting at all in susceptible populations or will arrest their progression before severe damage to the central nervous system has occurred.