A major goal of neuroscience research is to develop effective treatments for clinical disorders, including those with underlying central nervous system (CNS) dysfunction. Progressive CNS diseases are characterized by the continuous deterioration of both cognitive and motor functions, leading to prolonged periods of increasing incapacity. Among the most problematic and prevalent neurological disorders are those associated with the loss of specific populations of brain neurons. Today, approx 12 million people in the United States suffer from such neurological disorders. Estimated costs in the United States of public expenditures and secondary medical expenses for treating patients with neurological disorders exceed $400 billion annually. Expenses directly attributed to organic neurological disease account for only about 25% of that amount. Beyond monetary costs to the health care economy, however, the medical, societal, familial, and personal costs cascading from these diseases defy calculation. Despite significant advances in technology and in understanding CNS disorders, effective treatments for progressive neurological disorders remain elusive.