Neuropsychological tests are used to examine brain function and impairment. The Luria-Nebraska and Halstead-Reitan test batteries are the best known and most commonly used neuropsychological measures. By using such measures, neuropsychologists can detect and localize organic brain impairment, and develop rehabilitation programs for cognitively impaired individuals. A neuropsychologic evaluation is more sensitive to the functional manifestations of brain impairment than neurological tests, such as an MRI or CAT scan.