Alzheimer disease, which occurs in approximately 5 percent of the population above the age of sixty-five. It is characterized by progressive loss of memory and other mental functions. At first, the person may have difficulty remenbering appointments and sometimes fails to think of words or people's names. As time passes, he or she shows increasing confusion and increasing difficulty with tasks such as balancing a checkbook. In the early stages, the memory deficit involves recent events; but as the disease progresses, even old memories are affected. If the person ventures outside alone, he or she os likely to get lost. Eventually, the person becomes bedridden, completely helpless, and, finally, succumbs.

Alzheimer disease produces severe degeneration of the hippocampus and cerebral cortex, especially the association cortex of the frontal and temporal lobes. Figure a abd b show photographs of the brain of a patient with Alzheimer disease and of a normal brain. It shows how much wider the sulci are in the damage brain, especially in the frontal and temporal lobes, indicating substantial loss of cortical tissue.

 (a)  Normal
(b)  Alzheimer disease (AD)