What is ? The most common form of dementing illness, (AD) is a progressive, degenerative disease that attacks the brain, causing impaired memory, thinking and behavior. The person with AD may experience confusion, personality and behavior changes, impaired judgment, and difficulty finding words, finishing thoughts or following directions. It eventually leaves its victims incapable of caring for themselves. What happens to the brain in Alzheimers Disease? In AD The nerve cells in the part of the brain that controls memory, thinking, are damag ....