Alzheimer's disease is a progressive, degenerative disorder that attacks the brain's nerve cells, or neurons, resulting in loss of memory, thinking and language skills, and behavioral changes.  

These neurons, which produce the brain chemical, or neurotransmitter, acetylcholine, break connections with other nerve cells and ultimately die. For example, short-term memory fails when Alzheimer's disease first destroys nerve cells in the hippocampus, and language skills and judgment decline when neurons die in the cerebral cortex.  

Two types of abnormal lesions clog the brains of Alzheimer's sufferers: Beta-amyloid plaques-sticky clumps of protein fragments and cellular material that form outside and around neurons; and neurofibrillary tangles-insoluble twisted fibers composed largely of the protein, tau, that build up inside nerve cells. Although these structures are hallmarks of the disease, scientists are unclear whether they cause it or a byproduct of it.  

Alzheimer's disease is not a normal part of aging.  

Origin of the term Alzheimer's disease dates back to 1906 when Dr. Alois Alzheimer, a German physician presented a case history before a medical meeting of a 51-year-old female patient who suffered from a rare brain disorder. His autopsy of the patient's brain identified the plaques and tangles that today characterize Alzheimer's disease.