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The diesase is characterized by the gradual spread of sticky plaques and clupms of tangles fibers that disrupt the delicate organization of nerve cells in the brain. As brain cells stop communicating with one another, they atrophy - causing memory and reasoning to fade.
Tangles and plaques first develop in the entorhinal cortex, a memory-processing center essential for making new memories and retrieving old ones.
Over time, they appear higher, invading the hipppocampus, the part of the brain that forms complex memories of events or objects.
Finally the tangles and plaques reach the top of the brain, or neocortex, the "executive" region that sorts through stimuli and orchestrates all behavior.
A brain ravaged by Alzheimer's shrinks in size and weight as the disease destroys neural tissue. The once tightly packed ruts and grooves on the surface of a healthy cerebral cortex become visibly pitted with gaps and crevices.
