Spreading from the bottom to the top

The disease is characterized by the gradual spread of plaques and clumps of tangled 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 reason to fade.

1. Tangles and plaques first develop in the entorhinal cortex, a memory-processing center essential for making new memories and retrieving old ones.

2. Over time, they appear higher, invading the hippocampus, the part of the brain that forms complex memories of events or objects.

3. Finally, the tangles and plaques reach the top of the brain, or neocortex, the "executive" region that sorts through stimuli and orchestrates all behavior.

Gray Matters

A brain ravaged by Alzheimer's (right) shrinks in size and weight as the disease destroys neural tissue. The once tightly packed rut and grooves on the surface of a healthy cerebral cortex (left) become visibly pitted with gaps and crevices.

*Reprinted from TIME