Healthy and Alzheimer's neurons. Computer illustration comparing a healthy brain neuron (nerve cell, top) with one from a brain affected by Alzheimer's disease (bottom), showing the degeneration of microtubules (white) and the production of protein plaques (blue, bottom right). Alzheimer's is caused by neuron and synapse degeneration and the formation of protein plaques in the brain. This abnormal loss leads to atrophy (wasting) of the affected areas. Symptoms include memory loss, personality changes and confusion.