What is the difference between the brain of someone with alzheimer's and a normal brain?

Alzheimer: Brain shows loss of neurons & synapses, leading to atrophy in affected areas of the brain.

Many differences: There are a number of classic changes found in the brains of someone with Alzheimer's disease. There is a generalized wasting of the brain which can be see on CT Scan. Microscopic examination of autopsied brains, show that many neurons (brain cells) are disarrayed, forming tangles; and there are plagues made of a substance called amyloid. There are also chemical differences, eg. low acetylcholine