This video shows better than any other discussion I've seen why mercury is linked to Alzheimer's Disease. The hallmark histologic finding of AD is neurofibrillary tangles. Nerves that clump together and form a wad of nerves rather than connecting the brain together in a systematic fashion. Tubulin is the insulation for nerves. Adding tiny amounts of mercury cause the insulation to fall off the nerve and they then knot up just like is found at autopsy in AD.