Dr. Mercola writes about Harvard fluoride study

Six Facts You Need to Know About Water Fluoridation

Reported effects of fluoride on your brain include:

Reduction in nicotinic acetylcholine receptors	Damage to your hippocampus	Formation of beta-amyloid plaques (the classic brain abnormality in Alzheimer's disease)
Reduction in lipid content	Damage to purkinje cells	Exacerbation of lesions induced by iodine deficiency
Impaired antioxidant defense systems	Increased uptake of aluminum	Accumulation of fluoride in your pineal gland

http://articles.mercola.com/sites/articles/archive/2012/08/14/fluoride-effects-in-children.aspx?e_cid=20120814_oldPRNL_art_1