MAPT and early-onset autosomal dominant Alzheimer disease: The locus ceruleus is involved early in Alzheimer disease [54] and people with Alzheimer disease have more inorganic mercury in their locus ceruleus than controls [20]; furthermore, hyperphosphorylated tau is often found in the human locus ceruleus [54], and mercury causes tau hyperphosphorylation [55] and aggregation [56].