MAPT and early-onset autosomal dominant Alzheimer disease: We found that diffusible tau from Alzheimer’s disease or Pick’s disease patients’ brain aqueous extracts or the secretomes of trisomy of chromosome 21 induced pluripotent stem cell-derived neurons, like Alzheimer’s disease brain-derived amyloid-β and synthetic oligomeric amyloid-β, potently enhanced synaptic long-term depression in live rats.