Higher magnification images of silver (12 month-old) and Thioflavine-S (9month-old) stained cortices show mature tangles (white arrows in Thio-S stain) in rTg4510 and rTg4510-Mapt0/0 mice; enhanced pathological changes such as neuritic tau accumulation and neuropil vacuolation around NFTs are found only in rTg4510 mice. Stereological counting revealed similar numbers of cortical NFTs between in rTg4510 and rTg4510-Mapt0/0 mice at 9 and 12 month of age. Because of the pronounced neuronal death only in rTg4510 mice, the percentage of tangle-bearing neurons was ≈1.6 to 1.8-fold higher higher in 9 and 12-month old rTg4510 mice. Mean±SEM, n=3 sections/mouse, 3 mice/group. 