Effect of near-infrared light treatment on hyperphosphorylated tau and neurofibrillary tangles in the hippocampus of K3 mice. (A), (B) Quantification of tau AT8 immunolabelling, based on average labelling intensity (A) and labelled area (B). All error bars indicate standard error of mean. **P < 0.01, ***P < 0.001. (C), (D), (E) Representative photomicrographs of sections of the hippocampal subiculum area, stained with Bielschowsky silver stain to demonstrate neurofibrillary tangles (NFTs). Arrows indicate axonal swellings and NFTs. The classical silver stain also labelled axons in the white matter core (WM). (F), (G), (H) Representative micrographs of AT8 (red) labelling within hippocampal CA1 pyramidal neurons. Nuclei were labelled with bisbenzimide (blue). Scale bars = 50 μm; scale in (E) applies to (C) and (D), scale in (H) applies to (F) and (G). NIr, near-infrared light; WT, wildtype.