MKI67 and noise induced hearing loss: Compared with the findings in age-matched control mice, the densities of Ki67+ cells and DCX+ cells were clearly reduced in NIHL mice at 1 MPN and 3 MPN, while no significant differences between age-matched groups were shown at 4 DPN and after 6 MPN, suggesting that NIHL accelerates the age-related decline in neurogenesis.