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. 2022 Feb 17;14:814528. doi: 10.3389/fnagi.2022.814528

Figure 2.

Figure 2

A loss of neurons with time reduces the ~ 28,000 SGNs in ~40-year-old humans to ~25% in 80-year-old humans (A, purple). A similar loss is shown for ~1,300 SGNs and reduces to ~40 in 18 month-old mice (A, green). Immunoreaction of labeling for neuron markers validates the inner ear afferents in control mice (B,B’). This is compared with Atoh-cre;Atoh1f/f ‘self-termination mice (C), Bronx waltzer (bv/bv) (D), Atoh-cre;Atoh1ki/f (E), and Pax2-cre;Neurod1 (F). Central projections reach the anterior (AVCN) and dorsal (DCN) cochlear compared to controls (G) and Atoh1 CKO mice (H) that show a tonotopic organization of SGN central projection, despite the absence of cochlear hair cells (H’)—modified after Nadol Jr (1990); White et al. (2000); Jahan et al. (2018); and Filova et al. (2020). Scale bars: 10 μm (B–F) and 100 μm (G–H).