Fig. 5.

Summary diagram illustrating tonotopic organization in the mammalian cochlea. (A) The tonotopic organization of the cochlea is established sequentially. First, apical-to-basal regional identity is established. This then provides a framework upon which the basal-to-apical tonotopic characteristics tuned to specific frequencies appear along the mature cochlea. (B–D) Loss or gain of FST or SHH function perturbs this framework in the developing cochlea, resulting in changes in the tonotopic characteristics of the mature cochlea. See the Discussion section for details on each genotype.