Figure 3.

Diagram depicting the innervation inner (IHCs) and outer hair cells (OHCs) by spiral ganglion neurons (SGNs) in the adult cochlea. Illustration of the mature pattern of cochlear afferent innervation. Mature IHCs are innervated by ∼95% of the type I SGN fibers. In mice, about 10–20 unbranched myelinated SGNs connect with a single IHC while each neuron receives input from only one IHC. The remaining ∼5% of SGNs are type II unmyelinated neurons that project toward the OHCs and spiral toward the base of the cochlea contacting multiple OHCs.