Each inner hair fiber has 16-20 associated auditory nerve fibers. 90-95% of the nerve fibers are edicated to the IHC.

Grinnell College

There are four types of nerve fibers and synapses. 
- efferent and afferent nerves
- glutamate, acetylcoline, GABA and dopamine

Auditory nerve fibers in the organ of Corti

Inner hair cells, IHCs, are closer to the central axis of the cochlea. There are about 3500 in a single row.

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.