A nerve filament which, contacting the base of hair cells in the organ of Corti (the hearing organ of the inner ear and contains receptors which respond to sound waves), then take a spiral course along the basilar membrane before entering the spinal ganglion.

The basilar membrane is a thin layer of tissue which is covered with mesothelial (flattened cells) which separates the cochlea from the scala (canals) tympani in the ear.

The cochlea is that part of the internal ear which is concerned with hearing.