Postnatal Cochlear Ca2+ Activity and Synaptic Innervation Relative to Frequency-Based Regions

Hearing is an essential function to humans as it strongly contributes to their survival and quality of life. In order to hear, sound must enter the cochlea (the inner ear) via vibrations through the oval window located at its base (region reserved for high frequencies), activating hair cells throughout the spiral at other various regions. Since the sound wave first enters the cochlea at the base (more frequent activation throughout lifetime), a higher degree of calcium (Ca2+) activity and a higher degree of innervation during development by the hair cells at the base of the cochlea is hypothesized as an enhanced effort for the preservation of hair cells located at base. Although the results between the regions support the theory of a higher degree of Ca2+ activity at the base of natural cochlea, it does not support the theory of synaptic innervation being influenced by cochlear region.