The Jaw as Auditory Organ: Evolutionary Homology, Tensor Tympani Coupling, and the Jaw's Contribution to Interaural Signal Discrimination

The mammalian jaw and ear share evolutionary origin: the malleus and incus derive from the articular and quadrate jaw bones. This homology is functionally live. CN V3 innervates both jaw muscles and the tensor tympani, making jaw state a direct controller of middle ear acoustic impedance. TMJ vibrations conduct through bone directly to the cochlea. Jaw position asymmetrically affects ear canal geometry and tensor tympani tone, modulating the interaural level difference (ILD) used for left-right sound localization.

D(xi_hearing) is a function of D(xi_jaw).