Britannica Sources used in this answer

How does the cochlear nerve carry sound information to the brain?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Cross-section diagram of the human ear showing the outer ear, middle ear, and inner ear, with labeled parts including the auricle, auditory canal, tympanic membrane, ossicles, cochlea, semicircular canals, and nerves. — human ear Structure of the human ear.

The cochlear nerve carries sound information to the brain through a process of mechanical-to-electrical transduction and neural transmission.

Within the organ of Corti, sound vibrations cause the basilar membrane to move, creating shearing forces that bend the stereocilia of the hair cells. This bending opens ion channels, leading to the depolarization of the hair cells and the subsequent release of neurotransmitters at their base.1

These neurotransmitters stimulate the nerve endings of the cochlear nerve, which originate from the spiral ganglion in the modiolus of the cochlea. The axons of these bipolar neurons unite to form the cochlear nerve trunk. These primary auditory fibres exit the modiolus and travel to the medulla oblongata in the brainstem, where they deliver the electrical signals for further processing and analysis by the central auditory pathways.21

Pitch is coded by which specific neurons are responding, while loudness is determined by the total number of activated neurons and their rate of response.3