Posterior cochlear nucleus

At a glance

English

Posterior cochlear nucleus

Latin (TA2)

Nucleus cochlearis posterior

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the posterior cochlear nucleus

The posterior (dorsal) cochlear nucleus is one of the two cochlear nuclei of the brainstem, the first relay stations of the hearing pathway. Every fibre of the cochlear nerve ends in these nuclei, so all sound information enters the brain through them. They sit on the dorsolateral surface of the brainstem where the pons meets the medulla. The anterior (ventral) nucleus lies in front, beside the inferior cerebellar peduncle; the posterior nucleus curves over it and wraps around the back of that peduncle, forming a small swelling on the floor of the lateral recess of the fourth ventricle known as the acoustic tubercle.

Unlike the anterior nucleus, the posterior nucleus is built in layers. Its outer molecular layer receives parallel fibres from granule cells, much as in the cerebellum, and carries signals about the position of the head and ears and from the somatosensory system. Its deep layer receives branches of cochlear nerve fibres and input from stellate cells of the anterior nucleus. The principal neurons, fusiform (pyramidal) cells and giant cells, gather both streams. Cochlear fibres end in an orderly way, low frequencies laterally and high frequencies medially, so the tonotopic map of the cochlea is kept.

Axons of the principal cells leave through the dorsal acoustic stria, cross the midline and join the lateral lemniscus of the opposite side to reach the inferior colliculus. The anterior nucleus, by contrast, sends its main output through the trapezoid body to the superior olivary complex. The posterior nucleus performs a spectral analysis of sound, picking out the notches made by the outer ear that tell whether a sound comes from above or below. By comparing these with the expected effects of head and ear movement it helps separate unexpected sounds from self-generated ones.

Tumours of the vestibulocochlear nerve sheath at the cerebellopontine angle can press on the cochlear nuclei. Electrodes of auditory brainstem implants, used when the cochlear nerves are missing or destroyed, are placed over the surface of the cochlear nuclei in the lateral recess.

Function and supply

Function

Receives cochlear nerve input from the ear of the same side and analyses the spectrum of sound, especially the cues used to locate a sound in elevation, before passing it to the opposite inferior colliculus.

Blood supply

Branches of the anterior inferior cerebellar artery, with a contribution from the posterior inferior cerebellar artery.