Cochlear nucleus

Cochlear nuclei
Dissection of brainstem. Dorsal view. ("Cochlear nucleus" is labeled on left, fifth from the bottom.)
Terminal nuclei of the cochlear nerve, with their upper connections. (Schematic.) The vestibular nerve with its terminal nuclei and their efferent fibers have been suppressed. On the other hand, in order not to obscure the trapezoid body, the efferent fibers of the terminal nuclei on the right side have been resected in a considerable portion of their extent. The trapezoid body, therefore, shows only one-half of its fibers, viz., those that come from the left. Vestibular nerve, divided at its entrance into the medulla oblongata Cochlear nerve Accessory nucleus of acoustic nerve Tuberculum acusticum Efferent fibers of accessory nucleus Efferent fibers of tuberculum acusticum, forming the striae medullares, with 6’, their direct bundle going to the superior olivary nucleus of the same side; 6’’, their decussating bundles going to the superior olivary nucleus of the opposite side Superior olivary nucleus Trapezoid body Trapezoid nucleus Central acoustic tract (lateral lemniscus) Raphé Pyramidal tracts Fourth ventricle Inferior peduncle
Details
Part of	brainstem
System	Auditory system
Artery	AICA
Identifiers
Latin	nuclei cochleares
NeuroNames	hier-717
NeuroLex ID	Cochlear nuclear complex
Dorlands /Elsevier	n_11/12580764
TA	A14.1.04.247 A14.1.05.430
FMA	72240
Anatomical terms of neuroanatomy []

The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN). The ventral cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered. Auditory nerve fibers, fibers that travel through the auditory nerve (also known as the cochlear nerve or eighth cranial nerve) carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus. At the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus. All acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins. The outputs from the cochlear nuclei are received in higher regions of the auditory brainstem.

The cochlear nuclei (CN) are located at the dorso-lateral side of the brainstem, spanning the junction of the pons and medulla.

The major input to the cochlear nucleus is from the auditory nerve, a part of Cranial nerve VIII (the vestibulocochlear nerve). The auditory nerve fibers form a highly organized system of connections according to their peripheral innervation of the cochlea. Axons from the spiral ganglion cells of the lower frequencies innervate the ventrolateral portions of the ventral cochlear nucleus and lateral-ventral portions of the dorsal cochlear nucleus. The axons from the higher frequency organ of corti hair cells project to the dorsal portion of the ventral cochlear nucleus and the dorsal-medial portions of the dorsal cochlear nucleus. The mid frequency projections end up in between the two extremes; in this way the tonotopic organization that is established in the cochlea is preserved in the cochlear nuclei. This tonotopic organization is preserved because only a few inner hair cells synapse on the dendrites of a nerve cell in the spiral ganglion, and the axon from that nerve cell synapses on only a very few dendrites in the cochlear nucleus. In contrast with the VCN that receives all acoustic input from the auditory nerve, the DCN receives input not only from the auditory nerve but it also receives acoustic input from neurons in the VCN (T stellate cells). The DCN is therefore in a sense a second order sensory nucleus.