Inferior colliculus

The inferior colliculus (IC) (Latin for lower hill) is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex. The inferior colliculus has three subdivisions: the central nucleus, a dorsal cortex by which it is surrounded, and an external cortex which is located laterally. Its bimodal neurons are implicated in auditory-somatosensory interaction, receiving projections from somatosensory nuclei. This multisensory integration may underlie a filtering of self-effected sounds from vocalization, chewing, or respiration activities. The inferior colliculi are part of the tectum of the midbrain, and together with the superior colliculi form the corpora quadrigemina. An inferior colliculus lies caudal/inferior to the ipsilateral superior colliculus, rostral/superior to the superior cerebellar peduncle and the trochlear nerve, and at the base of the projection of the medial geniculate nucleus and the lateral geniculate nucleus. The inferior colliculus has three subdivisions – the central nucleus, the dorsal cortex by which it is surrounded, and an external cortex which is located laterally. The inferior colliculi of the midbrain are located just below the visual processing centers known as the superior colliculi. The inferior colliculus is the first place where vertically orienting data from the fusiform cells in the dorsal cochlear nucleus can finally synapse with horizontally orienting data. Sound location data thus becomes fully integrated by the inferior colliculus. IC are large auditory nuclei on the right and left sides of the midbrain. Of the three subdivisions the central nucleus of IC (CNIC) is the principal way station for ascending auditory information in the IC. The input connections to the inferior colliculus are composed of many brainstem nuclei. All nuclei except the contralateral ventral nucleus of the lateral lemniscus send projections to the central nucleus (CNIC) bilaterally.