Individual differences |
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|Brain: Dorsal cochlear nucleus|
|Dorsal cochlear nucleus is #4, at upper left|
|Latin||nucleus cochlearis posterior|
The dorsal cochlear nucleus (DCN, also known as the "tuberculum acousticum") differs from the ventral portion of the CN as it not only projects to the Inferior Colliculus (IC) but also receives efferent innervation from auditory cortex, superior olivary complex and inferior colliculus. Thus, the DCN is thought to be involved with more complex auditory processing, rather than merely transferring information. The architecture and wiring of the DCN is related to that of the cerebellum, a concept that currently is important in theories of DCN function.
The fusiform (also called pyramidal) cells that dominate the DCN can be excited or inhibited by sound, and are located solely within the DCN. The fusiform cells are the target of two different excitatory systems. The first system arises from the auditory nerve, and carries acoustic information. The second set of inputs is relayed through a set of small cells called "granule" cells in the cochlear nucleus. The granule cells in turn are the target of a number of different inputs, including both those involved in auditory processing and, at least in lower mammals, somatosensory inputs associated with the head, the ear, and the jaw.
The cells in the DCN have very complex frequency intensity tuning curves. For any given cell, the firing rate may be very rapid in response to a low intensity sound at one frequency and then fall below the spontaneous rate with only a small increment in stimulus frequency or intensity. The firing rate may then increase with another increment in intensity or frequency. The fusiform cells are excited by wide band noise.
While the VCN bushy cells aid in the location of a sound stimulus on the horizontal axis, fusiform cells may participate in localization of the sound stimulus on the vertical axis. With the combined power of these two types of cells, an ordinary person can locate where a firework explodes without the use of his eyes.
Brain: rhombencephalon (hindbrain)
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