Editing Tonotopy (section)

{{short description|Arrangement of sound frequency processing in the brain}}
In [[physiology]], '''tonotopy''' (from Greek tono = frequency and topos = place) is the spatial arrangement of where sounds of different frequency are processed in the brain. Tones close to each other in terms of frequency are represented in [[topology|topologically]] neighbouring regions in the brain. Tonotopic maps are a particular case of [[topographic map (Neuroanatomy)|topographic]] organization, similar to [[retinotopy]] in the visual system.

Tonotopy in the auditory system begins at the [[cochlea]], the small snail-like structure in the inner ear that sends information about sound to the brain.  Different regions of the [[basilar membrane]] in the [[organ of Corti]], the sound-sensitive portion of the cochlea, vibrate at different sinusoidal frequencies due to variations in thickness and width along the length of the membrane. Nerves that transmit information from different regions of the basilar membrane therefore encode frequency tonotopically.

This tonotopy then projects through the [[Auditory system#Central auditory system|vestibulocochlear nerve and associated midbrain structures]] to the primary auditory cortex via the auditory radiation pathway.
Throughout this radiation, organization is linear with relation to placement on the organ of Corti, in accordance to the best frequency response (that is, the frequency at which that neuron is most sensitive) of each neuron. However, [[binaural fusion]] in the [[superior olivary complex]] onward adds significant amounts of information encoded in the signal strength of each ganglion. Thus, the number of tonotopic maps varies between species and the degree of binaural synthesis and separation of sound intensities; in humans, six tonotopic maps have been identified in the primary auditory cortex.<ref name="Talavage 2004">{{cite journal | vauthors = Talavage TM, Sereno MI, Melcher JR, Ledden PJ, Rosen BR, Dale AM | title = Tonotopic organization in human auditory cortex revealed by progressions of frequency sensitivity | journal = Journal of Neurophysiology | volume = 91 | issue = 3 | pages = 1282–96 | date = March 2004 | pmid = 14614108 | doi = 10.1152/jn.01125.2002 | url = http://www.cogsci.ucsd.edu/~sereno/papers/AuditoryMaps04.pdf }}</ref>