Dr. Robert Fettiplace
Department of Neuroscience
The tonotopic organization of the vertebrate cochlea
Each auditory nerve fiber is tuned to a particular frequency known as the characteristic frequency (CF). The CFs are arranged along the basilar membrane, increasing exponentially from the cochlear apex to base. Knowledge of this tonotopic map’, the topography of the CFs, is necessary in designing cochlear implants to match electrode position to frequency. The form of the map is the same, with few exceptions, in most amniotes (reptiles, birds and mammals), and is most likely established embryonically by gradients in morphogens like sonic hedgehog. I will review evidence for the developmental origin of the map in the chicken and the mouse and discuss why it is preserved at higher auditory levels.