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Re: mechanical cochlear model

While the cochlear traveling wave has appeared in numerous empirical reports on real physical models and real biological animals, it's function in hearing is not yet universally appreciated. Some people still think that it provides the well known frequency selectivity that we observe in the auditory nerve. This view, however, has been proved wrong by multiple direct experimental evidence. Just consider two bodies of evidence:

1) Hearing sensitivity is not affected, when endolymphatic hydrops presses the basilar membrane flat upon the bony cochlear wall of the scala timpani:



2) It is a well established observation for more than 50 years that closure of the round window does not affect hearing sensitivity. This means that a pressure difference across the basilar membrane and a resulting traveling wave cannot be a necessary condition of hair cell excitation. Recently, Perez et al. (2009) reported that closure of the round window not only leaves hearing sensitivity unchanged but increases cochlear vulnerability at high sound levels. This second new observation is a further compelling indication as to the real function of the cochlear traveling wave.



Martin Braun
Neuroscience of Music
S-671 95 Klässbol
email: nombraun@xxxxxxxxx
web site: http://www.neuroscience-of-music.se/index.htm