Re: Traveling waves or resonance?

[Martin Braun <nombraun@xxxxxxxxx>]

Richard F. Lyon wrote on October 20:

> Ren's statement that "In sensitive cochleae, the cochlear partition
> vibration at a given location shows a maximum response to a stimulus
> at the CF, falls off quickly at frequencies above or below the CF,
> and forms a sharp peak in magnitude transfer functions" has been
> interpreted by some as saying that the response is fairly "symmetric"
> about CF.  But the data do not show that, as Fig. 4C makes most
> clear.

Dick, Fig. 4C is not the right one to explore the symmetry question. The
most straightforward figure in this respect is Fig. 1A, as all unbiased
readers will see immediately:

Full text article:
http://www.pnas.org/cgi/content/full/99/26/17101

Figure 1 only:
http://www.pnas.org/cgi/content/full/99/26/17101/F1

Here we can see that the curves for 10, 20, 30, 40, and 50 dB show
symmetrical peaks. From 60 to 90 dB then, they are increasingly asymmetrical
with longer and shallower slopes towards the basal side. This figure
accurately reflects a condition of local resonance up to ca 60 dB, and an
additional basilar membrane traveling wave above ca 60 dB. All this has been
discussed in detail on the Cochlea List:

http://mimosa1.incubator.uiuc.edu/pipermail/cochlea/2002-December/001546.html

http://mimosa1.incubator.uiuc.edu/pipermail/cochlea/2002-December/001550.html

It is no accident, and not based on the errors of hundreds of readers, that
this paper is widely discussed as a turning point in inner ear research.

Martin

----------------------------
Martin Braun
Neuroscience of Music
S-671 95 Klässbol
Sweden
web site: http://w1.570.telia.com/~u57011259/index.htm