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Re: cochlear discussions

Dear All

I apologise if my own evolutionary perspective has fallen on deaf
ears (excuse pun) due to use of highly technical jargon. However, I
do believe that in this case it is of interest to the general list
readership. So let me summarise this view in a less technical manner.

1. The travelling wave phenomenon has evolved independently at least
three times during the course of evolution.

2. The principles of parsimony and evolutionary consistency would
suggest that a single theory should account for all examples of the
same phenomenon.

3. The essence of  Lighthill theory is that a travelling wave can be
described by a chain of masses and springs (if you like mechanical
analogies) or inductances and capacitances (if you like electrical

4. The implication of Lewis's (1988) interpretation of the three
structures in 1. (amphibian papilla (AP),  amphibian sacculus (S) and
mamallian cochlear (C)) from the Lighthill perspective can be
summarised as follows.

structure        springs         masses

AP                hair-cells      tectorium
S                   hair-cells      otoconial membrane
C                  OHCs          tectorial membrane

5. Conclusion. Irrespective of whether one goes for the TW theory
or the resonance theory (I am agnostic on this), evolutionary
consistency points to the interaction between the OHCs and the
tectorial membrane as being the important elements in the frequency
selective properties of the mamallian ear. This is also consistent
with the efferent system playing an active role in the selectivity,
since in part the spring-like (two-way transductive) property of the
OHCs may be neurobiological, rather than purely mechanical.

6. Surely this is of interest to all list members, not least because
many of us have been labouring under the possibly false belief that
the frequency selective properties of mamallian ear are due to the
mechanical properties of the basilar membrane.

I rest my case.

Neil Todd

> Date:    Wed, 12 Jul 2000 09:26:50 -0400
> From:    Robert Zatorre <md37@MUSICA.MCGILL.CA>
> Subject: cochlear discussions
> If I can just add a small suggestion about this discussion.
> Perhaps the people involved in the discussion can use a bit of
> judgment: if the points being discussed are highly technical and/or
> very specifically directed at one or two individuals, then a posting
> to those individuals is appropriate. We don't all need to read about
> it.
> On the other hand, if you have a more general point to make, or wish
> to invite discussion, then a posting to the list is certainly
> appropriate and very welcome. However, in this case, please be aware
> that those of us who are not biophysicists will not have a clue what
> you're talking about if you use highly technical jargon. Similarly,
> if you are addressing the comments to a broad group, please avoid
> references that only one or two people will follow--a lot of the
> stuff posted is difficult to parse and seems destined for an
> "in-group."
> With a little thought about the recipients of your messages, these
> kinds of discussions can be very fruitful and enlightening, but
> otherwise they make most of us hit the old delete button rather
> quickly.
> Thank you
> Robert

> Date:    Tue, 11 Jul 2000 18:37:48 +1000
> From:    Andrew Bell <bellring@SMARTCHAT.NET.AU>
> Subject: Re: Cochlear mechanics
> However, I believe that circumscribing the range of discussions on
> this list
> probably isn't necessary. People who aren't interested in a certain subject
> heading can just push the Delete button, as they always have (that's what
> subject headers are for). However, if enough people thought a second list
> was a good idea, I would go along with the majority's wishes.
> What do other list members think?
> Andrew.
> -----Original Message-----
> From: AUDITORY Research in Auditory Perception
> [mailto:AUDITORY@LISTS.MCGILL.CA]On Behalf Of Al Bregman
> Sent: Tuesday, 11 July 2000 6:59
> Subject: Cochlear mechanics
> Dear List,
> I believe that we have now heard most views on the very important issue of
> cochlear mechanics, culminating in the excellent summary by Eckard
> Blumschein.  I wonder whether now isn't the time for those researchers
> who want to continue the discussion to do so among themselves, perhaps on a
> new sublist, as suggested by Jont Allen, where the issues could get debated
> in full at a technical level which is probably more detailed than the rest
> of us need to know.
> Al
> -------------------------------------------------
> Albert S. Bregman, Emeritus Professor
> Dept of Psychology, McGill University
> 1205 Docteur Penfield Avenue
> Montreal, QC, Canada H3A 1B1
> Tel:  +1 (514) 398-6103
> Fax: +1 (514) 398-4896