Subject: Re: mechanical cochlear model From: Peter van Hengel <pwj.vanhengel@xxxxxxxx> Date: Wed, 2 Jun 2010 12:46:53 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--00163646d270df20f6048809cebe Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Dear Martin, interesting results no doubt, but once again I must protest against the conclusions. As I have stated before it is not so easy to abolish or greatl= y reduce the traveling wave in the cochlea. Any motion of the fluid, in combination with the flexibility of the BM, will cause a traveling wave, even if you severely influence the boundary conditions. Oversimplification of fluid mechanics in the cochlea has led to erroneous conclusions before... Just a warning against drawing conclusions too rapidly. Regards, Peter 2010/6/2 Martin Braun <nombraun@xxxxxxxx> > Dear List, > > New data have appeared that are again consistent with each of the followi= ng > two hypotheses: > > A. Cochlear macromechanics has no role in hair cell excitation near > threshold of hearing. > B. Cochlear macromechanics has an important role in hair cell protection = at > excessively high sound levels. > > http://www.neuroscience-of-music.se/Sohmer2.htm > > Enjoy, > > Martin > > > --------------------------------------------------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Kl=E4ssbol > Sweden > email: nombraun@xxxxxxxx > web site: http://www.neuroscience-of-music.se/index.htm > > > > > > ----- Original Message ----- From: "Martin Braun" <nombraun@xxxxxxxx> > To: <AUDITORY@xxxxxxxx> > Sent: Saturday, March 06, 2010 10:29 PM > Subject: 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 presse= s > the basilar membrane flat upon the bony cochlear wall of the scala timpan= i: > > http://www.neuroscience-of-music.se/Nageris.htm > > http://www.neuroscience-of-music.se/Xenellis.htm > > > 2) It is a well established observation for more than 50 years that closu= re > 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. > > http://www.neuroscience-of-music.se/Sohmer.htm > > > Martin > > > --------------------------------------------------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Kl=E4ssbol > Sweden > email: nombraun@xxxxxxxx > web site: http://www.neuroscience-of-music.se/index.htm --00163646d270df20f6048809cebe Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div>Dear Martin,</div> <div>=A0</div> <div>interesting results no doubt, but once again I must protest against th= e conclusions. As I have stated before it is not so easy to abolish or grea= tly reduce the traveling wave in the cochlea. Any motion of the fluid, in c= ombination with the flexibility of the BM, will cause a traveling wave, eve= n if you severely influence the boundary conditions.</div> <div>Oversimplification of fluid mechanics in the cochlea has led to errone= ous conclusions before...</div> <div>Just a warning against drawing conclusions too rapidly.<br></div> <div>Regards,</div> <div>Peter<br></div> <div class=3D"gmail_quote">2010/6/2 Martin Braun <span dir=3D"ltr"><<a h= ref=3D"mailto:nombraun@xxxxxxxx">nombraun@xxxxxxxx</a>></span><br> <blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex= ; PADDING-LEFT: 1ex" class=3D"gmail_quote">Dear List,<br><br>New data have = appeared that are again consistent with each of the following two hypothese= s:<br> <br>A. Cochlear macromechanics has no role in hair cell excitation near thr= eshold of hearing.<br>B. Cochlear macromechanics has an important role in h= air cell protection at excessively high sound levels.<br><br><a href=3D"htt= p://www.neuroscience-of-music.se/Sohmer2.htm" target=3D"_blank">http://www.= neuroscience-of-music.se/Sohmer2.htm</a><br> <br>Enjoy,<br><br>Martin<br><br><br>---------------------------------------= ------------------------------<br>Martin Braun<br>Neuroscience of Music<br>= S-671 95 Kl=E4ssbol<br>Sweden<br>email: <a href=3D"mailto:nombraun@xxxxxxxx= m" target=3D"_blank">nombraun@xxxxxxxx</a><br> web site: <a href=3D"http://www.neuroscience-of-music.se/index.htm" target= =3D"_blank">http://www.neuroscience-of-music.se/index.htm</a><br><br><br><b= r><br><br>----- Original Message ----- From: "Martin Braun" <<= a href=3D"mailto:nombraun@xxxxxxxx" target=3D"_blank">nombraun@xxxxxxxx</= a>><br> To: <<a href=3D"mailto:AUDITORY@xxxxxxxx" target=3D"_blank">AUDIT= ORY@xxxxxxxx</a>><br>Sent: Saturday, March 06, 2010 10:29 PM<br>S= ubject: Re: mechanical cochlear model<br><br><br>While the cochlear traveli= ng wave has appeared in numerous empirical reports<br> on real physical models and real biological animals, it's function in<b= r>hearing is not yet universally appreciated. Some people still think that = it<br>provides the well known frequency selectivity that we observe in the<= br> auditory nerve. This view, however, has been proved wrong by multiple direc= t<br>experimental evidence. Just consider two bodies of evidence:<br><br>1)= Hearing sensitivity is not affected, when endolymphatic hydrops presses<br= > the basilar membrane flat upon the bony cochlear wall of the scala timpani:= <br><br><a href=3D"http://www.neuroscience-of-music.se/Nageris.htm" target= =3D"_blank">http://www.neuroscience-of-music.se/Nageris.htm</a><br><br><a h= ref=3D"http://www.neuroscience-of-music.se/Xenellis.htm" target=3D"_blank">= http://www.neuroscience-of-music.se/Xenellis.htm</a><br> <br><br>2) It is a well established observation for more than 50 years that= closure<br>of the round window does not affect hearing sensitivity. This m= eans that a<br>pressure difference across the basilar membrane and a result= ing traveling<br> wave cannot be a necessary condition of hair cell excitation. Recently,<br>= Perez et al. (2009) reported that closure of the round window not only<br>l= eaves hearing sensitivity unchanged but increases cochlear vulnerability at= <br> high sound levels. This second new observation is a further compelling<br>i= ndication as to the real function of the cochlear traveling wave.<br><br><a= href=3D"http://www.neuroscience-of-music.se/Sohmer.htm" target=3D"_blank">= http://www.neuroscience-of-music.se/Sohmer.htm</a><br> <br><br>Martin<br><br><br>-------------------------------------------------= --------------------<br><font color=3D"#888888">Martin Braun<br>Neuroscienc= e of Music<br>S-671 95 Kl=E4ssbol<br>Sweden<br>email: <a href=3D"mailto:nom= braun@xxxxxxxx" target=3D"_blank">nombraun@xxxxxxxx</a><br> web site: <a href=3D"http://www.neuroscience-of-music.se/index.htm" target= =3D"_blank">http://www.neuroscience-of-music.se/index.htm</a> </font></bloc= kquote></div><br> --00163646d270df20f6048809cebe--