Re: mechanical cochlear model (David Mountain )


Subject: Re: mechanical cochlear model
From:    David Mountain  <dcm@xxxxxxxx>
Date:    Sun, 7 Mar 2010 11:57:21 -0500
List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>

--00151747bdbe961b0a048138d732 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable The cochlear traveling wave is still alive and well. We may debate the details of how the cochlear amplifier works but all the fully developed computational models start with the known physical properties of the cochlear fluids and the basilar membrane and some basic Newtonian physics. These models all support the classical traveling wave theory. Here are some of my comments w/r to some of the arguments against the traveling wave= : 1) The peak of the traveling wave is much broader than one would expect for a simple resonant system. The gerbil basilar membrane is only ~12 mm long so a peak extending over 0.5 mm (8%) is pretty broad for a cochlea that is tuned from 300-60,000 Hz. 2) The jury is still out on the basilar membrane stiffness gradient. Emadi et al (2004) Hear. Res. found a larger gradient than what Ram Naidu and I found. 3) Even if the Naidu and Mountain stiffness data are correct, the cochlear frequency range could be the result of different modes of vibration in different regions of the cochlea. 4) There is some very good evidence that there is a third window in the cochlea from H. Nakajima et al that was presented at this year's ARO meeting. On Sat, Mar 6, 2010 at 10:00 PM, Andrew Bell <andrew.bell@xxxxxxxx> wrote= : > In addition to Martin's 2 pieces of evidence against the traveling wave > model, we can add: > > 1. The peak of the traveling wave is unrealistically sharp. > > A) In a gerbil, Ren found that the peak occurred over a region extendin= g > less than 0.5 mm at 16 kHz (Ren 2002, PNAS 99, 17101). > > B) Russell & Nilsen saw a peak only 0.15-1 mm wide at 15 kHz in a guine= a > pig (R&N 1997, PNAS 94, 2660). > > C) Lonsbury-Martin & Martin found histologically a gap only 60-70 um wi= de > due to damaging pure tone levels applied to monkeys' ears (L-M & M 1987, > JASA 81, 1507). > > I quote Jont Allen's remark from 2001 that "the discrepancy in frequency > selectivity between basilar membrane and neural responses has always been= , > and still is, the most serious problem for the cochlear modelling > community." Jont, do you still feel that way? > > 2. The variation is stiffness is inadequate to tune the cochlea from 20 t= o > 20000 Hz. Three decades of frequency calls for a million times variation = in > stiffness (more than between foam rubber and tungsten), and this is in > contrast to measurements of 2 or 3 orders at most. See Naidu & Mountain > 1998, Hear Res 124, 124. Bekesy found the value to be about a hundred-fol= d > (p. 476 of Exp in Hearing). > > 3. Some workers (eg, Stenfelt) find that the spiral lamina is as flexible > as > the basilar membrane, removing another avenue by which tonotopic tuning c= an > be achieved - because its width is about constant. (Stenfelt 2003, Hear R= es > 181, 131). > > 4. Cases are reported where a person has been found to possess holes in t= he > basilar membrane - and the holes don't appear to affect hearing. In some > birds, there is a naturally occurring shunt called the ductis brevis, whi= ch > connects the upper and lower chambers at the basal end. Yet these birds > hear > perfectly well nonetheless. > > 5. People lacking a middle ear can still hear (and yet pressure on the ov= al > and round windows should in these cases be equal). > > Together, all these anomalies cast doubt on the adequacy of the traveling > wave model. I think the TW model, as currently framed, cannot work at low > sound pressure levels, and have formulated a resonance model in which the > effective stimulus is the fast pressure wave (not the pressure difference > across the membrane) and where the OHCs are pressure sensors (they are > compressible). I've mentioned various publications previously, but the mo= st > comprehensive one is my thesis. It discusses the above anomalies, and > others, in some detail - the link is > http://thesis.anu.edu.au/public/adt-ANU20080706.141018/index.html > > The traveling wave can drive some passive processes, but in terms of > efficiency we need an active system, and I think that here we need living > pressure sensors (outer hair cells) forming resonant elements. > > > Andrew. > > > > Andrew Bell > Research School of Biology (RSB) > College of Medicine, Biology and Environment > The Australian National University > Canberra, ACT 0200, Australia > > > > > > -----Original Message----- > > From: AUDITORY - Research in Auditory Perception > > [mailto:AUDITORY@xxxxxxxx On Behalf Of Martin Braun > > Sent: Sunday, 7 March 2010 7:29 AM > > To: AUDITORY@xxxxxxxx > > Subject: Re: [AUDITORY] 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: > > > > 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 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. > > > > 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 > > > --=20 David C. Mountain, Ph.D. Professor of Biomedical Engineering Boston University 44 Cummington St. Boston, MA 02215 Email: dcm@xxxxxxxx Website: http://www.bu.edu/hrc/research/laboratories/auditory-biophysics/ Phone: (617) 353-4343 FAX: (617) 353-6766 Office: ERB 413 --00151747bdbe961b0a048138d732 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div>The cochlear traveling wave is still alive and well. =A0We may debate = the details of how the cochlear amplifier works but all the fully developed= computational models start with the known physical properties of the cochl= ear fluids and the basilar membrane and some basic Newtonian physics. =A0Th= ese models all support the classical traveling wave theory. =A0Here are som= e of my comments w/r to some of the arguments against the traveling wave:</= div> <div><br></div>1) The peak of the traveling wave is much broader than one w= ould expect for a simple resonant system. =A0The gerbil basilar membrane is= only ~12 mm long so a peak extending over 0.5 mm (8%) is pretty broad for = a cochlea that is tuned from 300-60,000 Hz.<div> <br></div><div>2) The jury is still out on the basilar membrane stiffness g= radient. =A0Emadi et al (2004) Hear. Res. found a larger gradient than what= Ram Naidu and I found.</div><div><br></div><div>3) =A0Even if the Naidu an= d Mountain stiffness data are correct, the cochlear frequency range could b= e the result of different modes of vibration in different regions of the co= chlea.</div> <div><br></div><div>4) There is some very good evidence that there is a thi= rd window in the cochlea from H. Nakajima et al that was presented at this = year&#39;s ARO meeting.<br><br><div class=3D"gmail_quote">On Sat, Mar 6, 20= 10 at 10:00 PM, Andrew Bell <span dir=3D"ltr">&lt;<a href=3D"mailto:andrew.= bell@xxxxxxxx">andrew.bell@xxxxxxxx</a>&gt;</span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex;">In addition to Martin&#39;s 2 pieces of evi= dence against the traveling wave<br> model, we can add:<br> <br> 1. The peak of the traveling wave is unrealistically sharp.<br> <br> =A0 A) In a gerbil, Ren found that the peak occurred over a region extendi= ng<br> less than 0.5 mm at 16 kHz (Ren 2002, PNAS 99, 17101).<br> <br> =A0 B) Russell &amp; Nilsen saw a peak only 0.15-1 mm wide at 15 kHz in a = guinea<br> pig (R&amp;N 1997, PNAS 94, 2660).<br> <br> =A0 C) Lonsbury-Martin &amp; Martin found histologically a gap only 60-70 = um wide<br> due to damaging pure tone levels applied to monkeys&#39; ears (L-M &amp; M = 1987,<br> JASA 81, 1507).<br> <br> I quote Jont Allen&#39;s remark from 2001 that &quot;the discrepancy in fre= quency<br> selectivity between basilar membrane and neural responses has always been,<= br> and still is, the most serious problem for the cochlear modelling<br> community.&quot; Jont, do you still feel that way?<br> <br> 2. The variation is stiffness is inadequate to tune the cochlea from 20 to<= br> 20000 Hz. Three decades of frequency calls for a million times variation in= <br> stiffness (more than between foam rubber and tungsten), and this is in<br> contrast to measurements of 2 or 3 orders at most. See Naidu &amp; Mountain= <br> 1998, Hear Res 124, 124. Bekesy found the value to be about a hundred-fold<= br> (p. 476 of Exp in Hearing).<br> <br> 3. Some workers (eg, Stenfelt) find that the spiral lamina is as flexible a= s<br> the basilar membrane, removing another avenue by which tonotopic tuning can= <br> be achieved - because its width is about constant. (Stenfelt 2003, Hear Res= <br> 181, 131).<br> <br> 4. Cases are reported where a person has been found to possess holes in the= <br> basilar membrane - and the holes don&#39;t appear to affect hearing. In som= e<br> birds, there is a naturally occurring shunt called the ductis brevis, which= <br> connects the upper and lower chambers at the basal end. Yet these birds hea= r<br> perfectly well nonetheless.<br> <br> 5. People lacking a middle ear can still hear (and yet pressure on the oval= <br> and round windows should in these cases be equal).<br> <br> Together, all these anomalies cast doubt on the adequacy of the traveling<b= r> wave model. I think the TW model, as currently framed, cannot work at low<b= r> sound pressure levels, and have formulated a resonance model in which the<b= r> effective stimulus is the fast pressure wave (not the pressure difference<b= r> across the membrane) and where the OHCs are pressure sensors (they are<br> compressible). I&#39;ve mentioned various publications previously, but the = most<br> comprehensive one is my thesis. It discusses the above anomalies, and<br> others, in some detail - the link is<br> <a href=3D"http://thesis.anu.edu.au/public/adt-ANU20080706.141018/index.htm= l" target=3D"_blank">http://thesis.anu.edu.au/public/adt-ANU20080706.141018= /index.html</a><br> <br> The traveling wave can drive some passive processes, but in terms of<br> efficiency we need an active system, and I think that here we need living<b= r> pressure sensors (outer hair cells) forming resonant elements.<br> <br> <br> Andrew.<br> <br> <br> <br> Andrew Bell<br> Research School of Biology (RSB)<br> College of Medicine, Biology and Environment<br> The Australian National University<br> Canberra, ACT 0200, Australia<br> <div><div></div><div class=3D"h5"><br> <br> <br> <br> &gt; -----Original Message-----<br> &gt; From: AUDITORY - Research in Auditory Perception<br> &gt; [mailto:<a href=3D"mailto:AUDITORY@xxxxxxxx">AUDITORY@xxxxxxxx= ILL.CA</a>] On Behalf Of Martin Braun<br> &gt; Sent: Sunday, 7 March 2010 7:29 AM<br> &gt; To: <a href=3D"mailto:AUDITORY@xxxxxxxx">AUDITORY@xxxxxxxx= CA</a><br> &gt; Subject: Re: [AUDITORY] mechanical cochlear model<br> &gt;<br> &gt;<br> &gt; While the cochlear traveling wave has appeared in numerous<br> &gt; empirical reports<br> &gt; on real physical models and real biological animals, it&#39;s function= in<br> &gt; hearing is not yet universally appreciated. Some people still<br> &gt; think that it<br> &gt; provides the well known frequency selectivity that we observe in the<b= r> &gt; auditory nerve. This view, however, has been proved wrong by<br> &gt; multiple direct<br> &gt; experimental evidence. Just consider two bodies of evidence:<br> &gt;<br> &gt; 1) Hearing sensitivity is not affected, when endolymphatic<br> &gt; hydrops presses<br> &gt; the basilar membrane flat upon the bony cochlear wall of the<br> &gt; scala timpani:<br> &gt;<br> &gt; <a href=3D"http://www.neuroscience-of-music.se/Nageris.htm" target=3D"= _blank">http://www.neuroscience-of-music.se/Nageris.htm</a><br> &gt;<br> &gt; <a href=3D"http://www.neuroscience-of-music.se/Xenellis.htm" target=3D= "_blank">http://www.neuroscience-of-music.se/Xenellis.htm</a><br> &gt;<br> &gt;<br> &gt; 2) It is a well established observation for more than 50<br> &gt; years that closure<br> &gt; of the round window does not affect hearing sensitivity. This<br> &gt; means that a<br> &gt; pressure difference across the basilar membrane and a<br> &gt; resulting traveling<br> &gt; wave cannot be a necessary condition of hair cell excitation.<br> &gt; Recently,<br> &gt; Perez et al. (2009) reported that closure of the round window<br> &gt; not only<br> &gt; leaves hearing sensitivity unchanged but increases cochlear<br> &gt; vulnerability at<br> &gt; high sound levels. This second new observation is a further<br> &gt; compelling<br> &gt; indication as to the real function of the cochlear traveling wave.<br> &gt;<br> &gt; <a href=3D"http://www.neuroscience-of-music.se/Sohmer.htm" target=3D"_= blank">http://www.neuroscience-of-music.se/Sohmer.htm</a><br> &gt;<br> &gt;<br> &gt; Martin<br> &gt;<br> &gt;<br> &gt; ---------------------------------------------------------------------<= br> &gt; Martin Braun<br> &gt; Neuroscience of Music<br> &gt; S-671 95 Kl=E4ssbol<br> &gt; Sweden<br> &gt; email: <a href=3D"mailto:nombraun@xxxxxxxx">nombraun@xxxxxxxx</a><br= > &gt; web site: <a href=3D"http://www.neuroscience-of-music.se/index.htm" ta= rget=3D"_blank">http://www.neuroscience-of-music.se/index.htm</a><br> &gt;<br> </div></div></blockquote></div><br><br clear=3D"all"><br>-- <br><br>David C= . Mountain, Ph.D.<br>Professor of Biomedical Engineering<br><br>Boston Univ= ersity<br>44 Cummington St.<br>Boston, MA 02215<br><br>Email: =A0 <a href= =3D"mailto:dcm@xxxxxxxx">dcm@xxxxxxxx</a><br> Website: <a href=3D"http://www.bu.edu/hrc/research/laboratories/auditory-bi= ophysics/">http://www.bu.edu/hrc/research/laboratories/auditory-biophysics/= </a><br>Phone: =A0 (617) 353-4343<br>FAX: =A0 =A0 (617) 353-6766<br>Office:= =A0ERB 413<br> <br> </div> --00151747bdbe961b0a048138d732--


This message came from the mail archive
/home/empire6/dpwe/public_html/postings/2010/
maintained by:
DAn Ellis <dpwe@ee.columbia.edu>
Electrical Engineering Dept., Columbia University