Re: mechanical cochlear model (Daniel TAFT )

Subject: Re: mechanical cochlear model From: Daniel TAFT <DTAFT@xxxxxxxx> Date: Mon, 8 Mar 2010 13:39:21 +1100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY> --_000_18C7138F7DC13F498AE19062AC987443026F2DF3C9franklinmedot_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I am also unconvinced re: discarding the traveling wave model. I don't real= ly understand why the traveling wave can't provide the broad filtering, wit= h outer hair cells providing the sharpening. Seems more robust than having = nicely spaced resonators. Anyway, I'm going to plug my own recently published thesis on traveling wav= es for cochlear implants here: It's freely available at http://repository.unimelb.edu.au/10187/5783 And there's a new paper here too: http://ieeexplore.ieee.org/xpl/freeabs_al= l.jsp?arnumber=3D5290084 I will point out that it's a signal processing thesis about employing filte= r delays in a prosthesis, rather than understanding their physical basis, a= nd doesn't actually contain any mechanical modeling of the cochlea. But rea= ders of this thread might be interested nonetheless. Daniel Taft. From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxx= ILL.CA] On Behalf Of David Mountain Sent: Monday, 8 March 2010 3:57 AM To: AUDITORY@xxxxxxxx Subject: Re: [AUDITORY] mechanical cochlear model The cochlear traveling wave is still alive and well. We may debate the det= ails of how the cochlear amplifier works but all the fully developed comput= ational models start with the known physical properties of the cochlear flu= ids and the basilar membrane and some basic Newtonian physics. These model= s all support the classical traveling wave theory. Here are some of my com= ments 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 dif= ferent regions of the cochlea. 4) There is some very good evidence that there is a third window in the coc= hlea 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<mailto= :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 extending 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 guinea pig (R&N 1997, PNAS 94, 2660). C) Lonsbury-Martin & Martin found histologically a gap only 60-70 um wide 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 to 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-fold (p. 476 of Exp in Hearing). 3. Some workers (eg, Stenfelt) find that the spiral lamina is as flexible a= s the basilar membrane, removing another avenue by which tonotopic tuning can be achieved - because its width is about constant. (Stenfelt 2003, Hear Res 181, 131). 4. Cases are reported where a person has been found to possess holes in the basilar membrane - and the holes don't appear to affect hearing. In some birds, there is a naturally occurring shunt called the ductis brevis, which connects the upper and lower chambers at the basal end. Yet these birds hea= r perfectly well nonetheless. 5. People lacking a middle ear can still hear (and yet pressure on the oval 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 most 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<mailto:AUDITORY@xxxxxxxx>] On Beh= alf Of Martin Braun > Sent: Sunday, 7 March 2010 7:29 AM > To: AUDITORY@xxxxxxxx<mailto: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<mailto:nombraun@xxxxxxxx> > web site: http://www.neuroscience-of-music.se/index.htm > -- David C. Mountain, Ph.D. Professor of Biomedical Engineering Boston University 44 Cummington St. Boston, MA 02215 Email: dcm@xxxxxxxx<mailto:dcm@xxxxxxxx> Website: http://www.bu.edu/hrc/research/laboratories/auditory-biophysics/ Phone: (617) 353-4343 FAX: (617) 353-6766 Office: ERB 413 --_000_18C7138F7DC13F498AE19062AC987443026F2DF3C9franklinmedot_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <html xmlns:v=3D"urn:schemas-microsoft-com:vml" xmlns:o=3D"urn:schemas-micr= osoft-com:office:office" xmlns:w=3D"urn:schemas-microsoft-com:office:word" = xmlns:m=3D"http://schemas.microsoft.com/office/2004/12/omml" xmlns=3D"http:= //www.w3.org/TR/REC-html40"> <head> <meta http-equiv=3DContent-Type content=3D"text/html; charset=3Diso-8859-1"= > <meta name=3DGenerator content=3D"Microsoft Word 12 (filtered medium)"> <style>  </style>  </head> <body lang=3DEN-US link=3Dblue vlink=3Dpurple> <div class=3DSection1> I am also unconvinced re: discarding the traveling wave mode= l. I don’t really understand why the traveling wave can’t provide th= e broad filtering, with outer hair cells providing the sharpening. Seems more robust than having nicely spaced resonators.<o:p></o:p> <o:p> </o:p> Anyway, I’m going to plug my own recently published th= esis on traveling waves for cochlear implants here:<o:p></o:p> <o:p> </o:p> It’s freely available at <a href=3D"http://repository.unimelb.edu.au/10187/5783">http://repository.unim= elb.edu.au/10187/5783</a> <o:p></o:p> And there’s a new paper here too: <a href=3D"http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=3D5290084">= http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=3D5290084</a><o:p><= /o:p> <o:p> </o:p> I will point out that it’s a signal processing thesis = about employing filter delays in a prosthesis, rather than understanding their physical basis, and doesn’t actually contain any mechanical modeling = of the cochlea. But readers of this thread might be interested nonetheless. <o= :p></o:p> <o:p> </o:p> Daniel Taft.<o:p></o:p> <o:p> </o:p> <o:p> </o:p> <div style=3D'border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm = 0cm 0cm'> From: AUDITORY - Re= search in Auditory Perception [mailto:AUDITORY@xxxxxxxx On Behalf Of </= b>David Mountain Sent: Monday, 8 March 2010 3:57 AM To: AUDITORY@xxxxxxxx Subject: Re: [AUDITORY] mechanical cochlear model<o:p></o:p><= /p> </div> <o:p> </o:p> <div> 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 properti= es 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:<o:p></o:p> </div> <div> <o:p> </o:p> </div> 1) The peak of the traveling wave is much broader than= one would expect for a simple resonant system.  The gerbil basilar membran= e 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.<o:p></o:p> <div> <o:p> </o:p> </div> <div> 2) The jury is still out on the basilar membrane stiff= ness gradient.  Emadi et al (2004) Hear. Res. found a larger gradient than = what Ram Naidu and I found.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> 3)  Even if the Naidu and Mountain stiffness data= are correct, the cochlear frequency range could be the result of different mode= s of vibration in different regions of the cochlea.<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> 4) There is some very g= ood evidence that there is a third window in the cochlea from H. Nakajima et al that was presented at this year's ARO meeting.<o:p></o:p> <div> On Sat, Mar 6, 2010 at 10:00 PM, Andrew Bell <<a href=3D"mailto:andrew.bell@xxxxxxxx">andrew.bell@xxxxxxxx</a>> wrote= :<o:p></o:p> In addition to Martin's 2 pieces of evidence against t= he 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 exten= ding 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 guinea pig (R&N 1997, PNAS 94, 2660).   C) Lonsbury-Martin & Martin found histologically a gap only 60-7= 0 um wide 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 frequen= cy selectivity between basilar membrane and neural responses has always been,<= br> 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 to<= br> 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-fold<= br> (p. 476 of Exp in Hearing). 3. Some workers (eg, Stenfelt) find that the spiral lamina is as flexible a= s the basilar membrane, removing another avenue by which tonotopic tuning can= be achieved - because its width is about constant. (Stenfelt 2003, Hear Res= 181, 131). 4. Cases are reported where a person has been found to possess holes in the= basilar membrane - and the holes don't appear to affect hearing. In some<br= > birds, there is a naturally occurring shunt called the ductis brevis, which= connects the upper and lower chambers at the basal end. Yet these birds hea= r perfectly well nonetheless. 5. People lacking a middle ear can still hear (and yet pressure on the oval= and round windows should in these cases be equal). 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 compressible). I've mentioned various publications previously, but the most= comprehensive one is my thesis. It discusses the above anomalies, and others, in some detail - the link is <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/in= dex.html</a> 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<b= r> 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<o:p></o:p> <div> <div> > -----Original Message----- > From: AUDITORY - Research in Auditory Perception > [mailto:<a href=3D"mailto:AUDITORY@xxxxxxxx">AUDITORY@xxxxxxxx= ILL.CA</a>] On Behalf Of Martin Braun > Sent: Sunday, 7 March 2010 7:29 AM > To: <a href=3D"mailto:AUDITORY@xxxxxxxx">AUDITORY@xxxxxxxx= CA</a> > 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<= br> > hearing is not yet universally appreciated. Some people still > think that it > provides the well known frequency selectivity that we observe in the<b= r> > 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: > > <a href=3D"http://www.neuroscience-of-music.se/Nageris.htm" target=3D"= _blank">http://www.neuroscience-of-music.se/Nageris.htm</a> > > <a href=3D"http://www.neuroscience-of-music.se/Xenellis.htm" target=3D= "_blank">http://www.neuroscience-of-music.se/Xenellis.htm</a> > > > 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. > > <a href=3D"http://www.neuroscience-of-music.se/Sohmer.htm" target=3D"_= blank">http://www.neuroscience-of-music.se/Sohmer.htm</a> > > > Martin > > > ---------------------------------------------------------------------<= br> > Martin Braun > Neuroscience of Music > S-671 95 Kl=E4ssbol > Sweden > email: <a href=3D"mailto:nombraun@xxxxxxxx">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> ><o:p></o:p> </div> </div> </div> -- David C. Mountain, Ph.D. Professor of Biomedical Engineering Boston University 44 Cummington St. Boston, MA 02215 Email:   <a href=3D"mailto:dcm@xxxxxxxx">dcm@xxxxxxxx</a> Website: <a href=3D"http://www.bu.edu/hrc/research/laboratories/auditory-biophysics/">h= ttp://www.bu.edu/hrc/research/laboratories/auditory-biophysics/</a> Phone:   (617) 353-4343 FAX:     (617) 353-6766 Office:  ERB 413<o:p></o:p> </div> </div> </body> </html> --_000_18C7138F7DC13F498AE19062AC987443026F2DF3C9franklinmedot_--

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