Subject: Re: mechanical cochlear model From: Peter van Hengel <pwj.vanhengel@xxxxxxxx> Date: Mon, 15 Mar 2010 13:17:30 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--0016e6da2e7e7ce01a0481d5dd66 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Dear Martin, 2010/3/15 Martin Braun <nombraun@xxxxxxxx> > Peter van Hengel wrote: > > I don't think there is a question whether or not there is a traveling wav= e >> in the cochlea. Fluid mechanics dictates that there has to be one. >> > > There has to be one, if a volume shift of cochlear fluids occurs. Such a > volume shift apparently occurs at high sound levels (>60 dB SPL). However= , > to induce sound waves in the cochlear fluids and also a hair cell respons= e > there is no need at all for a volume shift. This was recently demonstrate= d > by Huber et al. (2008) in a series of elegant experiments: > > http://www.neuroscience-of-music.se/Huber.htm > > In other words, sound waves can enter the cochlea and excite hair cells > without a fluid displacement and without causing a traveling wave. > > Sorry, I did not state that there had to be bet influx at the stapes or a volume shift a you name it. Any fluid motion (such as caused by a rocking stapes) will cause a travelling wave. Even the minute fluid displacements i= n a compession wave will cause a traveling wave. > > The problem I see with a compression wave being the stimulus and the >> haircells acting as pressure sensors ..... >> > > Hair cells need not be pressure sensors for a response to sound waves > (compression waves). The "hairs" of the hair cells can act as wave > detectors. Already today we see that they apparently do this in lizard ea= rs. > Manley (2006) measured spontaneous otoacoustic emissions (SOAEs) from ten > lizard species that have no tectorial membranes. In these animals > free-standing hair bundles vibrate through their own motor mechanism and > thereby produce sound waves in the inner ear fluids that are measurable f= rom > the outside. There is no reason why this process should not work in rever= se > as well, such that hair bundles respond to sound waves that have entered = the > inner ear fluids from the outside. > > Manley GA (2006) Spontaneous otoacoustic emissions from free-standing > stereovillar bundles of ten species of lizard with small papillae. Hear R= es > 212, 33-47. http://www.ncbi.nlm.nih.gov/pubmed/16307854 > > I am sure hair bundles can move and serve as wave detectors. As a matter of fact I strongly support that view. This implies that there is fluid motion which stimulates the hair cells. And as I said before, fluid motion implies a traveling wave. A tectorial membrane is not necessary to get fluid motion. There can be fluid motion without a membrane. But if there is both fluid motion and a membrane there will be a traveling wave. Peter > > 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 > --0016e6da2e7e7ce01a0481d5dd66 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Dear Martin,<br><br> <div class=3D"gmail_quote">2010/3/15 Martin Braun <span dir=3D"ltr"><<a = href=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"> <div class=3D"im">Peter van Hengel wrote:<br><br> <blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex= ; PADDING-LEFT: 1ex" class=3D"gmail_quote">I don't think there is a que= stion whether or not there is a traveling wave<br>in the cochlea. Fluid mec= hanics dictates that there has to be one.<br> </blockquote><br></div>There has to be one, if a volume shift of cochlear f= luids occurs. Such a volume shift apparently occurs at high sound levels (&= gt;60 dB SPL). However, to induce sound waves in the cochlear fluids and al= so a hair cell response there is no need at all for a volume shift. This wa= s recently demonstrated by Huber et al. (2008) in a series of elegant exper= iments:<br> <br><a href=3D"http://www.neuroscience-of-music.se/Huber.htm" target=3D"_bl= ank">http://www.neuroscience-of-music.se/Huber.htm</a><br><br>In other word= s, sound waves can enter the cochlea and excite hair cells without a fluid = displacement and without causing a traveling wave.<br> <br></blockquote> <div>=A0</div> <div>Sorry, I did not state that there had to be bet influx at the stapes o= r a volume shift a you name it. Any fluid motion (such as caused by a rocki= ng stapes) will cause a travelling wave. Even the minute fluid displacement= s in a compession wave will cause a traveling wave.</div> <div>=A0</div> <blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex= ; PADDING-LEFT: 1ex" class=3D"gmail_quote"><br> <blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex= ; PADDING-LEFT: 1ex" class=3D"gmail_quote"> <div class=3D"im">The problem I see with a compression wave being the stimu= lus and the<br></div>haircells acting as pressure sensors .....<br></blockq= uote><br>Hair cells need not be pressure sensors for a response to sound wa= ves (compression waves). The "hairs" of the hair cells can act as= wave detectors. Already today we see that they apparently do this in lizar= d ears. Manley (2006) measured spontaneous otoacoustic emissions (SOAEs) fr= om ten lizard species that have no tectorial membranes. In these animals fr= ee-standing hair bundles vibrate through their own motor mechanism and ther= eby produce sound waves in the inner ear fluids that are measurable from th= e outside. There is no reason why this process should not work in reverse a= s well, such that hair bundles respond to sound waves that have entered the= inner ear fluids from the outside.<br> <br>Manley GA (2006) Spontaneous otoacoustic emissions from free-standing s= tereovillar bundles of ten species of lizard with small papillae. Hear Res = 212, 33-47. <a href=3D"http://www.ncbi.nlm.nih.gov/pubmed/16307854" target= =3D"_blank">http://www.ncbi.nlm.nih.gov/pubmed/16307854</a>=20 <div> <div></div> <div class=3D"h5"><br></div></div></blockquote> <div>=A0</div> <div>I am sure hair bundles can move and serve as wave detectors. As a matt= er of fact I strongly support that view. This implies that there is fluid m= otion which stimulates the hair cells. And as I said before, fluid motion i= mplies a traveling wave.</div> <div>=A0</div> <div>A tectorial membrane is not necessary to get fluid motion. There can b= e fluid motion without a membrane. But if there is both fluid motion and a = membrane there will be a traveling wave.</div> <div>=A0</div> <div>Peter</div> <blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex= ; PADDING-LEFT: 1ex" class=3D"gmail_quote"> <div> <div class=3D"h5"><br>Martin<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></div></di= v></blockquote></div><br> --0016e6da2e7e7ce01a0481d5dd66--