V ADOHVIFS M f I .11 9f1 I M I IMF9014INFOS AMDIOLHGV KVJ News / At the heart of the matter / Wide Angle / Another perspective / The specialists / 4'5'#4%* #0& &'8'.12/'06 ern processing Hearing really know everything about about everything reallyknow handle high sound volumes, volumes, sound high handle detail, there still mysteries are there detail, how the micromechanics of of micromechanics the how explanation Is hidden in the inthe Is hidden explanation combined with the ability to to ability the with combined Versteegh Ph.D. Versteegh investigates the ear? When looked at In at looked When ear? the the organ of Corti function function Corti of organ the to be solved,The amazing amazing solved,The be to how the stereocilia on the the on stereocilia the how cell's frequency selectivity, cell'sfrequency of Corti in the cochlea. At cochlea. inthe Corti of It Is often heard: we know know we Itheard: Is often still a black box. latter The stillblack a movements of the organ organ the of movements might be true, but do we we do but true, be might processing in the brain is brain inthe processing [email protected] the Rockefeller UniversityRockefeller the performance of the hair hair the of performance a lot about how the ear ear the how about lot a and thus tries to unravel unravel tries to thus and is not explained yet.The yet.The explained isnot functions, but hearing hearing but functions, hair cells perform their their perform cells hair in New New York,in Corstiaen By Leendert van der Ent der van ByLeendert How does Corti's organ Corti's Howdoes FUNDAMENTAL GET LET'S stunning task. stunning

1 the background does not influence hearing dramatical hearing influence not does background the explanation of observations regarding hearing situati hearing regarding observations givin of to explanation dedicated was thesis Ph.D Versteegh's Corstiaen background noise really makes it hard to understand ne understand to hard it makes really noise background ons: A beep-like noise in noise beep-like A ons: ly, but a low frequency frequency low a but ly, arby speech. arby g a scientific scientific a g Wikipedia triguing question on the basic cell level once again once level cell basic the on question triguing h ccla level cochlear The sou nd volum e at the sam e time, represents an extraor an represents time, e sam the at e volum nd sou hl. e i hsfr i P.. hss tte Er the at thesis cochl Ph.D. the his of for this did functioning He the to whole. a d turne first steegh eetvt ihteaiiyt losnevr oud lo very sense also to ability the with selectivity hs rs n eain o akrud os. Verstee noise. background to relation in orks w this aya sytuepandpromance." perform unexplained yet as d an nary inl Ltl i ko a ti moe n, becaus ent, ovem m this t u o ab n know is Little signal. ytm i al t dsigih 01 fequenc diffe cy n e u q fre 0.1% a hearing an distinguish hum to The able is fascinating. is system ance perform the Yet h ogn a ot e ece i a ie nml I animal. live a in reached be t no can organ the d n a hsfna na question. ental fundam this h moe n o bt sds fa arcl: sti m this is cell: hair a of sides both on ent ovem m the H Versteegh: Versteegh: to m easure ho w m uch pow er w o uld be necessary to to necessary be uld o w er pow uch m w ho easure m to moeme i tansered i o a el tot hnica n ch te ctro le e an to in d rre sfe n tra is t en m ove m l a c steegh’s scale m odel study was used to help answeri help to used odelling, m was study analytical odel m and scale odelling steegh’s m ent elem finite the organ o f C o rti is very delicate. The m ovem ent is ent ovem m The delicate. very is rti o C f o organ the herefore a subject which is hard to investigate.” to hard is which subject a herefore ence. It is unclear how we m anage to do that and how how and that do to anage m we how unclear is It ence. eoe en al t d iae i atnin o this to attention his dicate de to able being Before pn, nalng os o tem i t dplrz a t a depolarize to in stream to ions g ablin en opens, rm h ne a r rnmitdt h ri. ec M brain. the to itted transm are ear inner the from electrical charge in the hair cell. In that way, the si the way, that In cell. hair the in charge electrical stereocilia, the hairs in the bundle on the surface the on bundle the in hairs the stereocilia, stud y en de d up as part of an article In N ature about about ature N In article an of part as up bundl d hair de the en of rest y the stud from stereocilia separate el (udt y e oy el) Sbeunl, e st he Subsequently, cells). sory sen ry dito (au cells This high selectivity a n d the capability o f handling f o capability the d n a selectivity high This e te yrdnmis f hs dl n tr n order in ater w in odel m this of ics hydrodynam the ied m ent sim ultaneous or not? A part from m easurem ents, ents, easurem m from part A not? or ultaneous sim ent m Frhr r, h cls h i er ombi th e in b m co ear r e n in the f o cells the ore, "Furtherm O tp h seecla a acu canal calcium a stereocilia, the f o top “On o w m a n y in te rn s c a n say th e y have have y e th say n a c s rn te in y n a m w o m ade a 12,000 tim es enlarged m odel of of odel m enlarged es tim he 12,000 York, a at New in ade m University Hudspeth in- Jim ? n Rockefeller an tio the a professor uring lic D b with u p can. re ternship tu a N Versteegh a to orstiaen C d te u trib n o c sounds. e. That That e. of hair hair of asmus ea as as ea gnals , Ver- , high media hani- tiny ove- Ver- Ver- In- gh: gh: - d u is t iny ng ng di- is r- e l

sitivity o f the cochlea's base, lo u d low frequency frequency low d u lo base, cochlea's the f o sitivity in but elaborate. new, and quite not detailed ere w - place first brane em the m basilar the to for the whole o f the cochlea.’’ the f o whole the for increases due to the sou nd volume, the local sensit local the volume, nd sou the to due increases influence o f the entire frequency range has been pro been has range frequency entire the f o influence in the cochlea decreases. A n d as high frequency sou frequency high as d n A decreases. cochlea the in o eut:i h moe n h aia mbra em m basilar the f o ent ovem m the if results: e som answ er contributes to the general understanding o f ho f o The noise. understanding in general speech the f to o enon contributes er enom ph answ the to approach h ae. ih rqec oe dmiih h se the inish dim tones frequency high d u o L apex. the sou of questions these to answers his says Versteegh distinguished.” are tones affect the whole o f the cochlea, all the way u way the all cochlea, the f o whole the affect tones i ns te estvt n h ccla s whole. a as cochlea the in sensitivity the inish dim successfully. successfully. e and ow neatos c ewen aiu tone various een betw r ccu o c the in interactions w propagate ho d n a lea soundwaves w ho part; selectivity ae ol as te ae h ccla omv, l move, to cochlea the f o base the cause only waves o tns apn o upes t rtns vice d n a tones er oth suppress to happen tones e Som h erpoess o a h aiu frequencies various w ho d an d n sou processes ear the es. e oul e ti rsac a a u a ntal e dam fun a as research this see ld u co ne O versa. rpgto, upeso ad neato - al rela all - interaction and suppression propagation, University In Rotterdam - a thesis he recently defen recently he thesis a - Rotterdam In University Senta lympani Senta the movement of animals. Although mastering in another area, he got interestedgot he area, another in mastering Although animals. of movement the University in New York. New in University Rockefeller the at Hudspeth the at Jim professor jumped with and internship an cells, do to opportunity hair especially hearing, of physiology sensory the in as finite element models are used to study for instance hydrodynamics related torelated hydrodynamics used tostudyinstance are for models element such as finite approaches physics where group, Zoology Experimental theoriented to moved broadly He systems. sensory for fascination a developing before ecology t aeign nvriy n Rsac Cne (U) H w He (WUR). Center Research and University Wageningen at biology in degrees master and bachelor his received Ph.D. Versteegh Corstiaen From biology to physics to biology From rin nc/ttihuli Sr/iin Cochlea

Ti rsac fcsd n h frequency the on focused research "This i l (Liciti ran a n. acoustic Int. meat meat us omtca / uia spiralis Lumina

ee mccplicus sm Reces T smmarize m sum “To Tympanic cavity Tympanic I II INF 9D14 9D14 II INF vcstilruli

ot /(tmic'ircuUir Post. tones canal The och- to p ded ded ivity ven ted ted nd- ow nd nd ne . Jteccssus . - n- s. Vestibule w

o. semicircular Lot. i* cochlear Fossa F is restituiti sur a aphcericus etblr /entslra Vestibular

ì

canal

? I OI V iV f IO iO n U A I ?n N

s novd in involved as

S O F N I Hearing processing

Inner hair cells

Tectorial membrane / Wikipedia Outer hair cells

The organ of Corti ^

Basilar fiber / / Spiral ganglion ▲ Cochlear nerve Stereocilla on a hair cell

These facts give a scientific explanation of fairly com - make it easier to optimize the study of the coil taken out mon, everyday observations regarding hearing situa- of the cochlea. “It is a matter of making a cross-section of tions. A beep-like noise in the background does not the cochlea in the right direction, so that you can see pa rt influence hearing dramatically, but a low frequency of the coil without the bone being crushed. During the background noise really makes it hard to understand whole procedure, the difference of potential - necessary nearby speech. to enable normal hearing - between the perilymfe (the liquid around the cochlea) and the endolymfe (the liquid The cellular level inside the cochlea) should remain intact. Now, with his Ph.D. on his resume, Versteegh has Both liquids, with the organ of Corti in between, should already turned back to his previous love, studying hear- therefore remain separated. I’ll try to make a prepara- ing at the cellular level. In fact he even turned back to tion from a mouse, although its cochlea is even smaller the location where he did his internship, with the group than that of a frog. But with mice, if the preparatio n of professor Hudspeth. “Out of two job offerings, this would be a succes, you can connect to a body of test one was the most appealing to me. I was of course work that is already laid down in literature.” flattered that professor Hudspeth wanted me back, but I also like the laboratory managament and laboratory From fundamental to applied culture here at Rockefeller University. You get a lot of This is obviously a lot of effort to establish the move- freedom to experiment here. That has its pro's and its ment of some tiny organ. “But if we want to know what con's, but for me the pro’s dominate.” has gone wrong in a person with damaged hearing - Versteegh works for five months in New York now and we do want to know that - we will first have to find and Is setting up his research for the years to come. out how hearing functions in a situation of healthy hear- “A few years ago, a postdoc in our lab made a working ing. And we don’t know that yet." preparation of the cochlea. You can take out one co il o f It is always easier to work at a cure from a position of in- the cochlea from a laboratory animal, the scala media. depth knowledge of the processes going on, than from If you do that properly, it is possible to keep it alive in our present knowledge position with gaps and black order to attain the ultimate goal: to study the microm e- boxes at some points. “It is important to know how the chanic motion taking place in different parts of the or- physiology of the ear works in order to be able to opti- gan of Corti. Until now, we really don’t know how these mize rehabilitation”, Versteegh concludes. movements take place. This being said - it is extrem ely He finds this type of research both challenging and difficult to do this.’’ exciting. “From the cochlea as a whole, down to the ste- At present Versteegh is busy making a preparation reocilia of the individual cell, there are various orders of chamber with a 3D-printer, which in a later phase will magnitude involved in this research. Furthermore, it asks a multidisciplinary approach with aspects of physics, medicine, biology and other fields. I also like the fun- damental nature of the research. Although there are no LC It is important to know how the physiology direct applications, eventually new findings can affect of the ear works in order to be able treatment. I’m looking forward to finding new knowledge offering clues for treatment." ■ to optimize rehabilitation. ^

*71 A iim nm rsv iMFnç i m on I n imf o r -i a