2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 1 Developmentof ComplexCurriculaforMolecularBionicsand InfobionicsProgramswithina consortial* framework** Consortiumleader PETER PAZMANY CATHOLIC UNIVERSITY Consortiummembers SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER The Project has beenrealisedwiththesupportof theEuropean Union and has beenco-financedbytheEuropean SocialFund*** **Molekuláris bionikaés InfobionikaSzakok tananyagának komplex fejlesztése konzorciumi keretben ***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg. PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS UNIVERSITY sote_logo.jpg dk_fejlec.gif INFOBLOKK 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 2 Peter PazmanyCatholicUniversity Facultyof InformationTechnology NEURAL INTERFACES AND PROSTHESES IMPLANTABLE HEARING AIDS www.itk.ppke.hu (Neurális interfészek és protézisek) (Beépíthető hallásjavító eszközök) RICHÁRD FIÁTH and GYÖRGY KARMOS LECTURE 7 NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 3 www.itk.ppke.hu Contents • Aims • The structureof theear • The structureof thecochlea • The mechanismof hearing • The auditorypathway • Hearing disorders • Cochlearmicrophony • Oto-acousticemission • Traditional hearing aids • Implantable hearing devices (IHD)– Boneanchoredhearingapparatus(BAHA) – Middleearimplantablehearingdevices(MEHID) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 4 www.itk.ppke.hu AIMS: Inthefollowingtwolecturesthestudentwillbecomefamiliarwithimplantablehearingdevicesusedforhearingdisorders.Afterashortintroductionaboutthebiologyofhearing,thepossibilitiesandtypesofauditoryprostheseswillbedetailed,focusingmainlyoncochlearimplants,butwewillshowothersolutions,rangingfromthemiddleearimplantablehearingdevicestomethodsinexperimentalstage(auditorybrainstemimplants,auditorymidbrainimplants). Thefirstlecturepresentsthestructureofthehumanearandcochlea,theauditorypathwayanddifferenthearingdisorders,togetherwithsomeinterestingphenomenarelatedtoauditorymechanisms(cochlearmicrophony,oto-acousticemission).Thisisfollowedbyashortreviewoftraditionalhearingaids.Finallyinthissection,thedetaileddescriptionoftheboneanchoredhearingapparatus(BAHA)andmiddleearimplantablehearingdevices(MEIHD)canberead. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 5 1.Outerear:Startsfromtheburr,throughtheearcanal(externalauditorycanal)untiltheeardrum(tympanicmembrane).Thefunctionoftheouterearistocollectsoundwaves.(greenonFigure1.) 2.Middleear:isanair-filledcavity,containingtheflexiblyjointedossicles(malleus,incus,stapes).Thestapesisattachedtotheovalwindow,thisistheconnectionpointbetweenthemiddleandinnerear.Lateralborder:eardrum,medialborder:osseouslabyrinth.Thefunctionofthemiddleearistheamplificationofthesoundandimpedancefitting.(redandblueonFigure1.) 3.Innerear:Containsthebalance(semicircularcanals)andhearing(cochlea)sensoryorgans.Consistsofabonypart(osseouslabyrinth,whichcanbeconsideredtobeatypeofcapsule)andamembranouspart(membranouslabyrinth)whichcontainsthereceptorcellsoftheorganofbalanceandhearing.(violetonFigure1.)Theauditoryandvestibularnervetransmitstheelectricsignalsfromtheinnereartothebrain. THE STRUCTURE OF THE HUMAN EAR NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 6 www.itk.ppke.hu http://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Anatomy_of_Human_Ear_with_Cochlear_Frequency_Mapping.svg/1000px-Anatomy_of_Human_Ear_with_Cochlear_Frequency_Mapping.svg.png Figure1. Anatomyof thehuman ear (commons.wikimedia.org) wikimedia_logo.bmp NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 7 Thecochleaisaspiral-shapedorgan(Figure1.,2.A),localizedintheanteriorpartoftheosseouslabyrinth(thebalancesensorysystemislocalizedposteriorly).Itsfunctionisthetransductionofmechanicwavesintoelectricsignals. IthasanosseouscapsuleandamembraneouspartthatcontainstheorganofCorti(Figure2.B,C)whichisthekeyofhearing.TheorganofCortiismadeupoftwotypesofhaircells(innerandouter,Figure2.D),supportingcells,basilarmembraneandtectorialmembrane.Themovementofthebasilarmembranemakesthestereociliaofthehaircellstouchthetectorialmembrane.Thisprocessresultsinthebendingofthestereocilia,thatopenscertainionchannels,andconsequentlydepolarizesthecells(Figure3.,4.).Thatisthepointof,wheremechanicalmovementisbeingtransformedintoelectricalactivitywhichistransmittedthroughtheauditorynervetothebrain. www.itk.ppke.hu THE STRUCTURE OF THE COCHLEA NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 8 •Theare approximately 15000 hair cells and 30000 nerve fibers in the cochlea. • The3500innerhaircellsareinnervatedbythe95%ofthenervefibers •The12000outerhaircellsareplacedinthreerowsandareinnervatedbytherest(5%)ofthenervefibers. • Therestingmembranepotentialofthehaircellsisaround-60mV. • The15%oftheionchannelsinthehaircellsareopen. •Receptorpotential:100nmdeflectionofthestereociliumcorrespondstothe90%oftheresponserange. •Normalstimulus:~±1odeflection(lessthanthediameterofthestereocilium) • Deflectionduetothermalnoise:3nm • Hearingthreshold:0.3nm www.itk.ppke.hu NUMBERS RELATED TO THE COCHLEA NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu cochlea.png 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 9 (commons.wikimedia.org) wikimedia_logo.bmp Figure 2. The cross section and the building blocks of the human cochlea A B C D NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 10 www.itk.ppke.hu THE MECHANISM OF HEARING 1. Soundwavescollectedbytheouterearreachtheeardrum,andcauseitsvibration.(mechanicwave,airconduction) 2. Mechanicwavesresultingfromthevibrationoftheeardrumaretransmittedtotheossicle-system(malleus,incus,stapes;boneconduction).Thefootplateofstapesisjoineddirectlytotheroundovalwindow,whichiscoveredbyaflexiblemembrane. 3. Viathefootplateofthestapesthemovementoftheossicle-chainleadstothevibrationoftheovalwindow,thusthemechanicalvibrationistransmittedtotheliquidoftheinnerear. 4. ThewavesintheliquidcausevibrationspreadinglongitudinallyonthebasalmembraneoftheCortiorgan(fluidconduction),thatmakesthestereociliaofhaircellstotouchthemembranatectoria.Thisresultsindepolarisationofthecells,thatinduceselectricpotentialinhearingnervefibres(mechano-electrictransduction). NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 11 www.itk.ppke.hu THE ACTIVITY OF HAIR CELLS Themostimportantpartofthehaircellsarethestereocilia(Figure3.).Whensoundwavesenterthecochlea,thestereociliatouchthetectorialmembranebecauseofthevibratingliquid,whichresultsinbendingofthese.Stereociliaareconnectedtogetherviatiplinks(Figure4.).Displacementofthestereociliatowardsthetallestproducesacelldepolarizationasioniccurrentflows(potassiumions)inthroughthemechanoelectric-transducerchannels.Theseionchannelscloseshortlyaftertheincreaseofcalciumionconcentration. Auditorynervesshowaspontaneousactivity,meaningthatthereisacontinuousdischargingwithagivenfrequency.Ifthehaircellsaredepolarized(benttowardsthetalleststereocilium),thisspontaneousspikeactivityisincreased(Figure4.).Incaseofhyperpolarization(stereociliaarebenttowardsthesmallestone)theeffectistheinverse:thefrequencyofthespontaneousactivityisdecreased(Figure4.). NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 12 www.itk.ppke.hu Figure3. The effectof themovementofthestereociliaonthespontaneousactivityoftheauditorynerve hair_cell_spont.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 13 www.itk.ppke.hu Figure4.Theworkingmechanismofthestereocilia:ifthestereociliaarebenttowardsthetallestone,theionchannelsopen,potassiumionsenterandthehaircelldepolarizes stereocilia.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 14 Tonotopyintheauditorysystembeginsinthecochlea.Differentregionsofthechord-likebasilarmembranevibrateatdifferentsinusoidalfrequencies,duetothemembrane’sdifferentwidthandtightnessatit’seachpoint.Becauseofthemechanicalpropertiesofthebasilarmembranewithinthesnail-shapedcochlea,highfrequencieswillproduceavibrationpeakneartheovalwindow,whereaslowfrequencieswillstimulatereceptorsneartheapexofthecochlea(Figure5.).Accordingtothefrequencyofthesinusoid,therewillbeapointonthebasilarmembrane,whichismostlysensitivetothesignalfrequency(so-calledcharacteristicfrequency).Themaximumamplitudeofthesignalwillbeexactlyatthepartofthemembranepointedoutbythecharacteristicfrequency.Thisisthepointwherethewavebecomesextincted,andtheresponseismaximal.Theauditorynervesthattransmitinformationfromdifferentregionsofthebasilarmembranethereforeencodefrequencytonotopically.Thistonotopyismaintainedincochlearnerveandinthehumancortexwheretheinformationisprocessed. TONOTOPY IN THE AUDITORY SYSTEM NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 15 www.itk.ppke.hu http://upload.wikimedia.org/wikipedia/commons/6/65/Uncoiled_cochlea_with_basilar_membrane.png (commons.wikimedia.org) wikimedia_logo.bmp Figure 5. Tonotopyin the uncoiled cochlea. High-pitched sounds are processed at the base while low-pitched sounds at the apex of the cochlea. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 16 Thetonotopydescribedbeforeisapassivetonotopy,butthereisalsoanactivemechanismoftheouterhaircells(OHC)whichampilifiesthesignaloriginatingfrompassivetonotopy.OnFigure6.theeffectoftheactivemechanismoftheouterhaircellsisshownincaseofatravellingwaveonthebasilarmembraneoftheguineapigcausedbyapuretonewith10kHzfrequency.Theouterhaircellsshiftthemaximaofthewavewithapproximately1octaveandOHCsalsoamplifytheamplitudeofthetravellingwavewitharound50dB.ThisactivemechanismisbecausetheOHCrespondstothedepolarizationbychanginglength.Ultrastructuralanalysisofcellplasmamembraneindicatesthatthiselectromotilitymaybebaseduponconformationalchangesofadensearrayofintegralmembraneproteins. TONOTOPY IN THE AUDITORY SYSTEM NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 17 www.itk.ppke.hu Figure6. The effectof theactivemechanismofouterhaircellcontractionontheamplitudeofthesoundwaves. OHC_active.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 18 FUNCTION OF THE ORGAN OF CORTI 1. Soundswavesmovethebasilarmembrane(BM)upanddown. 2. Mechano-transductionatOHCs:StereociliaoftheOHCs,implantedinthetectorialmembrane(TM),arebent,potassiumionsenterthecellwhichcausesdepolarization. 3. Electromotilityandreversetransduction:DepolarisationofthecellmembraneresultsinOHCcontractionwhichmagnifiesthemotion.Thisisanactivemechanism. 4. Mechano-transductionatinnerhaircells(IHC):DuetothetightcouplingofOHCswiththeBMandreticularlaminatheactivemechanismin(3.)feedsenergybackintotheorganofCorti.Innerhaircells(IHCs)areexcitedpossiblyviaTMactivationofIHCstereocilia. 5. IHC-auditorynervesynapseactivation:ThedepolarizedIHCsactivatetheIHC-auditorynervesynapseandanauditorymessageissenttothebrainviathetypeIafferentnerve. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 19 www.itk.ppke.hu THE AUDITORY SYSTEM AND PATHWAY Thesoundcomingfromtheouterworldenterstheear,thantravelsthroughtheearcanaltotheeardrum(airconductionintheouterear).Thepressureofthesoundmakestheeardrum(ortympanicmembrane)tovibrate,whichsetsthesmallbonesinthemiddleear(malleus,incus,stapes)intomotion.Thesoundisamplifiedandtravelsthroughthebonestotheovalwindow(boneconduction).Theovalwindowistheconnectionpointbetweenthemiddleearandtheinnerearorcochlea.Inthecochlea,thevibrationstravelviafluidconduction,causingthehaircellstomove,whichconvertthismovementintoelectricalimpulses.(Figure7.)Theseelectricalsignalsaretransmittedbythevestibulocochlearnervetothecochlearnucleiandsuperiorolivarycomplexofthebrainstemandtotheinferiorcolliculusofthemidbrain.Thenextstageofinformationprocessingisthemedialgeniculatebodyofthethalamus,wherethesignalsarerelayedtotheprimaryauditorycortex(Brodmannarea41,42),whichislocatedinthetemporallobeofthehumanbrain.(Figure8.) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 20 www.itk.ppke.hu auditory-system.img_assist_custom-599x365.png cochlear_hearalways_logo.gif Figure7.Thefirstpartoftheauditorypathwayfromtheeartothecochlea http://www.cochlear.com/ NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 21 www.itk.ppke.hu auditory-pathwway.img_assist_custom-366x471.png http://www.cochlear.com/ cochlear_hearalways_logo.gif Figure8.Thesecondpartoftheauditorypathwayfromthecochleatotheauditorycortex. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 22 www.itk.ppke.hu Figure9.Theauditorypathway Hearing_mechanics_cropped.jpg wikimedia_logo.bmp (commons.wikimedia.org) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 23 www.itk.ppke.hu QUANTIFICATION OF HEARING LOSS Theseverityofahearingimpairmentisrankedaccordingtotheloudnessasoundmustbebeforebeingdetectedbyanindividual.Itismeasuredindecibels(dB). • Mild: • for adults: between 27 and 40 dB • for children: between 20 and 40 dB • Moderate: between 41 and 55 dB • Moderately severe: between 56 and 70 dB • Severe: between 71 and 90 dB • Profound: 90 dB or greater These intervals are displayed on the example of an audiogram. (Figure11.) Thedecibelscaleislogarithmic,whichmeansthata10dBdifferencebetweentwosoundsmeansatenfolddifferenceintheloudness,20dBmeans100x,30dBmeans1000xdifferenceintheloudnessbetweenthetwosounds. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 24 www.itk.ppke.hu HEARING DISORDERS Conductivehearingloss-Anyproblemintheouterormiddleearthatpreventssoundfrombeingconductedproperlyisknownasaconductivehearingloss.Itcanbecausedbyexcessiveearwax,earinfections,tympanicmembraneperforation,otosclerosisortumours.Thedegreeofconductivehearinglossismildormoderateandmaybehelpedwithmedication,surgery,hearingaidsormiddleearimplants.(Figure10.A) Sensorineuralhearingloss-Sensorineuralhearinglossresultsfrommissingordamagedsensorycells(haircells)inthecochleaandcanbemild,moderate,severeorprofound.Mildtoseveresensorineuralhearinglosscanoftenbehelpedwithtraditionalhearingaidsormiddleearimplants.Cochlearimplantsareoftenasolutionforsevereorprofoundhearingloss.Partialdeafnessmeansthatthesensorineuralhearinglossisonlyinthehighfrequencies:hereacombinedelectricandacousticstimulation,theEAScanhelp.Sensorineuralhearinglossmaybecongenitaloracquired.(Figure10.B) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 25 www.itk.ppke.hu HEARING DISORDERS Mixedhearingloss-Amixedhearinglossisacombinationofbothconductiveandsensorineuralhearingloss.Theinner,outerandmiddleearisdamagedatthesametimeforthesamereasonorfordifferentreasons.Medication,surgery,hearingaids,middleearimplantsandcochlearimplantscanbetreatmentoptions.(Figure10.C) Neuralhearingloss–Resultsfromthedamageoftheauditorynerveorotherbrainstructuresrelatedtotheauditorypathway.Neuralhearinglossisusuallypermanentandprofound.Experimentalprosthesesliketheauditorybrainstemimplant,placedintothecochlearnucleiortheauditorymidbrainimplant,placedintotheinferiorcolliculusmaybeapossibilityfortreatment.(Figure10.D) UnilateralProfoundSensorineuralHearingLoss(SingleSidedDeafness,SSD)–Meanssensorineuraldeafnessinoneear,whiletheotherearhasgoodhearing.Itisusuallysevereandpermanent. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 26 www.itk.ppke.hu Figure10.Damagedstructuresindifferenttypesofhearingdisorders.A–Conductivehearingloss,B–Sensorineuralhearingloss,C–Mixedhearingloss,D–Neuralhearingloss hearing_disorders.png (commons.wikimedia.org) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 27 www.itk.ppke.hu AUDIOGRAM Hearingsensitivityvariesaccordingtothefrequencyofsounds.Totakethisintoaccount,hearingsensitivitycanbemeasuredforarangeoffrequenciesandplottedonanaudiogram.Onthex-axisofanaudiogramarethefrequenciesrangingfromabout125Hzto8kHz(or16kHz),usuallyonalogarithmicscale.Ontheverticalaxistheloudnessofthesoundsisrepresented,measuredindecibelsrangingfrom-10dBto120dB.(Figure11.) Anaudiogramcanbeobtainedusingabehavioralhearingtestcalledaudiometry.Thismeanspresentingdifferenttonesataspecificfrequencyandloudness(intensity).Whenthepersonhearsthesoundtheyraisetheirhandorpressabuttonsothatthetesterknowsthattheyhaveheardit.Thelowestintensitysoundtheycanhearisrecorded.Withnormalhearingallfrequenciesareheardatlowintensities(Figure12.A),incaseofdeafnessnosignofsoundhearingispresent,orjustathighintensitiesabove80dB(Figure12.B).Partialdeafnessaffectsonlythehighfrequencies,peoplewhosufferfrompartialdeafnessneedhigherintensitiestohearsoundsabove4000Hz. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 28 www.itk.ppke.hu AUDIOGRAM.jpg Figure11.Theaudiogram.Theclassificationofthehearinglossisshownontherightsideofthefigure.Theloudnessofsomesoundsourceswithdifferentfrequenciesaredisplayedtoo(littlepictures). http://www.cochlear.com/ cochlear_hearalways_logo.gif NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 29 www.itk.ppke.hu audiogram.png Figure12. A -The audiogram of a normal hearing B –The audiogram of deafness wikimedia_logo.bmp (commons.wikimedia.org) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 30 www.itk.ppke.hu Togenerateapsychoacousticaltuningcurve,anarbitraryfrequencyischosen,andtheamplitudeisloweredsuchthatthesubjectcanbarelydetectit(~2dBabovethreshold).Thisprobetonewillbeintermittent.Then,themaskertoneispresentedatadifferentfrequency,andtheamplitudeisincreasedashighaspossiblesuchthatthesubjectcanstilldetecttheprobetone.Thisprocessisrepeatedformultiplefrequencies,andthelinegraphofthetuningcurveisderived.InFigure13.weseetwopsychoacousticaltuningcurves-oneforanormalcochleaandoneforacochleawithdamagedouterhaircells.Noticethatthedamagedcochleaisbothlesssensitive(thelineislower)andlessselective(thecurveisnotsharp).Thus,torestorehearinginsomeonewithouterhaircelldamage,simpleamplificationisnotenough,sincethatraisesinaudible,indistinguishablesoundstothelevelofaudible,indistinguishablesounds.Theselectivityproblemneedstobesolvedtohaveusefulhearing. TUNING CURVE NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 9/14/2011. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 31 www.itk.ppke.hu http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Psychoacoustical_tuning_curves.svg/1000px-Psychoacoustical_tuning_curves.svg.png (commons.wikimedia.org) Figure13. The tuningcurveof a normalcochlea(blue) and of a cochleawithdamagedouterhaircells(red). wikimedia_logo.bmp NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 32 www.itk.ppke.hu HEARING LOSS AND AGE The age at which hearing loss occurs is crucial for the acquisition of a spoken language: •Pre-lingualdeafness:ahearingimpairmentthatissustainedpriortotheacquisitionoflanguage,whichcanoccurasaresultofacongenitalconditionorthroughhearinglossinearlyinfancy. •Post-lingualdeafness:ahearingimpairmentthatissustainedaftertheacquisitionoflanguage,whichcanoccurasaresultofdisease,trauma,orasaside-effectofamedicine.Post-lingualdeafnessisfarmorecommonthanpre-lingualdeafness. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 33 www.itk.ppke.hu OBJECTIVE TESTS Audiometryisasubjectivetest,itneedsaresponsefromthetheexaminedpatient.Howevertherearealsoobjectivetests,whichdonotneedanyresponsefromthesubjectsanditcanbeperformedinsleeporinawakestate. • AuditoryBrainstemResponseTesting(ABR):Itisused,whensubjectivetestscannotbeperformed,forexampleininfants.Clickstimuliaregiventhroughearphonesandtheelectricalresponsesarerecordedfromtheauditorynerveandbrainstem.Thismethodcanprovidereliablethresholdinformationforfrequenciesupto2kHz. • TransientOtoacousticEmission(TOAE):Itisaquickmethod,totestifthereisanycochleardamage(e.g.lossofouterhaircells).Itisoftenusedtotestthehearingconditionofneonatals.AboutOtoacousticemissionyoucanreadmoreafewslideslater. • ImmittanceAudiometry(tympanometry):Itisadiagnosticmethod,totestifthereisanymiddleearrelatedhearingdisorderpresent.Thecomplianceandpressureofthemiddleearareassessed. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 34 www.itk.ppke.hu COCHLEAR MICROPHONIC Cochlearmicrophonic(CM)isanelectricpotentialgeneratedbythecochlearhaircells(mainlyouterhaircells)andcanberecordedwithintra-tympanicandextra-tympanicelectrocochleography(ECochG)inhumansandinexperimentalanimals(e.g.guineapig).Incaseofextra-tympanicECochGathinneedleelectrodeisplacedthroughthetympanicmembraneontothepromontory,neartheroundwindowandthecochlearpotentialsarerecorded.CMcanalsoobtainedfromsurfacerecordings.Thecochlearmicrophonicisoriginatingprimarilyfromthebasalportionsofthecochleaanditcloselyresemblesthesoundstimulus,itisareflectionofthealternatingcomponent. CMhasalimitedclinicaluse,itcanbeusedintheidentificationofauditoryneuropathy,wheretheauditorynervefibersaredamagedbecauseofdemyelination,axonallossorlesion.Howevertheouterhaircellintegrityispreserved,whichcanbeexaminedbyCM. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 35 www.itk.ppke.hu OTOACOUSTIC EMISSION (OAE) Theotoacousticemission(OAE)isalow-intensitysoundwhichisgeneratedfromwithintheinnerear,mostlybythecochlearouterhaircells,astheyexpandandcontract.OAEsdisappearaftertheinnerearhasbeendamaged,sotheycanbeusedtodeterminethecochlearstatusandthehaircellfunction.Otoacousticemissionhasagreatclinicalimportance,becauseitisthebasisofasimple,non-invasivetestforhearingdisordersinneonates,infantsandinchildrenwhoaretooyoungtocooperateinconventionalhearingtests.BecausehearingtestswithOAEsdonotrequireanybehavioralresponse,itcanbeperformedalsoonsleepingoroncomatosepatients.SpontaneousOAEsarepresentinonly40-50%ofthepeople,whohavenormalhearing,andcanbeconsideredasasignofcochlearhealth,buttheabsenceofspontaneousOAEsisnotnecessarilyasignofabnormality. TherearealsoresearchestoutilizeOAEsforbiometricidentification,butstillseveraldifficultieshavetobesolveduntilitcanbecameuseableintheeverydaylife. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 36 www.itk.ppke.hu OTOACOUSTIC EMISSION (OAE) There are4 types of otoacousticemissions, one spontaneous and three evoked: • Spontaneousotoacousticemissions(SOAEs)-Soundsemittedwithoutanexternalstimulus(i.e.spontaneously). • Transientotoacousticemissions(TOAEs)ortransientevokedotoacousticemissions(TEOAEs)-Soundsemittedinresponsetoanacousticstimuliofveryshortduration(e.g.clicksortone-bursts). • Distortionproductotoacousticemissions(DPOAEs)-Soundsemittedinresponseto2simultaneoustonesofdifferentfrequencies. • Sustained-frequencyotoacousticemissions(SFOAEs)-Soundsemittedinresponsetoacontinuoustone. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 37 www.itk.ppke.hu TRADITIONAL HEARING AIDS Traditionalhearingaidsaredesignedtoamplifythesoundinfrequencyranges,wherethehearinglossisthegreatest.Usuallyitbuildsupfromamicrophone,anamplifier,aprocessor,aspeakerandabattery(Figure14.).Thesoundisreceivedthroughamicrophone,whichtransmitsittotheamplifierinelectricfrom.Theamplifierincreasesthepowerofthesignalsandthensendsthemtotheprocessorformodulation.Finallythesignalgetstothespeaker,wheretheamplifiedandmodulatedsoundenterstheearcanal.Hearingaidscanbeanalogordigital.Programmablehearingaidsalsomakeitpossibletochangethesettingsofthehearingaidaccordingtodifferentlisteningenviroments.Digitalcircuitrymakesprogrammingmoreflexible,forexampleahearingaidcanbeprogrammedtoamplifysomefrequenciesmorethanothers. Hearingaidsarethemosteffectiveincaseofconductivehearinglosswithmildandmoderatelevel,orincaseofsensorineuralhearingloss,whereaproportionoftheouterhaircellsisdamaged. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 38 www.itk.ppke.hu Figure14. Schematic of the traditional hearing aid trad_hearing_eid.png NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 39 • Behind-the-ear(BTE)hearingaid:Ahardplasticcase,wheretheelectronicstakeplace,iswornbehindthepinna.Thisisconnectedwithatubetoaplasticearmold,thatfitsintotheearcanal.Thesoundisroutedfromthecasetotheearmoldviathetube.BTEhearingaidisusedbypeopleofallagesformildtoprofoundhearingloss.AsubtypeoftheBTEhearingaidistheopen-fithearingaidor„mini”BTE:itfitsbehindtheearcompletelyandanarrowtubeisinsertedintotheearcanal.Thecanalremainsopen,whichallowssoundtoentertheearwithoutbeingamplified.Thisisadvantageousforpeoplewithhighfrequencyhearingloss. • In-the-ear(ITE)hearingaid:Itfitscompletelyinsidetheouterearbowlandisusedformildtoseverehearingloss. • Canalhearingaids:Itfitsintotheearcanal.Thein-the-canal(ITC)hearingaidismadetofitthesizeandshapeofaperson’searcanal.Acompletely-in-canal(CIC)hearingaidisnearlyhiddenintheearcanal.Bothtypesareusedformildtomoderatelyseverehearingloss. www.itk.ppke.hu TYPES OF TRADITIONAL HEARING AIDS (Figure15.) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 40 www.itk.ppke.hu Figure15. Styles of traditional hearing aids and examplesof a BTE and a CIC hearing aid HearingAidTypes.jpg hearing aid.jpg Hearing_aid_cic.jpg wikimedia_logo.bmp (commons.wikimedia.org) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 41 www.itk.ppke.hu TRADITIONAL HEARING AIDS Other types: • Invisible-in-canal hearing aids (IIC) –Placed deep in the ear canal • Receiver-in-the-Canal/Ear (RIC/RITE) –Speaker placed inside the ear canal • Extended wear hearing aids –Continuously worn, invisible Technological developments: • Wireless hearing aids and FM listening systems • Directional microphones to improve the speech recognition in noise • Telecoilsusedwithtelephones,FMsystemsandinductionloopsystems(hearingloops)-Atelecoilisasmallmagneticcoilthatallowsuserstoreceivesoundthroughthecircuitryofthehearingaid.Ithelpspeoplehearinpublicfacilitiesthathaveinstalledinductionloopsystems. • Direct Audio Input (DAI) –direct connection to external audio sources NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 42 www.itk.ppke.hu IMPLANTABLE HEARING DEVICES (IHD) • Bone anchored hearing apparatus (BAHA) • Middle ear implantable hearing devices (MEIHD) • Cochlear implants (CI) • Electric Acoustic Stimulation(EAS) • Auditory brainstem implants (ABI) • Auditory midbrain implants (AMI) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 43 INTRODUCTIONTOIHDs Auditoryprosthesesareoneofthemostsuccessfulneuralprosthesesthatrestorehumansensoryfunction.Theyhavebeenusedtopartiallyrestorehearinginmorethan60000hearing-imparedpeopleworldwide.ThereareseveralsolutionsofIHDsaccordingtotheplaceofthedamageintheauditorysystemortypeofhearingloss(Figure16.).Themostsuccessfuloneisthecochlearimplantwhichwillbedetailedinthenextlecture.Whenconductivehearinglossispresent,aboneconductinghearingdeviceliketheBAHAseekstorestorehearingbyvibratoryconductionthroughtheskulltotheinnerear.SensoryhearingimpairmentisalsotreatedbyMEIHDswhichamplificatethesoundsignalsthroughimplantedtransducerswichcanbeeitherpiezoelectriccrystalsorelectromagnetictransducers.TheVibrantSoundbridgeSystemproducedbyMed-Elwillbedemonstratedindetailsinthissection.Devicesinexperimentalphaseliketheauditorybrainstemimplant(ABI)andauditorymidbrainimplant(AMI)willbediscussedalsointhenextlecture. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 44 www.itk.ppke.hu Figure16.Targets(red)ofdifferenttypesofhearingaids(blue).Onthehorizontalarrowsthemethodofsignalgenerationoftherespectivehearingaidispresented.Nexttotheverticalarrows,thewaysoftransmittingthesound-signalsoriginatingfromtheoutsideworldareshown. hearing_aids.png EAS –Electric Acoustic Stimulation BAHA -Bone anchored hearing apparatus MEIHD -Middle ear implantable hearing devices ABI -Auditory brainstem implants AMI -Auditory midbrain implants NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 45 www.itk.ppke.hu BONE ANCHORED HEARING APPARATUS(BAHA) TheBAHAisahearingaidbasedonboneconduction:ittransmitssoundbydirectconductionthroughbonetotheinnerear,bypassingtheouterearandmiddleear.Itisusedbypeoplewithconductive,mixedorunilateralhearingloss(singlesideddeafness).Asoundprocessorisfixedthroughanabutmenttoasurgicallyimplantedtitaniumimplant,whichisembeddedintotheskullofthepatient.Theabutmentisexposedoutsidetheskin.Thetitaniumfixturehastobondwiththebone.Thisprocessiscalledosseointegrationandlastsforafewmonths.AfterosseointegrationtheBAHAcanbeused.Duringworking,thesystemvibratestheskullandtheinnerear,whichstimulatesthecochlearnerve.Twocompanieshavesolutionsusingboneconduction:Cochlear(BahaSystem,Figure17-19.)andOticonMedical(Ponto,PontoPro).CochlearregisteredtheacronymBahaasatrademark.BAHAhassomedrawbacks:theopenwoundmeansariskofinfection,soadailycareisrequired;batterieslastonlyfor6to14days.SeveralaccessoriesareavailableforBAHA:telecoil,audioadapter(toconnecttoexternalaudiosources)andFMreceiver. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 46 www.itk.ppke.hu bahasystem_med.jpg Figure17. Working mechanism of a BAHA 1. A sound processor picks up sound vibrations. 2.Anabutmentisattachedtothesoundprocessorandtheimplant.Theabutmenttransfersthesoundvibrationsfromtheprocessortotheimplant. 3.Asmalltitaniumimplantisplacedinthebonebehindtheearwhereitfuseswiththelivingbone(osseointegration).Theimplanttransfersthesoundvibrationsthroughtheskulltothefunctioningcochlea. http://www.cochlear.com/ cochlear_hearalways_logo.gif NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 47 www.itk.ppke.hu bahaprocessor_med_1.jpg how_works_med_BP100_0.jpg baha_diagram_lrg http://www.cochlear.com/ cochlear_hearalways_logo.gif baha-illus_med_NEW.jpg Figure18. Parts of the Cochlear Baha system NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 48 www.itk.ppke.hu bone_conduction_med_0.jpg single-side_med.jpg Figure19. Left –Direct bone conduction: 1. Sound waves arereceived by Bahasound processor 2. Sound waves bypass middle ear function and are delivered directly to the working cochlea in both ears Right –Single Sided Deafness 1. Sound waves arereceived by the Bahasound processor 2. Sound waves travel by bone conduction to the functioning cochlea on the opposite side 3. Sound is received by functioning cochlea http://www.cochlear.com/ cochlear_hearalways_logo.gif NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 49 www.itk.ppke.hu MIDDLE EAR IMPLANTABLE HEARING DEVICES MEIHDsweredevelopedtotreatconductiveorsensorineuralhearinglosswithadegreefrommildtosevere.MEIHDscanbepartially-implantedortotally-implanted.Totally-implantedsolutions,wherethedeviceiscompletelyconcealedinthebody,arefullyfunctioningalsoduringswimmingorbathing,andthereisnoocclusioneffectpresent(Occlusioneffect:whenanobjectfillstheearcanal,andthepersonperceives"hollow"or"booming"echo-likesoundsoftheirownvoice.Itismostlyexperiencedincaseoftraditionalhearingaids).MEIHDsdirectlystimulatetheossiclesinthemiddleear,andbecausethesensorandthedriverisuncoupled,thefeedback(whichisanotherannoyingeffectsofconventionalaids)isalmostcompletelyeliminated.Thesedeviceshavetofulfilsomeimportantrequirements:thetransducermustbeattachedtothetympanicmembrane,thelongprocessoftheincus,ortheheadofthestapes,becauseotherwise,thetransmittedforceisreduced.Thebatterylifemustbesufficienttoavoidfrequentreplacementsrequiringreoperation.SomemiddleearimplantsarealsocompatiblewithMRI. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 50 www.itk.ppke.hu MIDDLE EAR IMPLANTABLE HEARING DEVICES Middleeardevicescanbeclassifiedintotwogroups:therearepiezoelectricandelectromagneticsolutions. Piezoelectricdevicesoperatebypassinganelectriccurrentintoapiezoceramiccrystal,whichchangesitsvolume(bydeformationorbending).Thisdeformationprovidesthemechanicalenergytostimulatetheossicularchainorinnerear,itproducesavibratorysignal.Thepoweroutputisdirectlyrelatedtothesizeofthecrystal. Electromagnetichearingdevicesfunctionbypassinganelectriccurrentintoacoil,whichcreatesafluctuatingmagneticfield(correspondingtotheacousticinput).Thiscausesasmallmagnet(samariumcobaltorneodymiumironboron),whichisattachedtothevibratorystructuresofthemiddleear,tovibrate.Thisvibration,inturn,causesthemovementofthesestructuresresultinginthesensationofhearing.Thecoilmaybeseparatefromthemagnetorintegratedwithit.Thecoilandmagnetmustbeclose,becausethepowerisdecreasedbythesquareofthedistancebetweenthem. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 51 SOLUTIONS FOR MEIHDs www.itk.ppke.hu Name Manufacturer Transducer Implantable TICA (Totally Integrated Cochlear Amplifier) Cochlear(device developed by Implex AG) Piezoelectric Fully Envoy Esteem System Envoy Medical (originally St. CroixMedical) Piezoelectric Fully MET (Middle Ear Transducer) OtologicsLLC Electromagnetic Semi Carina MET Otologics LLC Electromagnetic Fully Vibrant Soundbridge Med-El(device developed by Symphonix Devices) Electromagnetic Semi Direct System Soundtec Electromagnetic Semi MAXUM System Ototronix Electromagnetic Semi NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 52 www.itk.ppke.hu THE VIBRANT SOUNDBRIDGE SYSTEM ThismiddleearhearingdevicewasdevelopedbySymphonixDevices.ThetechnologywaslaterpurchasedbyMed-El.ItwasthefirstFDA-approvedimplantableMEIHD(2000)andgotalsotheEuropeanCE-mark(1998).Nowitisimplantedworldwide.VibrantSoundbridgeisasemi-implantabledevicewithanelectromagnetictransducerandconsistsofanexternalsoundprocessorandamplifier(Amadé),andaninternalvibratingossicularprosthesis(VORP),whichissurgicallyimplanted.SoundpassesintoamicrophoneonthepostauricularaudioprocessorandistransmittedthroughtheskintothereceiverontheVORP.TheVORP,whichisimplantedpostauricularly,conductsthesoundtoamagnetsurroundedbyacoil,calledthefloatingmasstransducer(FMT).Thetransduceriscrimpedaroundthelongprocessoftheincusbyatitaniumclip.Vibrationofthedeviceistransmittedtotheossicles,therebydeliveringstimulitothemiddleand,subsequently,totheinnerear.(Figure20.) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 53 www.itk.ppke.hu THE VIBRANT SOUNDBRIDGE SYSTEM –FEATURES AND BENEFITS • improved hearing quality • improved speech understanding(particularly in noisy environment) • ear canal remains completely open(no occlusion effect) • no feedback or irritating whistling • wind-noise reduction • speechand noisemanagementwith the Amadé audio processor • high wearing comfort • reliable and flexible • suitable for children NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 54 www.itk.ppke.hu Figure20. Parts of the VibrantSoundbridgeMEIHD(Med-El, Austria) crosssectionzoom Audio Processor Receiver(VORP) Conductor lead FloatingMass Transducer (FMT) http://www.medel.com/ medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 55 VIBRANT SOUNDBRIDGE -TERMINOLOGY • AP -Audio Processor(Amadé) Theexternalsignalprocessorcontainingmicrophone,batteryandelectronics.Itisattachedtothepatient’sheadwithamagnetandcanbeworndiscreetlyunderneaththehair.Threedifferentprogramsareavailable,whichcanbeadaptedtofitpersonalpreferences.(Figure21.) • VORP -Vibrating OssicularProsthesis Thecompleteimplantdevice,includingthereceivercoil,attachmentmagnet,receiverelectronicsandFMT.Itisplacedunderneaththeskinandtheattachmentmagnetholdstheaudioprocessorovertheimplant.(Figure22.) • FMT -Floating Mass Transducer Theelectromagnetictransducerthatgeneratesthevibratorymotion.Itconductsawidefrequencyrange(upto8,000Hz),whichisparticularlyrelevantforlisteningtoorplayingmusic.Thistinymagnetconsistsofjustfivecomponents.Itcanbeattachedtotheincus,totheroundortotheovalwindow.(Figure23.andFigure24.) NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 56 www.itk.ppke.hu Figure21. The Amadé Audio Processor http://www.medel.com/ medel_logo.jpg vibrant_processor.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 57 www.itk.ppke.hu Figure22. The Vibrating OssicularProsthesis (VORP) vorp1 Demodulator Receiver coil Magnet Silicone Floating Mass Transducer http://www.medel.com/ medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 58 www.itk.ppke.hu FMT Figure23. The Floating Mass Transducer(FMT) -The FMT isattachedto the long processof the incus witha Titaniumclip. cola-vorp-fondo blanco Titanium clip 2 mm http://www.medel.com/ vibrant_fmt.jpg medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 59 www.itk.ppke.hu Figure24.TheFMTreproducesandamplifiesthenaturalmovementoftheossicularchain.TheFMTshouldbeinclosecontactandparalleltothestapes. http://www.medel.com/ medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 60 www.itk.ppke.hu THE VIBRANT SOUNDBRIDGE SYSTEM –WORKING MECHANISM 1. Sounds are picked up by the microphone of the audio processor. 2. The audio processor converts environmental sounds into electrical signals. 3. The electrical signals are transmitted across the skin to the implanted part. 4. The implant relays the signal down to the FMT. 5. The FMT converts the signal into mechanical vibrations that directlystimulate a middle ear structure (e.g., the ossicularchain) causing it to vibrate. 6. These vibrations then conduct sound to the inner ear wherethey are passed on tothe brain and are perceived as sound. NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS www.itk.ppke.hu 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 61 THE FUTURE PROSPECTS OF HEARING AIDS • Totally Implant system • Perfectly hide • External control using wireless communication • More convenient • Miniaturized • High-performance • Will be popularized in near future NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 62 www.itk.ppke.hu WEBPAGES OF COMPANIES RELATED TO IMPLANTABLE HEARING AIDS • www.oticonmedical.com • www.cochlear.com • www.medel.com • www.advancedbionics.com • www.envoymedical.com • www.otologics.com • www.ototronix.com • www.soundtecinc.com cochlear_hearalways_logo.gif oticon_medical_cmyk_p.jpg ABlogo_RGB.gif advancedBionics-logo.gif MEDEL_logo.gif otologics_company_logo.php.gif envoymed_logo_blue_tm_800.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 63 www.itk.ppke.hu LINKS RELATED TO HEARING AIDS Traditional hearing aids: http://www.nidcd.nih.gov/health/hearing/hearingaid.asp http://www.hearingaids1000.com/index.shtml BAHA: http://www.entkent.com/baha.php MEIHD: http://emedicine.medscape.com/article/860444-overview http://www.middleearimplants.com/ NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS neural_prost.jpg 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 64 www.itk.ppke.hu RECOMMENDED LITERATURE • Cochlear implants: Auditory Prostheses and Electric Hearing; Fang-Gang Zeng, Arthur N. Popper, Richard R. Fay; 2004; Springer • Handbook of Neuroprosthetic Methods; Warren E. Finn, Peter G. LoPresti; 2003, CRC Press • Neuroprosthetics: Theory and Practice; Kenneth W. Horch, Gurpreet S. Dhillon; 2004; World Scientific Publishing • Cochlear And Brainstem Implants (Advances in Oto-Rhino-Laryngology); A.R. Moller; 2006; Karger • Neural Prostheses for Restoration of Sensory and Motor Function; John K. Chapin, Karen A. Moxon; 2000; CRC Press • More than 500 books related toimplantablehearingaidsimplants on www.amazon.com neuropr2.jpg cochl_brainstem.jpg cochlearimplants.jpg neuropr.jpg NEURAL INTERFACES AND PROSTHESES:IMPLANTABLE HEARING AIDS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 65 www.itk.ppke.hu REVIEW QUESTIONS • Whatarethethreemain partsof thehuman ear? • Whatis thestructureand workingmechanismof thecochlea? • Howdoyoumakea tuningcurve? • What are the main processing stations in the auditory pathway? • What type of hearing disorders do you know? • What is the audiogram good for? • How is the phenomenon of otoacoustic emission generated? • How are traditional hearing aids helping people with hearing impairment? • What are the main types of implantable hearing devices? • What is the working mechanism of a BAHA? What are its main parts? • How can be the MEIHDs grouped? What parts build up the Vibrant Soundbridge system? Can you mention another MEIHD solutions?