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 bionika és Infobionika Szakok 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 COCHLEAR IMPLANTS www.itk.ppke.hu (Neurális interfészek és protézisek) (Cochleárisimplantátumok) RICHÁRD FIÁTH and GYÖRGY KARMOS LECTURE 8 NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 3 www.itk.ppke.hu CONTENTS • Aims • Implantable hearing devices (IHD)– Cochlear implants (CI)• History of CIs • Parts of CIs • Electrical stimulation strategies • Speech performance • Commercially available CIs – Electric Acoustic Stimulation (EAS) – Auditorybrainstem implants (ABI) – Auditorymidbrain implants (AMI) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 4 www.itk.ppke.hu AIMS: Inthepreviouslecturewepresentedthestructureofthehumanearandcochlea,theauditorypathwayanddifferenthearingdisorders.Thiswasfollowedbyashortreviewoftraditionalhearingaids.Finally,thedetaileddescriptionoftheboneanchoredhearingapparatus(BAHA)andmiddleearimplantablehearingdevices(MEIHD)couldberead. Thislectureisaboutthecochlearimplant(CI)andcontainsthebasicbuild-uppartsofsuchaprosthesis,themainspeechprocessingorelectricalstimulationstrategiesoftheelectrodesplacedinthecochlea,theavaiblesolutionsofthefourcompaniesproducingCIsandthedetailedviewofthesesystems.Afterthese,theefficiencyofimplantablehearingdeviceswillbediscussed,concentratingontherelationshipbetweentheunderstandingofspeechandthenumberofelectrodesortheinsertiondepthandtheadvantagesoftheimplantationinchildhood.Finallytwoexperimentaldevices,theauditorybrainstemimplant(ABI)andtheauditorymidbrainimplant(AMI)willbedemonstrated. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 5 www.itk.ppke.hu IMPLANTABLE HEARING DEVICES (IHC) • 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 6 INTRODUCTION TO IHDs Auditoryprosthesesareoneofthemostsuccessfulneuralprosthesesthatrestorehumansensoryfunction.Theyhavebeenusedtopartiallyrestorehearinginmorethan60000hearing-impairedpeopleworldwide.ThereareseveralsolutionsofIHDsaccordingtotheplaceofthedamageintheauditorysystemortypeofhearingloss(Figure1.).Themostsuccessfuloneisthecochlearimplant(CI),demonstratedinthislectureindetail.CIsuseelectricalstimulationwithelectrodesplacedinthecochleatoproducehearingsensations.Thedeviceistotallyimplantedinthepatients.Whenconductivehearinglossispresent,aboneconductinghearingdeviceliketheBAHArestoreshearingbyvibratoryconductionthroughtheskulltotheinnerear.SensoryhearingimpairmentisalsotreatedbyMEIHDswhichamplifiesthesoundsignalsthroughimplantedtransducerswhichcanbeeitherpiezoelectriccrystalsorelectromagnetictransducers.Devicesinexperimentalphaseliketheauditorybrainstemimplant(ABI)andauditorymidbrainimplant(AMI)willbediscussedalsointhislecture. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 7 www.itk.ppke.hu Figure 1.Targets (red) of different types of hearing aids (blue). On the horizontal arrows the method of signal generation of the respective hearing aid is presented. Next to the vertical arrows, the ways of transmitting the sound-signals originating from the outside world are shown. 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:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 8 www.itk.ppke.hu COCHLEAR IMPLANTS (CI) -INTRODUCTION Patientswithaprofound,bilateral,sensorineuralhearinglossorwithauditoryneuropathyarecandidatesofcochlearimplants.Thepatientselectioncriteriaisalessthan50%open-setsentencerecognitionwithproperlyfittedhearingaids(suprathresholdspeech-basedcriteria).Over120000peoplewereimplantedwithCIs,providingrestoredorpartialhearing(2008).Inchildren,earlyimplantationpromotesthematurationprocessintheauditorycorticesandnormallanguagedevelopment.PostlinguallydeafenedCIusersgothroughalearningoradaptationprocessfromafewmonthstoaslongasafewyears,duringwhichtheirspeechperformancecontinuestogetbetter. Thegoalofthesedevicesistosafelyuseelectricstimulationtoprovideorrestorefunctionalhearingintotallydeafenedpersons.Anelectrodearrayisinsertedintothescalatympanytodirectlystimulatediscretesectorsofauditorynerve,takingadvantageofthetonotopicorganizationofthecochlea(Thefrequency-to-structuremapiscalledtonotopicorganization.).ThecostofCIsrangesfrom$40000to$75000(device,surgeryandhospitalcosts). NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 9 www.itk.ppke.hu HISTORY OF COCHLEAR IMPLANTS • XVIIIthcentury-Firstdocumentedattempttoprovideelectricalstimulationdirectlytotheauditorysystem:AlessandroVoltainsertedmetalrodsattachedtoanactivecircuitintohisears. • 1950s-Firstsuccessfulelectricalstimulationofhearingnervesbyinsertinganelectrodeinadeafsubject'sinnerear(DjournoandEyries,1957).Perceivingtherhythmofspeechandassistanceinlipreading. • 1970s-Firstwide-spreadclinicalapplication:single-channeldevicesthatsentcodedinformationtoonlyoneelectrodesite.Providedspeechandsoundawareness,enhancedlipreadingability,butnoauditory-onlyspeechrecognition. • 1980s–Multichanneldeviceswithmultipleelectrodesites,whereallelectrodesarestimulatedatonce,orsequentially(whereelectrodesarestimulatedoneatatime).Withthesedevicestheunderstandingofspeechwithoutlipreadingwasachieved. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 10 www.itk.ppke.hu MAIN PARTS OF COCHLEAR IMPLANTS 1. Microphone 2. Externally worn speech processor (body worn or behind the ear (BTE)) 3. Inductive link (coil) 4. Implanted receiver-stimulator 5. Electrode array Figure2.showsaschematicrepresentationofthecomponentsofacochlearimplant,whileonFigure3.youcanseethepartsofthedeviceinrelationshipwiththehumanearstructures. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 11 www.itk.ppke.hu CI_schematics.jpg Figure 2. Schematic representation of a cochlear implant. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 12 www.itk.ppke.hu SIMPLIFIED WORKING MECHANISM OF THE COCHLEAR IMPLANTS 1. Sounds are picked up by the microphone in the audio (speech) processor. 2. The audio processor analyses and codes sounds into a special pattern of digital information. 3. This information is sent to the coil and is transmitted across the skin to the implant. 4. The implant (receiver-stimulator) interprets the code and sends electrical pulses to the electrodes in the cochlea. 5. The auditory nerve picks up the signals and sends them to the auditory centrein the brain. The brain recognizes these signals as sound. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 13 www.itk.ppke.hu Cochlear_Implant_1.jpg Figure 3. The sturctureof the human ear and the main parts of the cochlear implant (commons.wikimedia.org) wikimedia_logo.bmp NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 14 www.itk.ppke.hu EXTERNAL UNIT (SPEECH PROCESSOR) Theexternalunittakesitsinputfromamicrophone.Ithas3maincomponents: • Digitalsignalprocessing(DSP)unit • Poweramplifier • Radiofrequency(RF)transmitter NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 15 www.itk.ppke.hu EXTERNAL UNIT (SPEECH PROCESSOR) Thedigitalsignalprocessor(DSP)unitextractsfeaturesfromthesoundpickedupbythemicrophoneandconvertstheseintoastreamofbits,whicharethantransmittedbytheRFlinktotheimplantedinternalunit.TheDSPcontainsamemory,whichstorespatient-specificinformation.Itperformsalsoafrequencymapping(allocatingfilterchannelstoelectrodes)andanamplitudemapping(optimizingtheloudnesstoimprovespeechperception).DependingonthedesigntheDSPmayalsoprocessbacktelemetryinformationfromtheinternalunit. Theprocesseddataistransmittedthroughantranscutaneouselectromagneticlink.TheRFtransmitterisapairofinductivelycoupledcoils.Ittransmitsbothpoweranddataandusesaframeorpacketcodingschemefortransmission.Radiofrequenciesbetween2.5and50MHzareused.Thetransmitteddataisamplitudeandfrequencymodulated.Theefficiencyofthelinkisamajordeterminingfactorofbatterylifeandbatterysize.(70%ofavailablepowerisconsumedbythetransmissionlink) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 16 www.itk.ppke.hu ProductName RF StimRate No. of CurrentSources Nucleus24 (Cochlear) 5 MHz 14400 Hz 1 Sonata(Med-El) 12 MHz 50700 Hz 12 (12electrodes) ClarionHiRes90K (Advanced Bionics) 50 MHz 83000 Hz 16 (16electrodes) PARAMETERS OF A FEW TYPES OF COCHLEARIMPLANTS: NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 17 www.itk.ppke.hu IMPLANTED INTERNAL UNIT Thereceiver-stimulatorconsistsofareceivercoil(RFreceiver),adecoder,andachargedeliverysystem(stimulator).Thereceivercoil,whichisinmagneticcouplingwiththetransmittercoilandislocatedundertheskin,picksupboththepowerandthedatatransmittedfromtheexternalcoil.Thedataisdecodedtoproducethecurrentwaveformusedtostimulatetheauditorynerveviatheelectrodeslocatedinthescalatympani. Inmoderndevicesthereisalsofeedbackloopthatmonitorscriticalelectricandneuralactivitiesintheimplantandtransmitstheseinformationbacktotheexternalunit(backtelemetry).Backtelemetryallowstheexternalunittocheckstatusoftheinternalunitandtomeasureandmonitorcriticalinformationregardingtheelectrode-tissueinterface(electrodeimpedance,electrodefieldpotential,neuralresponses). Theimplantelectronicsisdesignedtolastthepatient’slifetime.Theinternalunitispackagedinceramicorbiocompatiblemetal(titanium),hermeticallysealedtoavoidingressofmoisture. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 18 www.itk.ppke.hu block_diagram.jpg Figure4. Block diagram of the internal unitof a cochlearimplant NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 19 www.itk.ppke.hu THE ELECTRODE ARRAY Theelectrodearrayconsistsofanumberofplatinumcontactsdistributedalongaflexiblesiliconecarrierandisinsertedintothescalatympani.Thedesigngoalsoftheelectrodearrayaredeeperinsertiontobettermatchthetonotopicplaceofstimulationtothefrequencybandassignedtoeachelectrodechannel,improvingefficiencyofstimulation,andreducinginsertionrelatedtrauma. CochleardevelopedtheAdvancedOffStylet(AOS)techniqueforaneasierinsertionoftheelectrodearrays.Someparametersoftheelectrodearrayscanbereadhere: Length No. of contacts Contactspacing Shape 20-31.5 mm 6-22 0.75-2.4 mm Spiral, StraightorPre-curved NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 20 www.itk.ppke.hu SAFETY ISSUES Sterilization to eliminate infection Mechanical design with its potential to cause structural tissue damage Energy exposure limits and the resulting tissue and neural damage Using biocompatible and non-toxic materials: titanium, platinum, iridium, gold, zirconium, ceramic, glass, silicone rubber, parylene, teflon Simulation safety is a top priority in the design of the stimulator: Parity check to detect bit errors from transmission or data decoding Stimulation parameter check Maximum charge check to prevent over stimulation Charge balance check to prevent unbalanced stimulation (shorting all stimulating electrodes between pulses) and DC stimulation (capacitors serially connected to the electrodes) Implant electronics is protected from electrostatic discharge NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 21 www.itk.ppke.hu SYSTEM ISSUES • Powerconsumptionisbetween13and250mW(speechprocessor10%,RFlink70%,implantedinternalunit20%) • Powersources:disposablezincair„button”cellsdevelopforthehearingaidindustry(lastingfor16-120hours)orNickelMetalHybridrechargeablecellsorpolymer-lithiumioncells.(shortservicelife,rechargingofbatteriesonadailybasis) • Anormalhearinghasa120dBdynamicrange,200discriminablestepsandloudnessgrowsasapoweroffunctionofintensity.Acochlearimplantuserhasa10-20dBdynamicrange,20discriminablestepsandloudnessgrowsasanexponentialfunctionofelectriccurrents. • The faster the stimulation rate, the more accurate the timing ofsound. • The higher the spectral resolution, the more detailed sound youhear. • The wider the input dynamic range, the moresoundsyouhear NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 22 www.itk.ppke.hu ELECTRICAL STIMULATION STRATEGIES Stimulation possibilities: • Analog • Pulsatile (sequential or simultaneous stimulation) with biphasispulses: 20-200 us (Figure 5., Figure 6.) Electrode configurations (Figure 7.): • Monopolar • Bipolar NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 23 www.itk.ppke.hu Figure5.Sequential(interleavedpulses)stimulationandsimultaneousstimulationusedonfourdifferentchannels.Incaseofsequentialstimulationoneelectrodeisstimulatedatonetime.(T-pulseduration,1/ratedurationbetweenpulses) sim_nonsim.jpg NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 24 www.itk.ppke.hu bi_tri_pulses.jpg Figure6.Varioussignalshapescanbeusedforelectricalstimulationwithdifferenceintheamplitudeordurationtime.Biphasicpulsesarethecommonsignalshapesusedforstimulationofcochlearimplantelectrodes. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 25 www.itk.ppke.hu ELECTRICAL STIMULATION STRATEGIES Coding temporal information into electrical waveforms: 1. Analogwaveforms-Theacousticsignalisfiltered,compressedandtransmittedasananalogsignal. 2. Pulsetrains–Thefrequencyofthepulsescorrespondstosomefrequencyintheacousticsignal. 3. Amplitude-modulatedpulsetrains–Therateofthepulsetrainisfixedandcomponentsoftheacousticsignalareselectedtomodulatetheamplitudeofthepulsetrain. Analogwaveformcarriesthemostinformation.Sometemporaldetailislostinthetwopulsatilestrategies,buttheyhavetheadvantagethatdifferentchannelscanbestimulatedatdifferenttimes.(noproblemswithcurrentinteractiononadjacentchannels) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 26 www.itk.ppke.hu MONOPOLARAND BIPOLAR STIMULATION STRATEGIES • Inamonopolarmode,thereturnelectrodeislocatedoutsideofthecochlea,usuallyinthetemporalismusclebehindtheearbutcanbeattachedtothecasehousingtheinternalelectronics.(activeelectrodesarelocatedfarfromthereference(ground)electrode,Figure7.leftside) • Inabipolarmode,thereturnelectrodeisanadjacentintro-cochlearelectrodetothestimulationelectrode.(activeandreferenceelectrodesareplacedclosetoeachother,Figure7.rightside) • Inatripolarmode,thereturnelectrodesaretwoadjacentelectrodeswitheachreceivinghalfofthecurrentdeliveredtothestimulatingelectrode. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 27 www.itk.ppke.hu bipolar_monopolar.jpg Figure 7. Two different electrical stimulation strategies: monopolarand bipolar electrode configuration NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 28 www.itk.ppke.hu ELECTRICAL STIMULATION STRATEGIES Features of electrical stimulation important for electrical hearing: • Temporal features: • Analog stimuli: Frequency and phase • Pulsatile stimuli: Phase duration, Pulse rate, Pulse polarity • Analog or pulsatile stimuli: Stimulus duration, Duty cycle • Spatial features:• Electrode location • Electrode orientation • Electrode site separation • Electrode configuration: Multipolar, Tripolar, Bipolar, Monopolar • Stimulus level:• Operating range, Compression algorithm NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 29 www.itk.ppke.hu ELECTRICAL STIMULATION STRATEGIES Electricalstimulationstrategiesorspeechprocessingstrategiesdeterminethewayinwhichvariousfeaturesoftheacousticsignalareselectedandhowthosefeaturesarerepresentedacrossthevariouschannelsofprosthesis.ThemainstrategiescanarelistedonthenextslideandarealsoshownonFigure8.Someofthesewillbedetailedinthenextfewslides.TherecentlydevelopedhighratestimulationstrategiesliketheHiResolutionfromAdvancedBionicsorTempofromMed-Elarenotpresentedhere. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 30 www.itk.ppke.hu SPEECH PROCESSING STRATEGIES Strategy Name Abbreviation Compressed Analog CA Simultaneous Analog Stimulation SAS Continuous Interleaved Sampling CIS F0/F1/F2 F0/F1/F2 Multipeak MPEAK Spectral Maxima Sound Processor SMSP Spectral Peak SPEAK Advanced Combination Encoders ACE Paired Pulsatile Sampler PPS Multiple Pulsatile Stimulation MPS NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 31 www.itk.ppke.hu Speec_proc_strat.jpg Figure8.Differentspeechprocessingstrategiesusedincochlearimplants.Somestrategiesdevelopedrecentlyarenotindicated(liketheTempofromMed-ElortheHiResolutionfromAdvancedBionics). NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 32 www.itk.ppke.hu CONTINUOUS INTERLEAVED SAMPLING (CIS) CISstrategyisimplementedbyallmajormanufacturers.Thesoundrecordedbyamicrophoneentersband-passfilters(5-20,numberofBPFsidenticaltothenumberofelectrodes)withdifferentcutofffrequencies.Thetemporalenvelopefromeachbandisextractedbyrectificationfollowedbyalow-passfilter.Thecutofffrequencyofthelow-passenvelopefilterisaround160-320Hz.Afterthat,theenvelopeislogarithmicallycompressedtomatchthewidelyvaryingacousticamplitudestothenarrowelectricdynamicrange.Thiscompressedenvelopeamplitudemodulatesafixed-ratebiphasiccarrier.(100-1000Hz/s).Carriersaretimeinterleavedbetweenthebandstoavoidsimultaneouselectricalfieldinterference(nosimultaneousstimulationoccursbetweenthebandsatanytime).Thisnon-simultaneousstimulation(Figure9.)needsonlyonecurrentsourcewithamultiplexer.Theslowlyvaryingtemporalenvelopesfrom3to4spectralbandscandeliverhighlevelsofspeechintelligibilityinquiet.TheschematicrepresentationcanbefoundonFigure10. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 33 www.itk.ppke.hu CIS1.jpg Figure9.InterleavedpulsesusedonfourelectrodesincaseoftheContinuousInterleavedSamplingstrategy(CIS).Tisthepulsedurationand1/rateisthedurationbetweenpulsesoneachchannel. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 34 www.itk.ppke.hu CIS2.jpg Figure10.ContinuousInterleavedSampling(CIS)strategy. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 35 www.itk.ppke.hu COMPRESSED ANALOG (CA) AND SAS TheCAstrategydeliversband-specific,amplitude-compressedanalogwaveformstodifferentelectrodelocationsinthecochlea.Thesoundpickedupbyamicrophoneisattenuatedoramplifiedbytheautomaticgaincontrol(AGC)dependingonenvironmentalcircumstances(e.g.thedistanceofthetalkerfromthemicrophone).Thesignalisthendividedintofrequencybandsbypassinganumberofband-passfilters.(OnFigure11.thereare4BPFs)Afterthatthenarrow-bandsignaliscompressedinamplitudetomatchthewidelyvaryingacousticamplitudestothenarrowelectricdynamicrange.Thecompressedanalogsignalsareconvertedtocurrentsanddeliveredtodifferentelectrodesinthecochlearelectrodearray.Allelectrodesarestimulatedsimultaneously.SimultaneousAnalogStimulation(SAS)usesabipolarstimulationconfiguration,thiswaythereislesscurrentspreadcomparedtoamonopolarconfiguration. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 36 www.itk.ppke.hu CA.jpg Figure11.CompressedAnalog(CA)andSASstrategy. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 37 www.itk.ppke.hu F0/F1/F2 IntheF0/F1/F2strategy(Figure12.)spectralpeaksorformants,whichreflecttheresonancepropertiesofthevocaltract,areextractedanddeliveredtodifferentelectrodesaccordingtothepresumedtonotopicrelationshipbetweentheplaceoftheelectrodeanditsevokedpitch. TheF0fundamentalfrequency(below270Hz),thefirstformant(F1,300-1000Hz)andthesecondformant(F2,1000-3000Hz)areextractedfromthesoundsignalwiththehelpofzerocrossingdetectors.Twoelectrodesareselectedforpulsatilestimulation,onecorrespondingtothefrequencyofthefirstformant(5mostapicalelectrodes)andonecorrespondingtoF2frequency(remaining15electrodes).ThepulserateiscontrolledbytheF0forvoicedsegments(F0pulses/sec)andforunvoicedsegmentstheelectrodesarestimulatedataquasi-randomrate(withanaveragerateof100pulses/sec).TheF0/F1/F2strategyuses200µslongbiphasicpulseswith800µsspacingbetweenthepulsestoavoidinteractionbetweendifferentchannels. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 38 www.itk.ppke.hu F0F1F2.jpg Figure12.F0/F1/F2strategyintheNucleusWearableSpeechProcessor(WSP) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 39 www.itk.ppke.hu MULTIPEAK (MPEAK) TheMPEAKstrategyisanimprovedversionoftheF0/F1/F2strategy.SimilartotheF0/F1/F2strategy,F1andF2formantfrequencieswereextractedusingzero-crossingdetectorsandtheiramplitudeswerecalculatedusingenvelopedetectors.Thefrequencyrangeofthesecondformantwaschangedto800-4000Hz.Additionalhighfrequencydataiscomputedinthreedifferentfrequencybands(2000-2800Hz,2800-4000Hz,4000-6000Hz)toenhancetherepresentationofF2andincludehigh-frequencyinformation(importantforperceptionofconsonants).Electrodes1,4and7areallocatedtotheoutputoftheseband-passfilters.FourelectrodesarestimulatedatarateofF0incaseofvoicedsegments(F1,F2,electrodes4and7)andatquasi-randomintervalsforunvoicedsounds(F2,electrodes1,4,7).OnFigure13.youcanseeaschematicimplementationoftheMPEAKstrategy. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 40 www.itk.ppke.hu mpeak.jpg Figure13.MPEAKstrategyintheCochlearMiniatureSpeechProcessor(MSP) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 41 www.itk.ppke.hu SPECTRAL MAXIMA SOUND PROCESSOR (SMSP) TheSMSPstrategyanalysisthespeechwaveforminsteadofextractingfeaturesfromthesignal.Ituses16band-passfiltersandaspectralmaximadetector.Thepre-emphasizedsignal(preamplifiedsoundsignalpickedupbythemicrophone)isprocessedthroughthebankof16band-passfilters(frequencyrangefrom250to5400Hz).Afterenvelopedetection(rectificationand200Hzlow-passfiltering)thesixlargestenvelopeoutputsareselectedforstimulationin4msintervals.TheselectedamplitudesarelogarithmicallycompressedandtransmittedtothesixselectedelectrodesthroughtheRFlink.Thelargestenvelopesarenotnecessarilythespectralpeaks,several„maxima”maycomefromasinglespectralpeak.Sixinterleaved(non-simultaneous)biphasicpulsesaredeliveredtotheselectedelectrodesatarateof250pulses/s.OnFigure14.youcanseeaschematicimplementationoftheSMSPstrategy. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 42 www.itk.ppke.hu SMSP.jpg Figure14.SMSPstrategyintheNucleusSpectralMaximaSoundProcessor NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 43 www.itk.ppke.hu „N-OF-M” STRATEGY The„n-of-m”strategyisthebasisoftheSPEAKandACEstrategies.ItissimilartoCIS,thereareband-passfiltersandtheenvelopeextractionblock,butthereisgreaternumberofband-passfilters.(e.g.,m=22,usuallythenumberofelectrodesites).Itisbasedontemporalframeslasting2.5-4ms.Afterband-passfilteringandenvelopeextraction„n”numberofbandswiththelargestenvelopeamplitudeareselected.Afterthat,theprocessisthesameasbytheCISstrategyandonlythechosen„n”electrodesarestimulated.TheSPEAKstrategyselects6-10largestpeaksandhasafixed250Hzperchannelrate.TheACEstrategyhasalargerrangeofpeakselectionandhigherratethantheSPEAKstrategy.If„n”equals„m”thentheSPEAKandACEstrategiesareessentiallysameastheCISstrategy.OnFigure15.youcanseeaschematicimplementationofthe„n-of-m”strategy. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 44 www.itk.ppke.hu nofm.jpg Figure15.The„n-of-m”strategy NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 45 www.itk.ppke.hu AUDITORY PERFORMANCE OF CI USERS Auditoryperformance(AP):theabilitytodiscriminate,detect,identifyorrecognizespeech.Wecanmeasureitwiththepercentcorrectscoreonopen-setspeech-recognitiontests. Theauditoryperformanceisaffectedbyseveralfactorsforexamplethenumberofelectrodesusedforstimulation(Figure17.),electrodeplacementandinsertiondepth(Figure18.). Thethree-stagemodelofauditoryperformanceshowsthechangesoftheAPindifferenttimeperiodsofpostlinguallydeafenedpeople(detailsonFigure16.). NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 46 www.itk.ppke.hu FACTORS AFFECTING THE PERFORMANCE OF CI USERS Durationofdeafness:hasastrongnegativeeffectonauditoryperformance.Shorterdurationofauditorydeprivationprovidesbetterauditoryperformance. Ageofonsetofdeafness:hasamajorimpactonthesuccessofCIs.Peoplewithpostlingualdeafnessperformbetterthanpeoplewithprelingualorcongenitaldeafness. Ageofimplantation:Peopleimplantedatanearlyageseemtoperformbetterthanpeopleimplantedinadulthood. Durationofcochlearimplantuse:DurationofexperiencewiththeCIhasbeenfoundtohaveastrongpositiveeffectonauditoryperformance. Otherfactors:numberofsurvivingspiralganglioncells,numberofelectrodesused(Figure17.),electrodeplacementandinsertiondepth(Figure18.),electricaldynamicrange,signalprocessingstrategy,socialsupport NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 47 www.itk.ppke.hu three_stage_model.png Figure16.Thethree-stagemodelofauditoryperformance(AP)forpostlinguallydeafenedadults.Stage1beginsafternormallanguagedevelopment.(AParound100%)Stage2beginsattheonsetofdeafness.(immediatedropintheAPandafurtherdecreaseuntilimplantation)Stage3beginswiththeimplantation(increaseintheAP,andrisesfurtherasaresultoflearningandexperience) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 48 www.itk.ppke.hu SPEECH PERFORMANCE Withonechanneltherecognitionofsentencesispoor,butwithfourchannels,performanceisnear100%forsimplesentencesinaquietbackground.(Figure17.)Innoisybackgroundsmorechannelsarerequiredforahighauditoryperformance.Speechrecognitionscoresincreasesasafunctionofthechannelnumberupto4-8channelsandthenasymptotes(nofurtherincreaseformorethan8channels,Figure17.) Theageisextremelycrucialforthechild’slanguageandcognitivedevelopment,thereforeimplantationsinchildhoodhaveverygoodresults.Ithelpsthechildrentobeabletospeakclearlyandtoabletounderstandspeech.SomechildrenmightgetmorebenefitformaCIthanfromatraditionalhearingaid.BothprelinguallyandpostlinguallydeafenedchildrenbenefitfromCI.Prelinguallydeafenedchildrenacquirethespeechproductionandspeechperceptionskillsataslowerrate. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 49 www.itk.ppke.hu no_of_electrodes.png Figure17.Theunderstandingofspeechdependingonthenumberofelectrodes.Meanpercentcorrectscoresonrecognitionofconsonants,vowelsandsentencesasafunctionofnumberofchannels.Verygoodauditoryperformancecanbeobtainedwith5-8independentchannelsofstimulation. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 50 www.itk.ppke.hu insertion_depth.png Figure18. The effect of the insertion depth of theimplantonvowelrecognition. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 51 www.itk.ppke.hu THE BIGGEST COMPANIES RELATED TO COCHLEAR IMPLANTS AND THEIR PRODUCTS Company Name Company Headquarters Offered Cochlear Implant (2010) Cochlear Australia Nucleus 5 System Med-El Austria MAESTRO Cochlear Implant System Advanced Bionics USA Harmony HiResolution Bionic Ear System Neurelec France Digisonic SP Cochlear Implant System NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 52 www.itk.ppke.hu MED-EL MAESTRO COCHLEAR IMPLANT SYSTEM Med-ElMAESTRO(Figure19.)ismedicaloptionforindividualswithseveretoprofoundsensorineuralhearingloss.Thesystemcontainsfeaturesoptimizedfortheappreciationofmusicandforlisteninginchallengingsituations.TheMAESTROCIconsistsofaninternal(CONCERTO,SONATAti100orPULSARci100)andanexternalcomponent(OPUS1orOPUS2withtheFineTunerremotecontrol).Theinternalimplantissurgicallyplacedundertheskinjustbehindtheear.Itconsistsofadurablehousing,whichcontainselectronics,theareceivingantennaandamagnet,andtheelectrodearray,whichisimplantedintothecochlea.CONCERTOandSONATAhasatitaniumhousing,whilePULSARismadeofimpactresistantceramicandistheworld’ssmallestCI.Theexternalcomponentisanaudioprocessor,whichiswornontheear.Itconsistsofacontrolunit,abatterypack,andacoilthattransmitsinformationthroughtheskintothereceiverintheimplant. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS Opus2_Processor.jpg 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 53 www.itk.ppke.hu Figure19.Parts of the Med-El Maestro Cochlear Implant Sytem http://www.medel.com/ OPUS1_Processor.jpg PULSARci100.jpg MAESTRO_cross_section_graphics.jpg CONCERTO.jpg SONATAti100.jpg SONATAti100 CONCERTO OPUS 1 OPUS 2 PULSARci100 medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 54 www.itk.ppke.hu MED-EL MAESTRO: FEATURES AND BENEFITS • AutomaticSoundManagementdetectschanginglisteningsituationson-the-go,adaptingautomatically,sotheuserdonothasto. • FineHearingtechnologyintroducesanewdimensiontomusicalperception.Itprocessesalsothefinedetailsofsound,andprovidesadditionalpitchinformation,especiallyinthelowfrequencies,thatisessentialfortheappreciationofmusic. • CompleteCochlearCoverage:theelectrodearrayisinsertedthroughtheentirelengthofthecochlea.Thishastheadvantagetostimulatealsointheapexofthecochlea,wherethelowfrequenciesarerepresented. • The FineTunerremote control allows users to make changes to volume or sensitivity while keeping the processor on the ear. (Only for OPUS 2) • Built-in telecoil, wireless access to FM, Bluetoothand Assistive Listening Devices. • Battery life of up to a week. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 55 www.itk.ppke.hu COCHLEAR NUCLEUS 5 SYSTEM TheNucleus5system(Figure20.)consistsoftheCochlearNucleusCP810SoundProcessorwithtitaniumfoundation(itistheindustry’ssmallestsoundprocessorandtheworld’smostwater-resistantsoundprocessor,andsupportsACE,CISandSPEAKsoundcodingstrategies),theCochlearNucleusCI512CochlearImplant(industry’sthinnesttitaniumcochlearimplant),andtheCochlearNucleusCR110RemoteAssistant(toadjustthesoundprocessorwirelessly).Theelectrodearrayhasacurveddesign,with22electrodesandwithaccessto161intermediatepitches.Thestimulationrateisupto30000pulsespersecondandonechannelisstimulatedatonetime.TheNucleus5systemprovidestheindustryleadinghearingperformancewiththehighestspeechrecognitionscoresinamulti-centerclinicalstudy.ItisMRIcompatibleandcompatiblewithFMsystems,canconnecttoanymusicandgamingsoundsourcewithaheadphonejack.Ithasabatterylifearoundtwodays. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 56 www.itk.ppke.hu speech_proc_med_1_1.jpg Figure20. The Cochlear Nucleus 5 System http://www.cochlear.com/ cochlear_hearalways_logo.gif Cochlear Nucleus CP810 Sound Processor Cochlear Nucleus CI512 Cochlear Implant Cochlear Nucleus CR110 Remote Assistant NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 57 www.itk.ppke.hu COCHLEAR NUCLEUS 5 SYSTEM: FEATURES • AutoPhoneforautomaticphonedetectionthroughautotelecoil.Thetelecoilautomaticallyactivateswhenaphoneisheldnexttothesoundprocessor. • TheSmartSoundtechnology’sSetItandGoprogramautomaticallyadaptstotheenvironmentaroundtheuser,itintelligentlyadjuststofittheuniqueenvironmentsautomatically.SetItandGorefinesandclarifiessoundindifferentenvironmentsforaricher,clearerlisteningexperience.SmartSoundtechnologyhasalsopowerprogramslikeMUSIC,FOCUSandNOISE. • Dualmicrophonezoomtechnologywasdesignedtoenhancehearingperformanceinnoisyenvironmentsandisaveryeffectivewaytoimprovespeechperformanceinnoise. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 58 www.itk.ppke.hu ADVANCED BIONICS HARMONY HIRESOLUTION BIONIC EAR SYSTEM ThecochlearimplantofAdvancedBionicsconsistsoftheHarmonyBTE(BehindtheEar)SoundProcessorandtheHiRes90KImplantwithHiFocuselectrodesforneuraltargeting.TheHiRes90KImplantcanmanage90Kdataupdatespersecond,upto83000stimulationpulsespersecondandup120bandsofspectralinformation.Ithasaninternalmemory,abidirectionaltelemetry,andaremovablemagnetforMRIscans.Itsupports(togetherwiththesoundprocessor)severalsoundcodingstrategies:HiRes-SwithFidelity120,HiRes-PwithFidelity120,HiRes-S,HiRes-P,CISandMPSprogrammingmodes.TheHarmonysoundprocessorhasanelectronicallyintegratedtelecoilandabatterylifearoundoneday.Anothertwosolutionsofsoundprocessorsareavailable:thePlatinumSeriesSoundProcessor(PSP)isadiscreetbody-wornprocessorwiththesameprocessingprogramsastheear-levelprocessorsandtheAuriaBTESoundProcessorisalightweightsolutionforhigh-resolutionsound. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 59 www.itk.ppke.hu AB HARMONY SYSTEM -FEATURES •HiResolutionSound:Ithasfivetimesmoreresolutionthananyothercochlearimplantsystem. •HiResFidelity120:Offers120spectralbandsforunsurpassedspectral(pitch)resolutiontohearallthecolorfuldetailsofsound. •AutoSoundProcessing:Automaticallyadaptstotheuserssurroundingsorcontinuallymakesadjustmentstokeepupwithchangingsoundenvironments. •ClearVoiceisastrategy,builtonHiResFidelity120technology,andisdesignedtoautomaticallyanalyzeandadapttoeachlisteningsituationencounteredthroughouttheday,separatingthedistractingnoisesfromspeech. •T-Mic™Microphone:theonlymicrophoneplacednaturallyattheopeningoftheearforhighlyfocusedhearingwhileprovidingwirelessconnectivitytocellphones,MP3players,andmore. •WideIDR(inputdynamicrange)enablestohearmoresoundwithlessdistortionsothatitiseasiertohearmusicandmakeoutlyricsandindividualinstruments. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 60 www.itk.ppke.hu NEURELEC DIGISONIC SP SYSTEM ThemainpartsoftheDigisonicSPsystemistheSAPHYR(SAPHYRSPandSAPHYRCX)withtwoomnidirectionalmicrophones,anauxiliaryUltra-LowNoisesocket(connectionpointtodifferentaudiosourcesandFMsystems),ahigh-precisionelectroniccardandanintegratedtelecoil.TheDoubleDSPtechnologyassurescompatibilitywiththeoldergenerationsofimplants,whileofferingfourtimesmoresoundprocessing.Thesoundprocessoroffers4programsandalongbatterylifeofseveraldays.AnothersoundprocessorsfromNeurolecaretheDigisonicBWandDigisonicBTE.TheinternalpartofthesystemistheDigisonicSPimplant(fixedwithscrewstotheskullduringthesurgery),whichconsistsofasmallceramicandtitaniumboxandanelectrodearraywith20electrodes(inserted25mmdeepintothecochlea).Itsupportsmonopolarorcommongroundstimulationthroughbiphasicpulses.Thestimulationfrequencyis24000pulsespersecond.TheimplantiscompatiblewithMRItestsat1.5Tesla.TwoothertypeofimplantsaretheDigisonicDX10andtheDigisonicCONVEX. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 61 www.itk.ppke.hu ELECTRIC ACOUSTIC STIMULATION (EAS) Thereisacertainpatientgroupthathassomedegreeofresidualhearinginthelowfrequenciesandaseverehearinglossinthehighfrequencies(partialdeafness).Theysufferfrominadequatespeechcomprehension,eveninthebestaidedcondition.Ontheiraudiogramthereisnoorjustamoderatehearinglossvisiblebelow1.5kHz,butabove1.5kHzthereisaseveretoprofoundsensorineuralhearingimpairmentpresent.ForthetreatmentofthistypeofhearinglossElectricAcousticStimulationisagoodsolution.EASistheuseofatraditionalhearingaidandacochlearimplanttogetherinthesameear.Thehearingaidacousticallyamplifieslowfrequencies(<1kHz),whilethecochlearimplantelectricallystimulatesthemiddleandhighfrequencies(1-8kHz).Theinnerearprocessesacousticandelectricstimulisimultaneously.Theinsertiondepthofthecochlearimplantelectrodeisbetween18-22mm,topreservethelow-frequencyhearing.Med-EloffersanEASHearingImplantSystem,withaninternalcomponent(SONATAorPULSAR,andFLEXElectrodeArray)andanexternalaudioprocessor(DUET).(Figure21.) NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS SONATA.jpg DUET.jpg 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 62 www.itk.ppke.hu Electric-Acoustic-Stimulation-EAS.png Figure21.Parts of the Med-El EAS Hearing Implant System PULSAR.jpg FLEX2.JPG DUET audio processor SONATAti100 PULSARci100 FLEX Electrod Array http://www.medel.com/ medel_logo.jpg NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 63 www.itk.ppke.hu AUDITORY BRAINSTEM IMPLANT (ABI) Auditorybrainstemimplantsarerequiredwhentumors(usuallycausedbyneurofibromatosistype2orNF2)involvingalsotheacousticnerve,havetobesurgicallyremoved.Thedamageofthecochlearnervesresultsindeafness,andinthiscaseotherimplantablehearingaids,likecochlearimplantsorMEIHDscannotbeused.ABIbypassesthecochleaandcochlearnerve,andareimplantedintothelateralrecessofthefourthventricleadjacenttothecochlearnucleus.Itprovidesthepatientwithauditoryperceptionbyelectricallystimulating(bipolarormonopolar)theventralcochlearnucleus(thecochlearnucleuscomplexhastwoparts:theventralandthedorsalcochlearnucleus)withsurfaceorpenetratingelectrodes.Thegroundelectrodeisplacedinthetemporalismuscle.Thesurgeryandtheimplantationofthesystemisadifficulttask,becausethecochlearnucleusishardtoapproachandthesurfaceelectrodearrayisnoteasytofix,buttherecentlydevelopedmultichannelpenetratingelectrodesmaketheinsertionsafer(andalsoincreasetheprecisionofelectricstimulation,buttheyarestillinclinicalphase). NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 64 www.itk.ppke.hu AUDITORY BRAINSTEM IMPLANT (ABI) Aftertheinsertion,theelectrodeswithnonauditoryresponseshastobecollected(thisaredisregardedfurtheron).Theremainingelectrodes(withauditoryresponses)arepitchscaledandfinallytheimplantisprogrammed.ABIprovidesenoughauditoryinformationtofacilitatelip-readingabilitiesandafewareabletoachieveopen-set(nolip-readingcues)speechunderstanding. Thecompaniesmentionedinthecochlearimplantsectionhavealsodevelopedbrainstemimplants.TheNucleus24ABIissolutionproducedbyCochlearCorporation:theirdeviceincorporatesanarrayof21platinumdiscelectrodes(surfaceelectrodes),amicrophoneheadset,atransmittercoil,andadigitalspeechprocessor(SPrint)thatoffers4user-selectableprograms,aswellasprogrammablevolumeandsensitivitycontrols.TheprocessorusestheSPEAKspeechcodingstrategy.Med-Elhasa12electrodearrayimplantwithaspeechprocessorbasedontheC40+cochlearimplant,whileAdvancedBionicsdevelopeda16electrodearrayimplantbasedontheClarion-1.2CI.ThesolutionofNeurolecforpeoplewithNF2istheDigisonicSPABI. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 65 www.itk.ppke.hu AUDITORY MIDBRAIN IMPLANT (AMI) Itisthenewestmethodtorestorehearinganditisstillinexperimentalstage(clinicaltrialsin2007).TheinitialcandidatesarepeoplewithNF2(likeincaseofABI).TheAMIisimplantedatthesamesurgicalsettingwhentheacousticneuromasofNF2patientsareremoved.Theimplantationisperformedwiththehelpofa3DintraoperativesystemwithCTandMRIimagesbasedonbone-anchoredregistrationmethod.Electrodesareplacedintheinferiorcolliculus(IC),whichliesdownstreamfromthecochlearnucleusalongthecentralauditorypathwayandshareswiththisstructureatonotopicorganization.Thetargetisthecentralnucleusoftheinferiorcolliculus(ICC)butotherregionslikethelaterallemniscusandthedorsalcortexoftheICwerealsoimplanted.TheAMIhastheadvantageofbypassingthecochlearnucleusatthepons,whichmaybedamagedbytumorgrowth.Adisadvantageisapotentiallymorecomplicatedsurgicalapproach.TheICconsistsofawell-definedlaminatedorganizationandbecausetheselaminaecorrespondtodifferentfrequencylayersitalsohasawell-definedtonotopicorganization. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 66 www.itk.ppke.hu AUDITORY MIDBRAIN IMPLANT (AMI) -PARTS ApenetratingelectrodearrayhasbeendevelopedincollaborationwithCochlearCorporation,whichconsistsofasinglepinwith20platinumringelectrodeslinearlyspacedatintervalsof200micrometers.Thecontactsiteshaveawidthof100µm.Thesingle-shankmulti-sitearrayisdesignedaccordingthedimensionsofthehumanICwiththegoalofstimulatingthedifferentlayersoftheICC.Theringelectrodehasadiameterof0.4mmandis0.1mmwide.ItispositionedalongthetonotopicgradientoftheICC.Theelectrodesitesconnectedtoaparylene-coated25umthickplatinum-iridiumwire.TheDacronmeshanchorstheelectrodearrayontothesurfaceoftheneuraltissueandalsopreventsoverinsertationintotheIC.TheothercomponentsoftheAMIaresimilartoacochlearimplant:anexternalunitwithaprocessorandabehind-the-ear(BTE)microphoneandanimplantedreceiver-stimulatorinternalunit.TheAMIuseslowerstimulationcurrentvaluescomparedtocochlearimplants. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 67 www.itk.ppke.hu AUDITORY MIDBRAIN IMPLANT (AMI) –RESULTS ThreepatientswereimplantedwithAMI.SPEAKandACEstrategieswereusedforstimulation,withapulserateof250pps,apulsewidthof100µsandmonopolarconfiguration.AllthreepatientshaveobtainedhearingbenefitsfromtheAMIonadailybasis.Therewereimprovementsinlip-readingcapabilitiesandenvironmentalawareness.Theycoulddetecttemporalchangesinthestimulusanddifferencesinpitchperceptsdependingonthestimulatedsite(inICClowerpitchperceptsmoresuperficiallyandhigherpitchperceptsindeeperregions).Onepatientobtained50%correctforvowels,20%forconsonantsand40%fornumberswithAMIalone. NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 68 www.itk.ppke.hu WEBPAGES OF COMPANIES RELATED TO IMPLANTABLE HEARING AIDS • www.cochlear.com • www.medel.com • www.advancedbionics.com • www.neurelec.com • www.oticonmedical.com • www.envoymedical.com • www.otologics.com • www.ototronix.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 images.jpg NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 69 www.itk.ppke.hu LINKS RELATED TO HEARING AIDS Cochlearimplantsand EAS: http://hear-it.org/page.dsp?page=352 http://emedicine.medscape.com/article/857164-overview http://en.wikipedia.org/wiki/Cochlear_implant http://en.wikipedia.org/wiki/Electric_Acoustic_Stimulation ABI: http://en.wikipedia.org/wiki/Auditory_brainstem_implant http://www.youtube.com/watch?v=x6tkE97QrY8 http://www.asha.org/Publications/leader/2011/110315/Auditory-Brainstem-Implants.htm AMI: http://www.ncbi.nlm.nih.gov/pubmed?term=auditory%20midbrain%20implant NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS neuropr2.jpg 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 70 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 to cochlear implants on www.amazon.com cochl_brainstem.jpg cochlearimplants.jpg neural_prost.jpg neuropr.jpg NEURAL INTERFACES AND PROSTHESES:COCHLEAR IMPLANTS 2011.09.14.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 71 www.itk.ppke.hu REVIEW QUESTIONS • In which way can a cochlear implant (CI) provide hearing sensations? • What is the working mechanism of CIs? • What are the main parts and coding strategies of cochlear implants? • Choose one of mentioned speech coding strategies and describe it! • What is the difference between sequential and simultaneous stimulation? • What is the difference between monopolarand bipolar stimulation? • What is three-stage model of auditory performance? • How is the speech performance affected by the electrode insertion depth or the number of electrode sites? • Choose one of mentioned up-to-date CIsand describe it! • To whom is the EASsystem recommended? And the ABI? And the AMI?