1. Cochlear Implants Ryan S. Clement, PhD Neural Engineering and Applications Laboratory BioE 200: September 18, 2002

2. Anatomy and Physiology of Hearing External Ear Ear Canal Adapted from: http://funsan.biomed.mcgill.ca/~funnell/AudiLab/501/mmem003.html Cochlea Middle Ear Bones Ear Drum

3. Anatomy and Physiology (con’t) http://www.iurc.montp.inserm.fr/cric/audition/ Traveling Wave Movie Cochlear Cross-section http://shark.me.nus.edu.sg/~asme/MechHear.htm ©Howard Hughes Medical Institute

4. Sound Transduction Basilar Membrane Auditory Nerve Cochlear cross-section (single turn) Cochlea Hair Cells http://www.iurc.montp.inserm.fr/cric/audition/

5. Sensorineural Hearing Loss Causes –Heredity –Genetic –Aging process –Ototoxic drugs –Excessive exposure to loud sounds Microscopic view of hair cells. OHCs IHCs

6. Electrical Stimulation Can Allow Us to Bypass Damaged Haircells

7. A Brief History Volta (1790) –metal rods and battery induced sounds like boiling liquid! Djourno and Eyries (1957) –First demonstration of direct electrical stimulation of auditory nerve House and Urban (1972) –Develop and test first prototype (single channel) –House/3M device gets FDA approval in 1984

8. A Brief History (con’t) Clark, University of Melborne (1978) –Implant first multi-channel device –FDA approval in 1985 From then till now: –continual improvements have been made in speech processing strategies and electrode design –Many patients can use the devices without the aid of lip-reading (even the telephone!)

9. Safety Considerations Biomaterials: with the proper choice of materials there is no infection, just a minor fibrous sheath around the implant. Electrode Insertion trauma: factors: surgical technique, dimensions, array’s mechanical properties If damage occurs to basilar membrane and dendrites, could lead to retrograde deterioration. However, are few and far between in most sensorineural hearing loss cases. For most part damage is minimal. Chronic Electrical Stimulation Platinum electrodes: virtually no corrosion or depletion Doesn’t destroy AN, in fact can help keep auditory nerve and cells in cochlear nucleus healthy (Leake et al 1992) impedances and thresholds stabilize several days post implant

10. (The University of Melbourne) Current Facts About Cochlear Implants Quick Facts: candidacy: severe-to-profound sensorineural deafness ~70,000 recipients worldwide (~21,000 in the U.S.) * 50% children (12 mo-17 years); 50% adults * Manufacturers:  Cochlear Corporation: Nucleus TM  Advanced Bionics: Clarion TM  Med-EL: Combi-40+ TM  AllHear: AllHear TM single channel  Antwerp Bionic Systems: Laura TM (now owned by Cochlear)  MXM Laboratories: Digisonic TM * FDA survey of venders 11/2001 http://www.nidcd.nih.gov/health/pubs_hb/coch.htm#c Cochlear Corporation: Nucleus TM FDA approved

11. Company founded by Dr. House Shorter insertion; claims to retain residual hearing in implanted ear Single stimulation channel Not yet approved for sale in United States http://www.allhear.com/

12. Cochlear Corporation Contour Speech Processors Company created out of Greame Clark’s work at the University of Melbourne, Australia First FDA approved multichannel devices 22 channels available for stimulation

13. Advanced Bionics The Clarion II Implant Based on work conducted at UCSF Only American Company 16 channels with 16 individual current drivers

14. Med-El Corporation Combi 40/40+ Implant Headquarters in Austria case for less signal loss and power consumption 12 channels of stimulation Processors

15. Transmission Link Block Diagram for Typical Cochlear Implant System Skin External ComponentsInternal Components

16. The Speech Signal “Never touch a snake with your bare hands.”

17. Progression of Speech Processing Strategies

18. Speech Processing Sound Input Electrical Stimulation

19. Cochlear Frequency Tuning The cochlea is arranged such that different regions of the cochlea correspond to different pitches. Multichannel cochlear implants take advantage of this fact to encode different frequencies in the speech signal.

20. Cochlear Electrodes Cochlear Electrode Cochlea Auditory Nerve Cochlear Corporation’s Nucleus Electrode

21. What might cochlear implants sound like? Cochlear implant simulations: –Single channel –2 channels –3 channels –4 channels –6 channels –8 channels (created from Bob Shannon and Philip Lizou’s model)

22. Dorman 2002

23. Factors Effecting Cochlear Implant Performance Duration of deafness Age of onset of deafness Age at implantation Duration of cochlear implant use Other: –Number of remaining auditory nerve fibers –Electrode placement and insertion depth –Dynamic range

24. Future Research Directions Better understanding of fundamental mechanisms Better speech processing algorithms Improved enjoyment of music Electrode design improvements Objective fitting for young children Aesthetics (smaller, totally implantable)

25. Cochlear Implant Research Team Requires integration of many disciplines: –Bioengineering –Physiology –Otolaryngology –Speech Science –Signal Processing