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Ruth Litovsky University of Wisconsin Madison, WI USA

Ruth Litovsky University of Wisconsin Madison, WI USA. Brain Plasticity and Development in Children and Adults with Cochlear Implants. Litovsky@waisman.wisc.edu http:/ /www.waisman.wisc.edu. Waisman DWE June 23 2013. How are CI users doing?.

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Ruth Litovsky University of Wisconsin Madison, WI USA

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  1. Ruth LitovskyUniversity of WisconsinMadison, WI USA Brain Plasticity and Development in Children and Adults with Cochlear Implants Litovsky@waisman.wisc.edu http://www.waisman.wisc.edu Waisman DWE June 23 2013

  2. How are CI users doing? The CI converts acoustic input into electrical stimulation of the auditory nerve to provide: • Speech/Language • Music • Sound localization • Quality of life • Etc…

  3. How are CI users doing? World-wide ~ 250,000 recipients • Speech/Language • Music • Sound localization • Quality of life • Etc…

  4. How are CI users doing? • Is the glass “half full” or “half empty” ? • The field has come a long way…. Many CI users have excellent speech production and receptive language skills. • But, other CI users struggle to attain speech and language, especially without “speech reading” (auditory only)

  5. Language comprehension Language expression Niparko et al. (2010)

  6. Our recent research shows that:1) Language perception: most children are within 1 SD of mean2) Language production: >50% children +/- 1SD; some are below Language expression Language comprehension

  7. Who are the children we study? • Bilateral cochlear implants • High maternal education • SES is generally high • Children have high IQ and memory testing scores • Not typical of CI population, but likely provide information on “best possible outcomes”

  8. Bilateral Cochlear Implants • Bilateral CIs provided to growing number of patients. • Goal: Improve hearing in noise, sound localization, quality of life. • Age of bilateral activation in many clinics is 12 months or younger. • But are we providing them with the best possible input that will maximize outcomes?

  9. Studies in adults: Sound localization in Noise 0 º 10 º -10 º -20 º 20 º -30 º 30 º -40 º 40 º -50 º 50 º

  10. Sound localization error is lower using 2 CIs compared with 1 Unilateral CI Bilateral CI Normal: 6.7° Bilateral: 25.3° Unilateral: 77.7° Mean RMS Localization Errors Jones et al. (Litovsky lab)

  11. Localization with CIs is much poorer than normal hearing listeners Unilateral CI Bilateral CI Normal: 6.7° Unilateral: 77.7° Normal hearing Mean RMS Localization Errors Jones et al. (under preparation)

  12. Sound Localization in 5-12 yr. olds

  13. RMS error: Sound Localization in 5-12 yr. olds Normal Hearing BiCI GAP NH vs. CI Unilateral Bilateral Litovsky and Godar (2010) Grieco-Calub and Litovsky (2010) Review; Litovsky (2011)

  14. Testing “toddlers”: (2-3 years old) Left/Right Discrimination Orienting to sound Grieco-Calub, Litovsky, Werner (2008) Grieco-Calub & Litovsky (2012)

  15. Right – Left Discrimination (MAA) ????? 10 unable To perform the task With Uni CIs Unable to perform the task Experience with Bilateral CIs < 12 months > 12 months Normal Hearing Bilateral CIs Grieco-Calub, Litovsky, Werner (2008) Grieco-Calub & Litovsky (2012)

  16. Toddlers: Reaching for sound(Ecologically / motivating task) Stimulus When I hide I say… Litovsky et al. (2012, in press)

  17. Results • All toddlers tested with the “Reaching for sound” test were able to discriminate Left vs. Right. • However, their ability to localize was poorer than normal-hearing toddlers. • ? Do they simply not have a well developed map of space? • ? Are the processors not providing them with ideal cues for localizing?

  18. Some factors affecting performance Signal processing compromises acoustic cues Behind-the-ear (BTE) location of microphones Location of electrode within the cochlea Neural pathway degradation Difference in the insertion of electrodes between ears

  19. Brain “Plasticity” • In order for cochlear implants to be able to work, the brain has to adapt to new information, to convert electrical signals to meaningful everyday sounds (speech, music, etc.). • Plasticity is the brain’s ability to change, re-organize, respond to new information.

  20. Experience, plasticity…… Later-onset deafness Spatial map emerges or re-emerges Deaf Unilateral Bilateral Birth (deaf) 1st CI 2nd CI Hearing age Length of Bilateral Experience Chronological age at CI1

  21. “Plasticity” • Depends on history, etiology. • Depends where in the brain we look. • More plasticity at “higher” centers. More hard-wired at lower centers (training may be critical). • Important to get the peripheral information to be as good as it can be.

  22. Other sources of limitations: • Today’s CIs are Bilateral Because…. The CIs in the two ears function independently.  No guarantee that stimuli will activate devices such that ITDs or ILDs are preserved with fidelity • Goal: to provide Binauralhearing

  23. Next Step: Reverse Engineering Using Research Processors Using a Personal Digital Assistant (PDA) to load binaural software and interface with a binaural “card” for hardware (in collaboration with UT Dallas). Research processors provided by CI manufacturers to control inputs to the two ears “at the bench”

  24. Final note: Bottom-up & Top-down • What about other sources of variability? • Cognitive • Executive function • Memory • Incidental learning • How does brain plasticity interact with these? Misurelli and Litovsky, in prep.

  25. Conclusions • We are looking to close the gap between bilateralCI users and NH binaural listeners. • Optimizing localization in bilaterally implanted children may require experience with binaural cues. • Cognition and top-down processes may play an important role.

  26. Thanks to the Binaural Lab Univ. of Wisconsin Madison Waisman Center Work funded by NIH-NIDCD R01-DC003083 & R01-DC008365

  27. Exp. 1: Discriminating Right vs. Left • Child only sees 2 holes in curtain: • +/- 60 • +/-45 • +/-30 • +/-15 Test at each pair to determine if child can:  discriminate Left vs. Right  bilaterally vs. unilaterally Litovsky et al. (2012, in press)

  28. Even though they can discriminate L-R, BiCI toddlers find it harder than NH toddlers * * Litovsky et al. (2013)

  29. Exp. 2: Localizing (9 alternative forced choice) Children with Normal Hearing

  30. Exp. 2: Localizing (9 alternative forced choice) Children with Normal Hearing

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