1. 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

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 comprehensionLanguage expression Niparko et al. (2010)

6. Our recent research shows that: 1) Language perception: most children are within 1 SD of mean 2) Language production: >50% children +/- 1SD; some are below Language comprehension Language expression

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

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

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

12. Sound Localization in 5-12 yr. olds

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

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

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

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…… DeafUnilateralBilateral Chronological age at CI1 Length of Bilateral Experience Hearing age Birth (deaf) 1 st CI2 nd CI Later-onset deafness Spatial map emerges or re-emerges

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 Binaural hearing

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 1.We are looking to close the gap between bilateral CI users and NH binaural listeners. 2.Optimizing localization in bilaterally implanted children may require experience with binaural cues. 3.Cognition and top-down processes may play an important role.

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

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