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Improving Adaptation to Basalward Shift for Speech Perception in CI Users

Improving Adaptation to Basalward Shift for Speech Perception in CI Users. T. M. Talavage 1 , M. A. Svirsky 2 , E. Haneda 1 , H. Neuburger 2 1 Purdue University, West Lafayette, IN 2 Indiana University/Purdue University Indianapolis, Indianapolis, IN. Motivation.

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Improving Adaptation to Basalward Shift for Speech Perception in CI Users

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  1. Improving Adaptation to Basalward Shift for Speech Perception in CI Users T. M. Talavage1, M. A. Svirsky2, E. Haneda1, H. Neuburger2 1Purdue University, West Lafayette, IN 2Indiana University/Purdue University Indianapolis, Indianapolis, IN

  2. Motivation • Cochlear implant (CI) users experience variable speech perception performance • Asymptotic level depends upon subject • Time required to achieve asymptotic level on order of months, years • CI known to introduce specific “unnatural” signal alterations • Loss of resolution • Basalward (upward) shift of frequency

  3. 20Hz 1kHz 2kHz 4kHz 8kHz Ideal position Typical position 250Hz 6.8kHz Insertion direction 1 2 3 4 5 6 7 8 800Hz 11kHz 1 2 3 4 5 6 7 8 5-8 mm shift Sources of Signal Alterations

  4. The Hypothesis Gradual introduction of the basalward shift will enhance use of those speech perception pathways developed prior to onset of deafness and accelerate adaptation to cochlear implant stimulation.

  5. Justification for Hypothesis • Problems associated with abrupt shift • Misalignment of input/sensed frequencies • “Pattern recognition” thrown off by mismatch • Proposed benefits of gradual shift • Use pre-existing speech perception pathways • Less “relearning” • Asymptotic levels not expected to change

  6. Treatment #1 Training Testing fMRI Evaluation Treatment #2 Training Testing fMRI Investigation of Basalward Shift • Evaluate adaptation to shift for two rehabilitation procedures: • Standard (STD) Treatment • Full frequency shift used from the beginning. • Experimental (EXP) Treatment • Full frequency shift gradually introduced over multiple training sessions.

  7. Pilot Investigation • 6 volunteer subjects • 3 per treatment group (STD, EXP) • Matched pairs (pre-test) • All female, 5 left-brain dominant • 15 perceptual training/testing sessions • One hour duration • Limit on gap between sessions • 3 fMRI sessions • Two hour duration • Conducted after 0th, 7th/8th and 15th sessions

  8. Cochlear Implant Acoustic Simulator • Real-time noise-band simulator (Kaiser and Svirsky, 2000). • Simulates 8 electrodes • 8 movable analysis (input) filters • 8 fixed synthesis (output) filters • Enables use of normal-hearing (NH) subjects for training and testing. • fMRI compatibility • Subject safety

  9. 10000 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 Synthesis Filters (Output) 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Frequency (Hz) 1000 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 6.5 mm shift 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Analysis Filters (Input) 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Session number Standard treatment (Fixed shift)

  10. 8 8 7 10000 7 6 6 8 8 8 8 8 8 8 8 8 8 8 8 8 8 5 5 Synthesis Filters (Output) 7 7 7 7 7 7 7 7 7 7 7 7 7 7 4 4 6 6 6 6 6 6 6 6 6 6 6 6 6 6 3 3 5 5 5 5 5 5 5 5 5 5 5 5 5 5 2 2 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Frequency (Hz) 1000 1 1 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 6.5 mm shift 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Analysis Filters (Input) 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Session number Experimental treatment (Gradual shift)

  11. Perceptual Training/Testing • Vowel identification • 48 tests from 9 vowels • Consonant identification • 48 tests from 16 consonants • CID (Central Institute of Deaf) sentence test in every 4th sessions • 20 sentences • Speech tracking • Two 10 min sets of discourse tracking with audiovisual feedback

  12. consonants (average data) vowels (average data) 100 100 80 80 60 60 percent correct percent correct 40 40 20 20 0 0 P1 P2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 P1 P2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 session session speech tracking (average data) cid sentences (average data) 100 100 80 80 60 60 percent correct standard words per minute 40 experimental 40 20 20 0 0 P1 P2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 session session Pilot Results (Perceptual Testing) Data courtesy of Dr. Mario Svirsky

  13. fMRI – Experimental Parameters • 1.5 Tesla GE LX (Indiana University School of Medicine, Indianapolis, IN) • 15 slices (voxel size: 3.75mm x 3.75mm x 3.80mm) • Clustered volume acquisition (Edmister et al. 1999) • Stimuli • Forward or time-Reversed speech • CNC words (e.g. jail, sail, duck) • Three stimulus classes • NS: Normal speech (unaltered) • HS: Half-Shift speech (~3mm simulated shift) • FS: Full-Shift speech (~6mm simulated shift) • Stimulus Presentation • Subjects wear ear plugs under ear muffs

  14. Rev Rev Rev For Rev For For For 0 4 12 100 Number of image acquisition Trial structure within TR Word #1 Word #2 Image acquisition(1500 ms) 3400 ms 700 ms 700 ms 200 ms Stimuli Response period fMRI – Experimental Parameters

  15. fMRI Data Analysis • AFNI (afni.nimh.nih.gov) used for all analysis • Calculate % signal difference • Calculate correlation-coefficient • Conducted in Talairach co-ordinates (Talairach and Tournoux, 1988) • Group analyses • Comparison of Forward and Reverse • Forward (NvsF) • Reverse (NvsR) • Contrast (FvsR) • Comparison of STD vs. EXP treatment • ANOVA across sessions and subjects within group

  16. fMRI Results – Quick Summary • Normal Speech (NS) • Neither group exhibits dependence on session • Half-shift Speech (HS) • EXP exhibits dependence on Session(ANOVA: p < 0.05) • Wernicke’s area (posterior BA 22) • Broca’s area (BA 44&45) • STD does not exhibit statistically significant trend • Full-shift Speech (FS) • EXP exhibits dependence on Session(ANOVA: p < 0.05) • Wernicke’s area (posterior BA 22) • Broca’s area (BA 44&45) • STD does not exhibit statistically significant trend

  17. EXP group STD group EXP group STD group fMRI Results – ANOVA Full-shift Speech (FS) Half-shift Speech (HS) BA 22 BA 44 Displayed activity significant to the p < 0.05 level (ANOVA)

  18. EXP group STD group Wernicke’sarea Broca’sarea % Signal Change Results – NS

  19. % Signal Change Results – HS EXP group STD group Wernicke’sarea Broca’sarea

  20. % Signal Change Results – FS EXP group STD group Wernicke’sarea Broca’sarea

  21. Discussion • Gradual introduction of the frequency shift may benefit CI user rehabilitation • Perceptual data indicate more rapid adaptation • fMRI data indicate greater differentiation of response to Forward and Reverse speech with training • Increase in FvsR difference correlates with training experience • fMRI can be a useful, complementary technique to evaluate novel CI rehabilitation schemes • “Next Step” • ...more linguistically demanding task • ...increase N

  22. Acknowledgments • This work partially funded by • American Hearing Research Foundation • Indiana University School of Medicine • Purdue Research Foundation • National Institutes of Health • NIDCD • NIBIB

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