1. R. KRISHNAN, PhD, Audiology J. Gandour, PhD, Linguistics B. Chandrasekaran, MS, Speech & Hearing J. Swaminathan, MS, Electrical Engineering • Long term goal is to understand the nature of experience-dependent pitch representation at the brainstem level • How pitch processing emerges from differential demands on auditory and linguistic processes • Vary listeners: Mandarin Chinese, Thai, English • Vary stimuli: speech/nonspeech (IRN); pitch contours

2. Previous Work (PET, fMRI, FFR) Cerebral Cortex Auditory Brainstem

3. Output, y(t) Delay d Gain g Delay d Gain g + + Current Work IRN (nonspeech stimuli; static vs. dynamic) IRN block diagram Stimulus Speech/Nonspeech Response IRN continuum

4. C E Current Work MMN (Speech stimuli; Chinese vs. English) MMN Response Chinese tone contrasts 140 2 130 1 120 • Does language experience modulate the preattentive processing of linguistically-relevant pitch contours? • Mismatch negativity mean amplitude reflects earliest levels of change detection in the cortex • MMN mean amplitude C>E: Early cortical processing of linguistic tones is facilitated by language experience • T2-T3 < T1-T2, T1-T3 in Chinese: Tonal space is shaped by language-specific phonological rules 0 110 100 -1 90 -2 T1-T3 T1-T3 80 70 -3 0 50 100 150 200 250 -4 F0 (Hz) 2 140 130 1 Amplitude (microvolts) 120 0 110 100 -1 90 -2 C E T1-T2 T1-T2 80 -3 70 0 50 100 150 200 250 -4 2 140 130 1 120 0 110 -1 100 90 -2 C E T2-T3 T2-T3 80 -3 70 0 50 100 150 200 250 -4 -100 0 100 200 300 400 500 Time (ms) Time (ms)

5. Future Directions • linguistic sensitivity of this pitch representation by using stimuli changing in lexical status, direction of pitch change, and degree of similarity in the pitch contours • tonal specificity … by using stimuli that either deviates in pitch contour from the lexical prototype of a given language or moves from one native phonetic prototype to another • domain specificity … by using novel iterated ripple noise stimuli whose temporal regularity is systematically controlled • laterality … by comparing pitch representation for right and left ear stimulation SPECIFIC AIMS • develop non-invasive measures for multilingual population in USA and changes in pitch representation after retraining of hearing-impaired listeners • develop optimal, language-sensitive signal processing strategies for conventional hearing aids and/or cochlear implants used by hearing-impaired listeners PUBLIC HEALTH