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

R. KRISHNAN,PhD, Audiology

Previous Work

(PET, fMRI, FFR)

Cerebral Cortex Auditory Brainstem

Current Work

IRN (nonspeech stimuli; static vs. dynamic)

Sti

mu

lus

Res

po

nse

IRN block diagram

IRN continuum

Speech/Nonspeech

Delayd

Gaing

+ Delayd

Gaing +

Output, y(t)

• 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

Chinese tone contrasts

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100110120130140

0 50 100 150 200 250708090

100110120130140

0 50 100 150 200 250708090

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Time (ms)

T1-T3

T1-T2

T2-T3

Am

pli

tud

e (m

icro

vo

lts) -4

-3

-2

-1

0

1

2

-4

-3

-2

-1

0

1

2

-100 0 100 200 300 400 500-4

-3

-2

-1

0

1

2

Time (ms)

MMN Response

T1-T3

T1-T2

T2-T3

F0

(Hz)

CE

CE

Current WorkMMN (Speech stimuli; Chinese vs. English)

CE

Future Directions

• 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

(i) 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

(ii) 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

(iii) domain specificity … by using novel iterated ripple noise stimuli whose temporal regularity is systematically controlled

(iv) laterality … by comparing pitch representation for right and left ear stimulation SPECIFIC AIMS

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