j. gandour, phd, linguistics b. chandrasekaran, ms, speech & hearing j. swaminathan, ms,...
TRANSCRIPT
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
0 50 100 150 200 250708090
100110120130140
0 50 100 150 200 250708090
100110120130140
0 50 100 150 200 250708090
100110120130140
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
PUBLIC HEALTH