Pitch Contour Following Response (PCFR) in Infants

1. Pitch Contour Following Response (PCFR) in Infants By: Elizabeth Schnabel Advised By: Dr. Jeng

2. Introduction • Voice pitch is an important auditory perception that reflects the brain’s ability to discriminate the pitch contour of speech signals.

3. FFR – Frequency Following Response • Evoked neural response from the brainstem which is phase locked to the periodicity/pitch of the stimulus harmonics. • Especially the Fundamental Frequency • Series of sinusoidal peaks – intervals between peaks reveals the pitch information of the stimulus (Moushegian et al., 1973) Frequency=1/sec =.002 sec 1/.002 =500Hz

4. Recent Studies Krishnan et al. 2004, Krishnan et al. 2005, and Swaminathan et al. 2008. Investigated: FFR’s ability to follow a harmonic pitch contour in a stimulus - Pitch Contour Following Response (PCFR) Major findings: • It was feasible to record PCFR in adults. • Native speakers of Mandarin have greater pitch strength and more accurate pitch tracking • yi2 and yi3 have greater pitch strength Krishnan et al. (2004) Time (ms)

5. Purpose • Further define the characteristics of the PCFR and its developmental trajectory • Facilitate a better understanding of how infant discriminate pitch changes during the critical period of language acquisition.

6. Questions (1) What is the feasibility of recording PCFR from individual infants? (2) How does age relate to the PCFR response? (3) How does infant response compare to adult response?

7. Methods - Participants • 9 Adults • Age range: 23-28 years • Mean ± SD = 24.2 ± 2.0 years • 7 Infants • Age range: 1-11 months • Mean ± SD = 4.86 ± 3.48 months Methods - Stimulus • Voiced Mandarin Chinese syllable • Rising lexical pitch contour: /yi/ meaning ‘aunt’.

8. Methods- Protocol • One session • Consent form reviewed and signed • Normal hearing established • Adult: Air Conduction <20dB between 250-8000Hz • Infant: Distortion Product Otoacoustic Emissions - 2000-8000 Hz. • Electrode/ear tip placement • State of restfulness was achieved • Stimulus and recording started • Two trials of 1200 tokens • Two trials of 1200 control

9. Results • Spectrograms • Pitch Strength - Amplitude • Latency

10. Results • Typical Spectrograms • Show spectral energy bands which can reflect harmonic pitch change over time.

11. Results • Spectrograms of all Infants

12. Discussion - Spectrogram • Visual representation of the infants ability to follow pitch contour over time. • The feasibility of recording PCFR in individual infants as early as one month of age

13. Results • Pitch Strength - Autocorrelation - correlating the response to itself • Estimation of pitch period • Estimation of response pitch strength • peak to trough amplitude Stimulus

14. Results • Amplitude: Pitch strength

15. Discussion – Pitch Strength • Consistent with Gardi et al. (1979) - Compared tone-burst elicited FFR in 22 neonates (<3 days old) and the average adults responses from his doctoral dissertation. • line of best fit suggests that the neonates had a larger amplitude at 55dBnHL compared to adults at 250 Hz tone burst

16. Discussion – Pitch Strength cont. • Larger amplitude could also be contributed by: • Infants smaller head size • Infant small ear canal volume

17. Results • Latency - Cross correlation between the stimulus and recording

18. Discussion - Latency • Gardi et al. (1979) • Consistant – Longer latencies as frequency decreases • Difference – Gardi et al. had a significant difference between infant and adult latencies at low frequencies. p=0.0813

19. Conclusion (1) It is feasible to record a PCFR in individual infantsas early as one month of age. (2) Further data is needed to be obtained from more infants to better delineate the developmental trajectory of infant PCFR. (3) There is significant difference between the mean of infant and adult pitch strength amplitude.

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