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Characteristics of Speech-Evoked Envelope Following Responses in Infancy
Trends in Hearing
  • Vijayalakshmi Easwar, University of Wisconsin-Madison
  • Susan Scollie, The University of Western Ontario
  • Michael Lasarev, University of Wisconsin-Madison
  • Matthew Urichuk, The University of Western Ontario
  • Steven J. Aiken, Dalhousie University
  • David W. Purcell, The University of Western Ontario
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Envelope following responses (EFRs) may be a useful tool for evaluating the audibility of speech sounds in infants. The present study aimed to evaluate the characteristics of speech-evoked EFRs in infants with normal hearing, relative to adults, and identify age-dependent changes in EFR characteristics during infancy. In 42 infants and 21 young adults, EFRs were elicited by the first (F1) and the second and higher formants (F2+) of the vowels /u/, /a/, and /i/, dominant in low and mid frequencies, respectively, and by amplitude-modulated fricatives /s/ and /∫/, dominant in high frequencies. In a subset of 20 infants, the in-ear stimulus level was adjusted to match that of an average adult ear (65 dB sound pressure level [SPL]). We found that (a) adult–infant differences in EFR amplitude, signal-to-noise ratio, and intertrial phase coherence were larger and spread across the frequency range when in-ear stimulus level was adjusted in infants, (b) adult–infant differences in EFR characteristics were the largest for low-frequency stimuli, (c) infants demonstrated adult-like phase coherence when they received a higher (i.e., unadjusted) stimulus level, and (d) EFR phase coherence and signal-to-noise ratio changed with age in the first year of life for a few F2+ vowel stimuli in a level-specific manner. Together, our findings reveal that development-related changes in EFRs during infancy likely vary by stimulus frequency, with low-frequency stimuli demonstrating the largest adult–infant differences. Consistent with previous research, our findings emphasize the significant role of stimulus level calibration methods while investigating developmental trends in EFRs.

Citation Information
Vijayalakshmi Easwar, Susan Scollie, Michael Lasarev, Matthew Urichuk, et al.. "Characteristics of Speech-Evoked Envelope Following Responses in Infancy" Trends in Hearing Vol. 25 (2021)
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