Auditory Brainstem Encoding of Plosives in Korean Normal Hearing Listeners

Auditory Brainstem Encoding of Plosives in Korean Normal Hearing Listeners

Purpose: It is increasingly acknowledged that auditory brainstem response (ABR) elicited by speech can reflect the listener’s perceptual cues of complex sound with replicability and reliability. This study sought to identify the brainstem responses evoked by Korean syllables and to characterize any relation between acoustic features of the speech and their neurophysiological responses at the brainstem level. Methods: Thirty young adults with normal hearing who were native Korean speakers participated in the study. As speech stimuli, nine Korean syllables, i.e., a combination of nine plosives /p, p*, ph, t, t*, th, k, k*, kh/ followed by an /a/ vowel naturally produced by a male speaker, were applied for electrophysiological measure. Each waveform of the syllable was analyzed by seven peaks, V, A, C, D, E, F, and O, to determine latency, amplitude, and morphology. Results: According to transient responses, the peak V-A latencies of alveolar syllables were significantly delayed, while supporting their long voice onset time. Latencies of peak C for /ta/ and /t*a/ syllables were prolonged, having longer consonant duration. Although the latencies of peak O usually looked prolonged for the aspirate syllables, they did not support acoustic characteristics in terms of the end of voicing. In the view of sustained responses, a significant difference exists in latency for the D-E and E-F inter-peaks. However, unlike the transient response, no relation between sustain features and brainstem response was found. Conclusion: Speech-evoked ABR reflects clear and synchronized patterns of the brainstem, while providing information on the transient response regarding auditory pathway encoding of the plosive consonant portion of speech. It can provide a fundamental and biological snapshot of auditory processing that predicts auditory-based communication skills and gain.