Characterizing Electrophysiological Response Properties of the Peripheral Auditory System Evoked by Phonemes in Normal and Hearing Impaired Ears.

Abstract

This study aimed to characterize time and spectral domain characteristics of the phoneme-evoked electrocochleography (ECochG) response and explore potential associations between the ECochG spectral content, word recognition scores (WRSs), residual hearing, and aging in normal and hearing-impaired listeners. This was a prospective study with 25 adult participants. All participants underwent intraoperative ECochG testing and responses were recorded from the round window niche. Participants were divided into two groups based on their preoperative pure tone average: normal/mild sensorineural hearing loss and moderate/moderately-severe sensorineural hearing loss. Target stimuli were a 40 ms /da/ and an 80 ms /ba/ presented in alternating polarity (rarefaction/condensation). Waveform response patterns were analyzed including amplitude, latency, and spectra. Structural similarity index measure (SSIM) was used to determine similarity between the stimulus spectrum and that of the ECochG differential waveform. Correlation analyses were carried out among pure tone average, SSIM, age, and WRS. ECochG alternating waveform morphology evoked by the /da/ stimulus consisted of five prominent peaks labeled N 1 -N 5 . Its spectrum was dominated by the fundamental (F 0 ) frequency. The ECochG alternating response evoked by /ba/ consisted of nine prominent peaks labeled N 1 -N 9 and was also dominated by F 0 . Amplitudes and latencies were not statistically different between groups for both stimuli. Significant positive correlations were found between SSIM and WRS for responses evoked by /da/ (r = 0.56) and responses evoked by /ba/ (r = 0.67). High frequency pure tone average and the /ba/ SSIM were found to have a significant negative correlation (r = -0.58). Speech-like stimuli have become increasingly utilized in the assessment of auditory function. Here, we provided the groundwork for understanding how commonly employed syllable stimuli are encoded by the peripheral auditory system in regard to temporal and spectral characteristics. Expanding this work to include measurements of central auditory processing in conjunction with cochlear physiology is warranted to further understand the relationship between peripheral and central encoding of speech-like stimuli.