Comparison of peripheral compression estimates using auditory steady-state responses (ASSR) and distortion product otoacoustic emissions (DPOAE)

Description

Title
Comparison of peripheral compression estimates using auditory steady-state responses and distortion product otoacoustic emissions

Background
The healthy auditory system shows a compressive input/output function, commonly assumed to be a result of healthy outer-hair cell function. Hearing impairment often leads to a decrease in sensitivity and a reduction of compression. Compression estimates in human listeners are commonly based on psychoacoustical procedures, or on measurements of otoacoustic emissions (OAEs). Psychoacoustical procedures are time consuming and rely on assumptions regarding the ability to selectively investigate cochlear processing. OAEs allow to selectively study cochlear processing, but the interpretation of results based on individual data is challenging. Auditory steady-sate responses (ASSR) represent a method allowing fast, reliable and frequency-specific objective measurements of hearing function. In the present study it is investigated if ASSR can be used to estimate compression along the peripheral auditory pathway. It is hypothesized that compressive behaviour is observed in normal-hearing (NH) listeners while in hearing-impaired (HI) listeners, sensitivity and compression are reduced. ASSR data are compared to compression estimated using distortion-product otoacoustic emissions (DPOAEs).

Methods
ASSR were measured using 64-channel EEG with active electrodes. Input-output functions were obtained for NH and HI listeners using multi-frequency stimulation with four sinusoidally amplitude modulated tones (sAM) at carrier frequencies from 500-4000 Hz and modulation frequencies between 80 and 100 Hz. The input level was varied between 20 and 80 dB SPL in steps of 5 dB. Results were compared to compression estimates from DPOAEs within the same listeners.

Results
The data show that ASSR growth functions can be measured in NH listeners for input levels between 20 and 80 dB SPL. Strong compression was found for input levels of 20-30 dB SPL and higher. For HI listeners, the results show a larger variability compared to NH listeners. Reliable responses could only be obtained for levels corresponding to about 30~dB SL and above. The compression estimates obtained with ASSR were larger than those obtained using DPOAE.

Conclusions
ASSR could be used to estimate peripheral compression simultaneously over a large frequency range. For HI listeners, compression estimates are possible for levels corresponding to 30 dB SL and above. ASSR might be a method for fast and reliable estimates of peripheral input-output functions and hence the state of the active process in the inner ear.

Funding
This work was funded by the Oticon Center of Excellence for Hearing and Speech

Period	22 Feb 2014 → 26 Feb 2014
Event title	37th Annual MidWinter Meeting of the Association for Research in Otolaryngology
Event type	Conference
Conference number	37
Location	San Diego, CA, United StatesShow on map
Degree of Recognition	International