Auditory Steady State Responses in Normal-Hearing and Hearing-Impaired Adults
Contact Name: Dr Tim Wilding
Contact Email: email@example.com
Tim started his training and career in audiology after first working for a number of years as an electronic engineer designing ICs (“computer chips”) for consumer electronic devices. He then went on to obtain a BSc and PhD in Audiology at the University of Manchester where he is now a teaching focused lecturer. His research activities to date have examined: using the ASSR for dead region diagnosis, possible advantage of classroom FM system use, and classroom acoustics measures. He is an RCCP registered audiologist and keeps his clinical skills up to date by working in NHS adult hearing aid clinics whenever possible.
Objectives: The aim of this study was to assess the between-session repeatability of auditory steady state response (ASSR) amplitudes and to examine F ratio response detection parameters.
Design: Supra-threshold ASSRs were recorded from 20 normal-hearing and 10 hearing-impaired subjects. Amplitudes and latencies were recorded in two test sessions conducted on separate days.
Analysis: The repeatability coefficients (limits of expected variation in repeat measurements) for amplitude and latency of ASSRs were calculated. The test time required for the responses to reach significance at 1%, 2%, and 5% F ratios was analysed. The percentage false response detection rate was calculated to determine the suitability of current ASSR threshold estimation protocols for use in audiology clinics.
Results: The repeatability coefficients for the amplitude of ASSRs were 29 nV for the normal-hearing subjects and 57 nV for the hearing-impaired subjects. The repeatability coefficients for the latency of ASSR were 1.10 msec for the normal-hearing subjects and 1.19 msec for the hearing-impaired subjects. High false-positive detection rates were found for detection procedures that used variable test time (“stop when significance reached” methods).
Conclusions: The results of this study showed that ASSR amplitudes are highly variable between test sessions with an average estimated variability in response amplitude of ±40% for normal-hearing participants and ±97% for hearing-impaired participants. This could be a possible cause of test–retest differences in ASSR threshold measurements, as it could potentially lead to thresholds that were above the EEG noise level and significant in one test session subsequently falling below the EEG noise level in the repeat test session leading to insignificant response and thus poorer ASSR threshold.
Wilding et al. (2012) Ear and Hearing 33:267-278