Cortical auditory evoked potentials (CAEPs) in response to multi-tone (MT) stimuli in hearing-impaired adults.
Van Dun, Bram
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Abstract Objective: To determine if one-octave multi-tone (MT) stimuli increase the amplitude of cortical auditory evoked potentials (CAEPs) in individuals with a hearing loss when compared to standard pure-tone (PT) stimuli and narrow-bands noise (NBN). Method: CAEPs were obtained from 16 hearing impaired (HI) adults in response to PT and MT auditory stimuli centered around 0.5, 1, 2 and 4 kHz and NBN centered around 1 and 2 kHz. Hearing impairment ranged from a mild to a moderate hearing loss in both ears. The auditory stimuli were monaurally delivered through insert ear-phones at 10 and 20dB above threshold. The root mean square (RMS) amplitude of the CAEP and the detectability of the responses using Hotelling’s T2 were calculated and analyzed. Results: CAEP amplitudes elicited with MT stimuli were in average 29% larger than PT stimuli for frequencies centered around 1, 2 and 4 kHz. No significant difference was found for responses to 0.5 kHz stimuli. Significantly higher objective detection scores were found for MT as compared to PT. For the 1 and 2 kHz stimuli, the CAEP amplitudes to NBN were not significantly different to those evoked by PT but a significant difference was found between MT stimuli and both NBN and PT. The mean detection sensitivity of MT for the four frequencies was 80% at 10 dB SL and 95% at 20dB SL, and was comparable with detection sensitivities observed in normal-hearing subjects. Conclusion: Using MT stimuli when testing CAEPs in adults with hearing impairment showed larger amplitudes and a higher objective detection sensitivity compared to using traditional PT stimuli for frequencies centered around 1, 2 and 4 kHz. These findings suggest that MT stimuli are a clinically useful tool to increase the efficiency of frequency-specific CAEP testing in adults with hearing impairment.