Cortical Auditory-Evoked Potentials in Response to Multitone Stimuli in Hearing-Impaired Adults

To determine if one-octave multitone (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-band noise (NBN).

CAEPs were obtained from 16 hearing-impaired 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. Auditory stimuli were monaurally delivered through insert earphones at 10 and 20 dB above threshold. The root mean square amplitude of the CAEP and the detectability of the responses using Hotelling's T² were calculated and analyzed.

CAEP amplitudes elicited with MT stimuli were on 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 when 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 20 dB SL, and was comparable with detection sensitivities observed in normal-hearing participants.

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.