The results indicate that latency measures are more sensitive indicators of the early effects of decreased audibility than are response strength (amplitude, d' or percent correct) measures. Sensorineural hearing loss has a greater impact on higher level or "nonsensory" cortical processing in comparison with lower level or "sensory" cortical processing. Possible physiologic mechanisms within the cortex that may be responsible for these response changes are presented. Lastly, the possible clinical significance of these ERP and behavioral findings is discussed.

This review paper briefly considers how stimulus, noise masking and recording parameters affect the frequency and place specificity of auditory brainstem responses (ABRs) to air- and bone-conducted stimuli. Issues concerning the use of clicks for ABR threshold estimates will first be presented, followed by results for tone-evoked ABR thresholds and how well they predict the pure-tone behavioral audiogram. Noise-masking options (e.g. high-pass noise, notched noise and white noise) to improve the frequency specificity of tone-evoked ABRs, which are now available on clinical ABR units, will also be discussed. The goal of this article is to demonstrate that ABRs to tonal stimuli can be successfully recorded in most clinical environments and can provide reasonably accurate estimates of 500-to 4000-Hz pure-tone behavioral thresholds in infants, children and adults. Specific parameters and protocols for obtaining frequency-specific ABR threshold responses are provided.

This study investigated the frequency specificity of the auditory brainstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz brief tones using narrow-band derived response analyses of the responses recorded in high-pass masking noise [Oates and Stapells, J. Acoust. Soc. Am. 102, 3597-3608 (1997)]. Stimuli were linear- and exact-Blackman-gated tones presented at 80 dB ppe SPI. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by response amplitude profiles as a function of derived band center frequency. The largest amplitudes of waves V and Na-Pa occurred in the 500- and 707-Hz derived bands in response to the exact-Blackman- and linear-gated 500-Hz tones. The peak in the response amplitude profiles for wave V to both 2000-Hz stimuli was seen in the 2000-Hz derived band. For wave Na-Pa, the maxima in the amplitude profiles occurred in the 2000- and 1410-Hz derived bands for the exact-Blackman- and linear-gated tones. Smaller cochlear contributions to the ABR/MLR were also present at 0.5-1 octave above and below the nominal stimulus frequencies. The ABR/MLR to 500- and 2000-Hz 80 dB ppe SPL tones thus shows good frequency specificity, with no significant differences in the frequency specificity of: (1) ABR versus MLR; (2) these evoked potentials to 500-versus 2000-Hz tones; and (3) responses to exact-Blackman- versus linear-gated tones.