Effects of audiometric configuration on the auditory brain stem response.

Evidence reported in the literature indicates that wave I of the auditory brain stem response is influenced by cochlear contributions from a more basal area of the cochlea than is wave V. This phenomenon is invoked to explain different latency-intensity function patterns of waves I and V and the I-V interval for four types of cochlear hearing loss. In high frequency hearing losses wave V is delayed at low intensities. Wave I tends to be delayed at all intensities and by a greater amount than wave V. The I-V interval is often reduced with the effect maximal at higher intensities. Low frequency hearing losses tend to cause early wave V latencies at low intensities. Wave I latencies are normal. The I-V interval is therefore reduced at lower intensities. Flat hearing losses produce normal latency-intensity functions. High frequency notched audiograms are almost always associated with delayed wave V but early wave I latencies. The I-V interval is therefore significantly prolonged with the effect maximal at low intensities. The variability of the I-V interval as a function of audiometric configuration indicates that it is not a pure measure of central conduction time.