The effect of click rate on ABR stability measured with the REPs/ABR protocol.

Abstract

Previous studies reported to this Society regarding our repeated evoked potentials (REPs) protocol for auditory brainstem responses (ABRs) have used a click rate of approximately 11 per s. Revisions in the REPs/ABR protocol requiring collection of as many as 16 waveforms in a single session encourage test streamlining, such as increasing click rate. The ABR literature suggests that while click rates of 30/s and above may affect 11/s-based absolute ABR parameters such as peak latency and peak amplitude, fewer changes will be seen with rates lower than 30/s. There are no data on the effect of click rate on ABR peak stability, the dependent variable targeted by the REPs procedure. Eight young adults with normal hearing (four women and four men) were tested in a within-subjects five-session design. Each session involved collection of 4 left ear, 4 right ear, and 8 binaural ABR waveforms; in sessions 1 and 5 a click rate of 11.1 per s was used; for sessions 2, 3, and 4, responses were evoked at click rates of 22.2, 33.3, and 44.4 per s, respectively. Results indicate that click rates faster than 30/s do create the most changes in 11/s-based peak latency and amplitude, though the effects for all increases are differentially distributed by peak, ear condition, and individual subject. Changes in click rate also have marked effects on ABR stability, both latency and amplitude, with details highly specific to individuals. In general, however, changes in stability as a function of click rate occur in the context of replication of the overall shape of the ‘‘stability profile’’ for each subject, providing further evidence of the ‘‘fingerprint’’ nature of this means of characterizing individual auditory brainstems.