Contralateral suppression of TEOAE. Attempts to find a latency.

Abstract

Latency of the contralateral suppression of transient-evoked otoacoustic emissions (TEOAE) has been investigated using the ILO88 system for ipsilateral stimulation and recording, and a laboratory computer interface producing contralateral noise bursts. Reduction of rms amplitude in the last 10.24 ms of the response was found to produce the most consistent indication of suppression. Onset latencies varied from less than 40 ms to 140 ms, offset latency from 20 ms to more than 80 ms. Acoustic reflex latencies have not been reported with such short latencies and this makes it unlikely that this reflex can be responsible for the contralateral suppression of TEOAE. This study used contralateral stimuli at 70 dB HL. Lower level stimuli may result in increased amplitude and it is also possible that the effect of contralateral stimulation may be frequency specific. The long offset latency necessitates long intervals between stimuli with an inherent risk of variation in stimulus and recording conditions. This makes an elaborate study of the latency difficult to perform in humans.