Surface-recorded cochlear microphonic potentials during temporary threshold shifts in man

Abstract

Cochlear microphonic potentials (CM) were recorded, by means of surface electrodes, before, during and after white-noise-induced temporary threshold shifts (TTS) in human volunteers. The behavioural threshold shift was not accompanied by a change in amplitude of CM. These findings indicate that in humans, the site affected by the noise exposure and which probably gives rise to the TTS is central to the site of generation of CM. In a previous study, the compound action potential generated in the auditory nerve was found to be of lower amplitude and longer latency during TTS, and it is thus proposed that the site affected is peripheral to the generation of conducted action potentials. The synapse between hair cells and the auditory nerve fibres is the most likely candidate to be the affected site.

Key Words:

• Temporary threshold shift
• Cochlear microphonics
• Human electric responses
• Noise