Electrocochleography and Recruitment

Electrocochleography was performed in about 80 recruiting ears, including Ménière ears and ears showing hearing loss due to asphyxia, noise trauma, or the use of ototoxic drugs. Criteria for recruitment detection on the basis of electrocochleography were investigated by means of the description of action potential waveforms, slopes of action potential input-output curves, and latency-intensity functions. The validity of two models for the mechanism of loudness recruitment is discussed in relation to data obtained from narrow-band response contributions to the compound action potential in response to tonebursts. A relationship was found between the shape of the AP input-output curve for toneburst stimulation and the shape of the response area, which favors the recruitment model recently proposed by Evans. This justifies use of the slope of the input-output curve as an indicator for the presence of loudness recruitment, and additional support is provided by the latency at near-threshold values. The AP waveform seems to have pure illustrative interest.