[Stimulus level dependence of BERA potential amplitudes].

The observed stimulus level dependence of early acoustic evoked potential amplitudes suggests that two different mechanism contribute to neural activity: A first mechanism yields neural activity immediately above the hearing threshold, the activity increasing up to a maximum value which is attained at a stimulus intensity of approximately 40 dB HL. At this level, the onset of a second mechanism is observed, which produces increasing neural activity and exhibits saturation behaviour at high stimulus intensities. A mathematical amplitude intensity characteristic is presented which can be calculated on the basis of simple and plausible assumptions. It is in excellent agreement with the experimental data. Furthermore, in the case of damaged hair cells but undamaged nerve fibres, the mathematical approach leads directly to the steep amplitude characteristic as it is often observed in the case of recruitment.