[Relationship between cochlear fatigue and the asymmetrical non-linearity of microphonic responses in the guinea pig...

It is classically considered that cochlear fatigue and acoustic trauma occur when intensity is such that the ear is saturated, i.e. when the microphonic potential fails to increase in a linear fashion in relation to intensity and when distorsion appears. The present report concerns a study in the guinea pig of the relationship between the non-linearity of microphonic responses, and their fatigability. The results show that fatigability is related not only to non-linearity but also to the asymmetry of responses. The asymmetry of microphonic responses may be interpreted as reflecting an asymmetrical ionic flow at the upper pole of hair cells, resulting in an accumulation of potassium ions within and around hair cells and thereby creating a depression of responses.