Compound Action Potential (AP) Tuning in Man and Guinea Pig: Effect of Probe Tone Level and Hearing Loss
Several studies have indicated the influence of pathology on AP tuning. In animal studies Harris (1979, chinchilla) showed that APTCs usually are broader than single fibre tuning curves at the same characteristic frequency. This was also shown by van Heusden and Smoorenburg (1981, cat). Furthermore, they concluded that after noise trauma the APTC broadens and that the use of a higher probe tone level was only partially responsible for this widening. Gorga and Abbas (1981, cat) observed that sharpness of APTCs, expressed in QlOdB, was unaffected by acoustic trauma or probe level, while the low-frequency tail could become relatively hypersensitive. Shepard and Abbas (1983, cat) correlated APTC findings to histological data from acoustically traumatized ears. They concluded that traumatized ears had a decreased sharpness of tuning and a less sensitive tip and tail region. Also, normal tuning could sometimes go along with hair cell damage. Inner hair cell damage affected the tail position, outer hair cell damage the tip region.
KeywordsTriad Crosscorrelation Pethidine Phenergan Nembutal
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