Electrophysiological and morphological changes in the Guinea pig cochlea following mechanical trauma to the organ of corti

Small discrete lesions were produced in the organ of Corti of the guinea pig cochlea using fine probes to produce direct mechanical insult. The electrophysiological state of the cochlea was assessed using N, electro-cochleography and loss of receptor cells determined by scanning electron microscopy. Principal findings were: 1) Excellent agreement between the location of hair cell losses and the frequency of maximum sensitivity change in the N, audiogram; 2) The spatial extent of the mechanically induced lesion appears to be more important than the total number of hair cells lost, in determining the magnitude of N, sensitivity loss; 3) Hair cell losses extending over only 72 ixm could be detected as significant changes in N, sensitivity. These results further emphasize the accuracy and usefulness of the N, electrocochleo-gram for assessing the functional status of the cochlea; 4) Lesions involving only outer hair cell loss also produced marked elevations of N, threshold.