“The Effects of Selective Hair Cell Damage on Temporal Envelope Coding in the Auditory Nerve.” Michael G. Heinz, Ph.D., Purdue University, West Lafayette, Indiana.

This project involves the collection of auditory-nerve fiber responses to amplitude modulated sounds from chinchillas. Responses are to be compared between animals with normal hearing and animals with sensorineural hearing loss arising from either selective outer-hair-cell or inner-hair-cell damage. A fairly complete set of data has been collected from normal-hearing chinchillas and the researchers are now collecting data from animals with selective hair-cell damage for this pilot study.

Selective outer-hair-cell damage is induced through administration of kanamycin (an antibiotic used to treat infections) over a several-week period, whereas selective inner-hair-cell damage is induced with administration of carboplatin (a chemotherapy drug used against some forms of cancer). A major goal of this pilot study is to settle on dosage protocols in chinchillas for the configurations and degrees of hearing loss that are appropriate for studying the neural encoding of perceptually relevant sounds. Both kanamycin and carboplatin have been successfully administered to an initial set of chinchillas.

The neural data collected in this study will provide useful comparisons to data collected over the last year from chinchillas with noise-induced hearing loss, for which results are more difficult to interpret due to the typical mixed configuration of outer- and inner-hair-cell damage. A thorough understanding of the effects of hair-cell damage on temporal coding will provide useful insight for understanding the difficulties people with sensorineural hearing loss have in real-world listening environments. This insight will be useful for future development of hearing-aid strategies to overcome these difficulties.