Recording from the inferior colliculus following cochlear inner hair cell damage.

The anti-cancer drug carboplatin has been used to generate inner hair cell (IHC) lesions in the cochleae of chinchilla. This model has provided a valuable physiological tool for the study of the auditory system, particularly concerning the relative roles of IHCs and outer hair cells (OHCs). We recorded responses to contralateral sound stimuli of single units (SU) in the central nucleus (CN) of the inferior colliculus (IC) from normal and carboplatin treated animals. Normal single unit thresholds and frequency tuning curves (FTCs) were found, despite gross IHC damage within the cochleae of carboplatin treated animals. No evoked afferent responses could be detected in CN regions which represented cochlear loci where total IHC loss had occurred. Normal frequency selectivity in the auditory system is possible with small numbers of surviving IHCs provided OHCs remain normal.