Gap Detection Deficits in Chinchillas with Selective Carboplatin-Induced Inner Hair Cell Loss

Temporal resolution is essential for processing complex auditory information such as speech. In hearing impaired persons, temporal resolution, often assessed by detection of brief gaps in continuous sound stimuli, is typically poorer than in individuals with normal hearing. At low stimulus presentation levels, hearing impaired individuals perform poorly but the deficits are greatly reduced when the sensation level of the stimuli are adjusted to match their normal hearing peers. In the present study, we evaluated the effect of selective inner hair cell loss on gap detection in chinchillas treated with carboplatin, an anticancer drug that selectively damages inner hair cells and afferents in this species. Treatment with carboplatin-induced inner hair cell loss of ~ 70 % but had little effect on audiometric thresholds in quiet and produced no evidence of outer hair cell loss. In contrast, selective inner hair cell loss had a significant effect on gap detection ability across a wide range of presentation levels. These results suggest that gap detection tasks are more sensitive to inner hair cell pathology than audiometric thresholds.