Differential effects of noise trauma and diminished endocochlear potential on neural temporal coding of complex sounds: Implications for speech perception

Abstract

Communication problems due to cochlear hearing loss are pervasive in today’s society, even with amplification from digital hearing aids. Threshold elevation may arise from noise-induced trauma to hair cells or, as an alternative mechanism, through age-related depletion of the endocochlear potential (EP; the power supply driving hair-cell function). While both noise trauma and diminished EP may frequently underlie hearing loss in older people, it is unclear whether these pathologies have different effects on neural coding of complex sounds, and ultimately, on speech perception. Here, we describe several recent neurophysiological studies of this question based on Wiener-kernel analyses of chinchilla auditory-nerve fiber responses to Gaussian noise. We find that noise trauma causes pronounced distortions in tonotopic coding of temporal fine structure and slower envelope cues, occurring with as little as 20 dB threshold elevation. Similar changes in neural coding occur with diminished EP, but only when thresh...