Sound-evoked olivocochlear activation in unanesthetized mice

Abstract

Genetic tools available for the mouse make it a powerful model to study the modulation of cochlear function by descending control systems. Suppression of distortion product otoacoustic emission (DPOAE) amplitude by contralateral acoustic stimulation (CAS) provides a robust tool for noninvasively monitoring the strength of descending modulation, yet investigations in mice have been performed infrequently and only under anesthesia, a condition likely to reduce olivocochlear activation. Here, we characterize the contralateral olivocochlear reflex in the alert, unanesthetized mouse. Head-fixed mice were restrained between two closed acoustic systems, while an artifact rejection protocol minimized contamination from self-generated sounds and movements. In mice anesthetized with pentobarbital, ketamine or urethane, CAS at 80 dB SPL evoked, on average, a