Simultaneous measurement of electrocochleography and ear canal pressure in normal-hearing adults

Abstract

The auditory system is regulated by various adaptive mechanisms that modify sound as it passes upstream to the cortex. Studying these adaptive mechanisms, such as the middle ear muscle (MEM) reflex and the medial olivocochlear (MOC) reflex, reveals how the normal auditory system adjusts to challenging listening tasks and how abnormal reflexes may contribute to perceptual difficulties experienced by patients with sensorineural hearing loss. Studies in laboratory animals reveal that MOC and MEM reflexes result in neural antimasking at the output of the auditory nerve. Antimasking effects at the level of the middle ear and at the level of the cochlear hair cells should carry over to effects observed at the output of the auditory nerve. Antimasking due to MEM and MOC reflexes has been difficult to study in humans since measurement approaches are limited to non-invasive techniques with only a single output variable (e.g., ear canal pressure). In these studies, we assess MEM and MOC function by simultaneous measurements of ear canal pressure and electrocochleography, including the cochlear microphonic potential and compound action potential. Simultaneous measurements are expected to reveal the antimasking effects of MEM and MOC reflexes to middle ear, hair cell, and auditory nerve responses.