Visualizing motions within the cochlea's organ of Corti and illuminating cochlear mechanics with optical coherence tomography

•OCT can detect motions of cells and structures within the sensory tissue of the cochlea.•Structures within the sensory tissue move differently than the basilar membrane.•OHCs show active motion to frequencies well below the best frequency.•Perturbations related to deafness modify motions within the sensory tissue.•Motion within the sensory tissue is related to otoacoustic emissions. Beginning in 2006, optical coherence tomography (OCT) has been adapted for use as a vibrometer for hearing research. The application of OCT in this field, particularly for studying cochlear mechanics, represents a revolutionary advance over previous technologies. OCT provides detailed evidence of the motions of components within the organ of Corti, extending beyond the first-encountered surface of observation. By imaging through the bony capsule as well as through the round window membrane, OCT has measured vibration at multiple locations along the cochlear spiral, in vivo, under nearly natural conditions. In this document, we present examples of recent research findings to illustrate the applications of OCT in studying cochlear mechanics in both normal and impaired ears.