Narrow elliptical motion at the outer hair cell-Deiters’ cell junction explains disparate features of uniaxial displacement measurements

Abstract

Sound-evoked displacement responses at the outer hair cell-Deiters’ cell junction (OHC-DC) are of significant interest in cochlear mechanics, as OHCs are believed to be in part responsible for active tuning enhancement and amplification. Motion in the cochlea is three-dimensional, and the architecture of the organ of Corti complex (OCC) suggests the presence and mechanical importance of all three components of motion. Optical coherence tomography (OCT) displacement measurements of OHC-DC motion from different experimental preparations often show disparate results, potentially due to OCT measuring only the motion component along the beam axis. In this work, we show that narrow elliptical motion at the OHC-DC – nearly along a straight line, where towards-base longitudinal motion is in phase with towards-scala-media transverse motion – can explain two such preparation-dependent differences. We present longitudinal and transverse components of displacement responses from the OHC-DC in the gerbil base in response to moderately high-level sound stimuli that exhibit precisely this near-lineal motion. The results show the potential for active longitudinal energy transfer in the OCC.