Effects of the Medial Olivocochlear Reflex on Cochlear Mechanics:. Experimental and Modeling Studies of Dpoae

Time-dependent changes (or adaptation) in level of distortion product otoacoustic emission (DPOAE) are partly effects of ipsilateral reflex of the medial olivocochlear (MOC) system [1]. This paper presents experimental data of DPOAE in cats and modeling results. This study addresses the following questions. How does the MOC reflex change DPOAE? Why is large adaptation of DPOAE associated with a trough of a DPOAE input/output (I/O) function? Why does DPOAE level either increase or decrease with time depending upon the stimulus condition? We hypothesize that the fast component of DPOAE adaptation is produced by a shift in the operating point of the I/O nonlinearity (Boltzmann function) of the outer hair cell (OHC), which in turn is produced by the MOC reflex through changes in the mean potential and length of the OHC and a rotation of the OHC hair bundle. The ability of the model to reproduce salient behaviors of DPOAE supports the hypothesis.