USE OF DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS TO ASSESS MIDDLE-EAR TRANSDUCERS IN RHESUS-MONKEYS

Distortion product otoacoustic emissions (DPOAEs) can provide an objec tive and noninvasive assessment of the peripheral cochlear function, A uditory brainstem responses measured from implanted rhesus monkeys hav e shown that middle ear transducers, coupled directly to the incus, ar e capable of delivering the signals to the central auditory system. Th e DPOAEs were used as a noninvasive method of assessing the frequency specificity of this mechanical transduction. In two rhesus monkeys imp lanted with the middle ear transducers, one primary stimulating tone ( f1) was presented acoustically, and the other primary tone (f2) was pr esented by the transducer, which converted the signal into a mechanica l motion of the probe tip attached to the body of the incus. The nonli near characteristics of the cochlea produced the distortion product re sponses at the expected frequencies (2f1 - f2). This demonstrates the fidelity of the middle ear implant signal transduction in vivo. The DP OAEs also indicate minimal changes in the post-implant middle ear tran smission. This study demonstrates that the DPOAEs can be used to asses s the function of implanted middle ear transducers objectively and non invasively.