ACOUSTIC ENHANCEMENT OF ELECTRICALLY-EVOKED OTOACOUSTIC EMISSIONS REFLECTS BASILAR-MEMBRANE TUNING - EXPERIMENT RESULTS

Acoustic enhancement of the electrically-evoked otoacoustic emissions (EEOEs) was investigated by systematically varying acoustic frequency and intensity. The results demonstrated that simultaneous acoustic sti mulation at frequencies around the characteristic frequency of the ele ctrical current injection place was most effective in enhancing low-fr equency EEOEs. Moreover, it was demonstrated that the enhancement was tuned and graded. The enhancement threshold tuning curves (defined as sound pressure level needed to achieve 1 dB of enhancement) resembled basilar membrane tuning at high sound pressure levels. The data sugges t that the emissions were generated from a cochlear region near the el ectrode place, and the magnitude of the enhancement depends on the mag nitude of the basilar membrane response to the acoustic stimulus.