CONTRALATERAL SUPPRESSION OF EVOKED OTOACOUSTIC EMISSIONS AND DETECTION OF A MULTITONE COMPLEX IN NOISE

Although some findings suggest that auditory efferent fibers are invol ved in perception in noise, their function remains controversial. The contralateral suppression of evoked otoacoustic emissions (EOAEs) has recently provided a means of exploring the medial olivocochlear system (MOCS) in humans. In an experiment based on this paradigm, the presen t study examined the relationships between variations of both EOAEs an d detection-in-noise thresholds, induced in the same subjects by a con tralateral 50-dB-SPL broad-band noise masker. EOAEs were recorded in r esponse to a burst of a multitone complex composed of 1, 1.5 and 2-kHz components. The detection thresholds of this 3-component complex were measured at 2 ipsilateral noise levels: 50 and 70 dB SPL. The main fi nding was a significant correlation between EOAE suppression and thres hold variations under contralateral masking. A relationship was also f ound between the contralateral suppression of EOAEs and threshold vari ation induced by the increase in ipsilateral noise level. These findin gs support the notion that the MOCS is involved in the detection of mu lticomponent stimuli in noise.