EFFERENT SYSTEM, CENTRAL MASKING AND PERC EPTION IN NOISE

In order to investigate the role of the auditory efferents in percepti on, controlateral suppression of evoked otoacoustic emissions (EOAEs) was examined together with 1) central masking and 2) detection in nois e in normal hearing subjects. The first study, concerning the relation s between the contralateral suppression of EOAEs and central masking a t 1 kHz, put into evidence the existence of a significant negative cor relation between the amount of central masking obtained with a delay o f 20 ms between the test and the mask and the modifications of the amp litude of EOAEs induced around 1 kHz by a contralateral 30 dBSL broadb and noise stimulation. In the second study, a correlation was found be tween the mean equivalent attenuation of EOAEs and the variation of th e tone-in-noise detection threshold, both induced by a contralateral 3 0 DBSL broadband noise stimulation. These results support the hypothes is that the crossed part of the medial olivo-cochlear system is actual ly involved in auditory perception in humans.