RELATIONSHIP BETWEEN AUDITORY INTENSITY DISCRIMINATION IN NOISE AND OLIVOCOCHLEAR EFFERENT SYSTEM ACTIVITY IN HUMANS

Recent physiological data in animals suggest a role of tie medial oliv ocochlear system (MOCS) in auditory intensity discrimination in noise. In this study, the existence of statistical relationships between int ensity difference limens (IDLs) and MOCS functioning was tested in hum ans. IDLs were measured in conditions of quiet and of ipsilateral, con tralateral, and dichotic noise. MOCS functioning was assessed through the contralateral evoked otoacoustic emission (EOAE) amplitude attenua tion effect. A first finding was that IDLs measured in the presence of ipsilateral noise were,:educed when contralateral noise was added. Fu rthermore, the observed shift in IDL appeared to be significantly corr elated to the contralateral EOAE amplitude attenuation effect. These r esults support the hypothesis that MOCS functioning plays a role in in tensity discrimination in dichotic noise in humans.