Time course of the medial olivocochlear efferent effect on otoacoustic emissions in humans

The time course of the medial olivocochlear efferent system has been studie d in humans, using the suppressive effect of a contralateral broad-band noi se (CBBN) on 2f1-f2 distortion product otoacoustic emissions (DPOAE) amplit ude. DPOAE were recorded with F2 at 1.5 kHz, with a temporal resolution of 2.6 s, in the presence and absence of a 40 dB SL continuous CBBN, whose dur ation ranged between 30 s and 20 min. The CBBN suppressive effect on DPOAE amplitude was greatest from the first 2.6 s, and was sustained for 20 min. At the CBBN offset, when the CBBN duration was greater than or equal to 2 m in, DPOAE amplitude continued to increase for > 1 min, showing an efferent effect outlasting CBBN stimulation. NeuroReport 9: 3741-3744 (C) 1998 Lippi ncott Williams & Wilkins.