Functional asymmetries of crossed and uncrossed medial olivocochlear efferent pathways in humans.

In a previous study, a peripheral auditory asymmetry in right-handers was found. The activity of the uncrossed medial olivocochlear efferent pathway has been shown to be more effective in the right than in the left ear. Our aim was to compare right and left medial olivocochlear inhibition during contralateral, ipsilateral and binaural ear stimulation with a broad band noise, in order to better localize this asymmetry. Uncrossed pathway asymmetry was confirmed and the crossed pathway showed a reverse asymmetry: a left ear advantage. These results are in accordance with the assumption that the medial superior olivary complex is the locus of the asymmetry observed. As this nuclear complex receives central efferents, the peripheral auditory asymmetry may be related to the well-known cortical asymmetry.