The mammalian cochlea receives innervation from the central nervous system
via two efferent systems: the lateral and the medial olivocochlear bundles.
Advances in cochlear physiology have clarified the origins and termination
s of these fibers. However, to date, while the functional significance of l
ateral efferents remains totally unknown, that of medial efferents is still
controversial. The peripheral effects of medial olivocochlear system activ
ation have been described, but the role of this inhibitory feedback onto th
e cochlea is still unclear. This overview summarizes the main results of se
veral psychophysiological studies performed in humans dealing with the func
tional significance of medial olivocochlear efferents in hearing.