Schematic model of corticofugal effects on ABR waves.

Red arrows represent descending pathways of the auditory efferent network. Orange arrows represent afferent connections of the ascending auditory pathways. From the obtained results, we propose that corticofugal effects on SOC (wave III) and auditory nerve (wave I) are driven through medial olivocochlear synapses on OHC. On the other hand, corticofugal effects on IC responses are mainly produced through direct connections (i), however indirect effects through MOC-OHC synapses, and then through ascending connections (ii) are also possible. IC: inferior colliculus; MGB: medial geniculate body; SOC: superior olivary complex; CN: cochlear nucleus.