The corticofugal (descending) auditory system forms multiple feedback loops, and adjusts and improves auditory signal processing in the subcortical auditory nuclei. However, the mechanism by which the corticofugal system modulates cochlear hair cells has been unexplored. We found that electric stimulation of cortical neurons via the corticofugal system modulates cochlear hair cells in a highly specific way according to the relationship in terms of best frequency between cortical neurons and hair cells. Such frequency-specific effects can be explained by selective corticofugal modulation of individual olivocochlear efferent fibers.