A comparison of the efferent effects of the homolateral and contralateral olivo-cochlear bundles

Both efferent olivo-cochlear bundles, contralateral (COCB) and homolateral (HOCB), were stimulated in cats under the same conditions. Stimulation was carried out either in the nuclei of origin or along the course of the bundles. The same results were obtained in both series of experiments. Both bundles cause action potential (AP) depression with the COCB having an effect about 6 times stronger. The AP depression of both is greatest during low frequency, low intensity acoustic stimulation. In contrast to COCB stimulation, no change in the cochlear microphonic potential or latent period was observed with HOCB stimulation. The significance of these results is discussed and it is suggested that the contralateral and homolateral efferent systems to the cochlea act independently of each other.