Cerebellar actions on cochlear microphonics and on auditory nerve action potential

The influence exerted by cerebellar stimulation upon cochlear microphonics (CM) and auditory nerve action potential (AP) has been analyzed in curarized guinea pigs. Round window recordings demonstrated that conditioning electrical stimulus trains delivered to the cerebellar cortex diminished the CM and AP amplitude at the same time and in a parallel fashion. On the other hand, cooling of the cerebellar cortex showed the opposite results of increased amplitudes. All pre-receptorial mechanisms were avoided. A PDP-12 computer performed parametric and non-parametric statistical analysis showing the differences to be significant for the shifts. Evidence of simultaneous inhibitory cerebellar action on both potentials has been demonstrated and a cerebello-olivo-cochlear pathway is proposed for such action upon the receptor cells and/or incoming fibers.