Topographical representation of vestibulo-ocular reflexes in rabbit cerebellar flocculus.

In anaesthetized albino rabbits, the cerebellar flocculus was systematically mapped with a glass microelectrode to identify the location of Purkinje cells that inhibit specific vestibulo-ocular reflex pathways. The effects of microstimulation of the flocculus Purkinje cell layer on vestibular nerve-evoked reflexes to ipsilateral medial rectus, ipsilateral superior rectus and contralateral inferior oblique muscles were explored by recording electromyographically. Visual climbing fibre inputs to the flocculus were also studied by mapping field potentials evoked from both retinae. The results suggest that there are microzones in the flocculus that are related specifically to these three vestibulo-ocular reflex pathways and to different visual climbing fibre pathways.