Different roles of flocculus and ventral paraflocculus for oculomotor control in the primate.

Responses of Purkinje cells were compared in the monkey flocculus and ventral paraflocculus. During vestibuloocular reflex (VOR) eye movements, flocculus Purkinje cells exhibited simple spike modulation related to head velocity, while ventral paraflocculus Purkinje cells exhibited modulation with no such head velocity preference. During smooth tracking of a sinusoidally moving small target, ventral paraflocculus Purkinje cells exhibited simple spike modulation related to target velocity or position, while the flocculus Purkinje cells exhibited a smaller modulation with no such target preference. Visual suppression of the VOR enhanced the simple spike responses in the ventral paraflocculus, but not in the flocculus. These results suggest that the primate flocculus and the ventral paraflocculus control differentially VOR and smooth pursuit eye movements, respectively.