Responses of vestibular and prepositus neurons to head movements during voluntary suppression of the vestibuloocular reflex.

Neurons in the vestibular nuclei and the prepositus nucleus exhibited several different types of changes in their firing behavior during voluntary cancellation of the horizontal VOR. The head velocity sensitivity of type I position-vestibular-pause neurons was reduced during cancellation, while type II vestibular neurons exhibit an increase in their sensitivity. The firing behavior of burst tonic neurons in the medial vestibular nucleus, the prepositus nucleus, like the cells in the abducens nucleus, was closely related to the eye movements generated when the VOR is cancelled. Other cells in the PH and MVN respond primarily to smooth pursuit eye movements. We suggest that the behavior of abducens neurons during the VOR and during VOR cancellation can be explained if they receive inputs from PVP neurons, burst tonic neurons, and smooth pursuit neurons.