Abstract
Lesions of the interstitial nucleus of Cajal (INC) in cats and monkeys result in severe impairment of the vestibulo-ocular reflex (VOR) in the pitch plane and vertical optokinetic reflex, and impairment of the ability to hold an eccentric vertical eye position after saccadic movement. The INC region of alert animals contains many burst-tonic and tonic neurons whose activity is closely correlated to vertical eye movement, not only during spontaneous saccades, but also during pitch VOR, smooth pursuit, and optokinetic eye movements. Although this activity is closely related to these conjugate vertical eye movements, it is different from oculomotor motoneuron activity. Because the INC region alone cannot produce eye-position signals, the INC is an essential component but not sole component of the velocity-to-position integrator for vertical eye movement.
The INC and closely surrounding midbrain reticular formation contain a class of cells that have properties required for vertical burster-driving neurons. Chemical deactivation of these areas produces selective impairment of generation of vertical fast eye movement. These results indicate that the INC and nearby reticular formation may also be involved in generating vertical fast eye movements.
