Neural Pathways for Vertical Saccades: From the Superior Colliculus to Trochlear Motoneurons

Abstract

The pathways from the superior colliculus (SC) to vertical ocular motoneurons were analyzed in anesthetized cats using intracellular recording from trochlear motoneurons. Electrical stimulation of the ipsilateral or contralateral SC evoked disynaptic excitation and inhibition in trochlear motoneurons. Stimulation of the ipsilateral Forel's field H (FFH) and the contralateral interstitial nucleus of Cajal (INC) evoked monosynaptic excitation and inhibition in trochlear motoneurons, respectively. Preconditioning stimulation of the SC facilitated FFH-evoked monosynaptic excitation. The results showed that trochlear motoneurons receive disynaptic excitation via the FFH from the ipsilateral SC and disynaptic inhibition via the INC from the contralateral SC.

KEYWORDS:

• Saccade
• superior colliculus
• trochlear motoneuron
• vertical eye movement
• interstitial nucleus of Cajal