Walsh & Hoyt: Pathogenesis of Saccadic Intrusions

The brainstem circuits responsible for generating saccades are well worked out and provide a means for testing brainstem and cerebellar function. Thus, the saccadic command is generated by burst neurons of the brainstem reticular formation that project monosynaptically to ocular motoneurons The burst neurons for horizontal saccades are located in the PPRF, whereas the burst neurons for vertical and torsional saccades are located in the riMLF. Burst neurons discharge only during saccadic eye movements. The activity of all saccadic burst neurons is gated by omnipause neurons, which are crucial for suppressing unwanted saccades during fixation and slow eye movements. The omnipause neurons are located in the caudal pons within the raphe interpositus nucleus (RIP), adjacent to the abducens nucleus. Inputs into omnipause neurons arise in the superior colliculus, frontal eye fields, and mesencephalic reticular formation.