The ocular tilt reaction--a brainstem oculomotor routine.

Electrical stimulation of brainstem tegmentum in alert macaques elicits a stereotyped ocular movement routine characterized by vertical divergence and conjugate cycloversion. The movement pattern is similar to those seen in the clinical syndromes of see-saw nystagmus and skew deviation. The stimulated movement pattern is not dependent on initial eye position and cannot be produced when the animal is under barbiturate anesthesia. It is not overridden by saccadic inhibition stimulation and is present in cerebellectomized and labyrinthectomized monkeys.