The Dynamic Neck-eye Reflex in Mammals

Stimulation of cervical proprioceptors by torsion of the neck results in movement of the eyes. The pathways of this neck-eye reflex have been identified electrophysiologically, and in individuals with vestibulo-ocular deficits the reflex is often seen to contribute to retinal image stability during head movements. In intact individuals, however, its role in ocular compensation for head movements is questionable. In this and other studies, the reflex eye movements were in the direction opposite the vestibulo-ocular reflex and were, therefore, anticompensatory. In four species of mammal (rat, rabbit, cat, and bush baby - a primate), the reflex was most consistently elicited with an anticompensatory phase; furthermore, when an animal partially stabilizes its head in space (by the vestibulo-collic reflex) during body rotation, the vestibulo-ocular and neck eye reflexes must have opposite polarities if their summation is to be of use to the animal. The neck-eye reflex appears to be absent when the animal actively moves its head; it only appears during the experimental procedure employed to elicit the reflex. An alternative function for the electrophysiologically identified pathway of the neck-eye reflex is suggested.