The possible role of nystagmus in motion sickness: a hypothesis.

An alternative hypothesis to that provided by conflict theory is formulated to account for motion sickness. The new approach is predicted on the oculocardiac reflex (i.e., bradycardia produced by extra-ocular muscle traction) (18) and empirical evidence that retrobulbar anesthesia significantly lowers the incidence of emesis after strabismus surgery (14). Eye muscle traction is presumed to elicit afferent signals that ultimately stimulate the vagus nerve (15). The same neuromotor sequence is presumed to occur during reflexive eye movements under vestibular control and during more complicated combinations of reflexive and voluntary eye movements. It is proposed that the blocking of afferent signals from extra-ocular muscle in an otherwise intact vestibulo-ocular system will eliminate the signs and symptoms of motion sickness normally produced in a provocative environment.