Without visual reference to the horizon, the motion of the ship is perceived by the vestibular and proprioceptive systems while the bulkheads do not appear to move relative to the observer. One theory postulates that the sensory conflict described above stimulates a response in the brain stem similar to that caused by some neurotoxins. This mechanism evolved to rid the body of toxic ingested substances by emptying the stomach, and countering or minimizing the effects of absorbed toxin via a stress response of the sympathetic nervous system. In individuals and animals in whom the vestibular apparatus has been ablated or the vestibular pathway interrupted, motion sickness has not been induced, despite extensive effort. However, a differential diagnosis should be considered in cases of persistent illness or illness refractory to management.
Most individuals adapt to a motion environment over a period of time that varies in length.
Personnel should be advised to minimize their exposure to motion by residing amidships or over the wing in airplanes, and to limit their own head movements to prevent confusing vestibular input. Additionally, maintaining a visual reference to the horizon should be helpful. Alcohol intake in the previous 24 hours has been shown to reduce tolerance to cross-coupled stimulation during desensitization training. Thus, limiting alcohol intake may reduce susceptibility. Medications include parasympathomimetics, antihistamines, often used in combination with stimulants.