Change in susceptibility to vestibular-visual conflict sickness in monkeys by repeated exposure.

Squirrel monkeys, susceptible to the vestibular-visual conflict sickness in pitch (with frank vomiting), were subjected to repeated exposure to pitch conflict in various modes and in a randomly mixed order (30 min daily, for 10 consecutive days). Immediately after the training, a significant decline in susceptibility was found, represented by reduced vomiting rates, reduced sickness scores, reduced salivation and improved regularity of vertical oculomotor responses. Susceptibility at the pre-training level returned when the test was repeated 10 days later. Temporary suppression of pitch conflict sickness susceptibility indicates the possibility of training crew members prior to their space flight missions to control the space motion sickness, particularly vomiting.