Locomotion and motion sickness during horizontally and vertically reversed vision.

Locomotion and motion sickness during reversed vision were studied in ten normal subjects and a patient with bilateral labyrinthine loss. Whereas horizontal reversal produced moderate to severe gait disturbances as well as motion sickness in all normal subjects, vertical reversal failed to induce such symptoms. The patient, being free of motion sickness during both reversals, could not walk straight during horizontal reversal. The difference in the strength of sensory mismatch between both directions seemed to result from a difference in the role of vision for spatial orientation which is produced by the proprioceptive as well as otolithic inputs of gravity.