Sensory conflict. Vestibular, visual, and proprioceptive afferents provide complementary information about the motion and position of the body in space. Normally this information is congruent—it matches. In type A conflicts, visual and vestibular afferents contradict each other. In type B conflicts, signals from the semicircular canals and otolith organs of the vestibular apparatus are incongruent or ambiguous. Unless the inputs from multiple sensory organs can be integrated, the information they provide remains incomplete. On its own, the visual system cannot reliably distinguish between motion of the body and motion of the environment (e.g., perception of vection [self motion] experienced by an observer in a stationary train when another train pulls in alongside). The semicircular canals register angular acceleration of the head, but their signal decays over the course of a long, smooth turn. The otolith organs register the size and direction of linear acceleration, including that of gravity (g↓). Because the same direction of acceleration can result from (a) an inclination of the head or (b) a combination of horizontal and vertical accelerations, the signals from the otolith organs need to be supplemented by the other afferents. | Bertolini G, Straumann D: Moving in a moving world: A review on vestibular motion sickness. Front Neurol 2016; 7: 14.

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