Influence of vision on vibration-induced illusions of limb movement.

Illusory motion of the unseen stationary forearm can be elicited by vibration of the biceps brachii or triceps brachii muscle. We have studied in 12 individuals how sight of part of the arm alone or in relation to other objects affects such vibration-induced, illusory motion of the forearm. Our findings indicate a complex but systematic influence of vision in attenuating apparent motion of the forearm. They show, too, that the seen and felt positions of the forearm can be dissociated and that physically impossible spatial configurations of the arm can be experienced. These findings have implications for physiological theories of position sense.