Vision-Driven Kinesthetic Illusion in Mirror Visual Feedback.

In the paradigm of mirror visual feedback, it remains unclear how images of the mirrored hand directly affect the sense of motion of the hidden hand (kinesthetic illusion). To examine this question, we created an original mirror visual feedback setup using a horizontal mechanism of motion for the mirror and the hidden hand, each of which could independently be given a specific velocity. It should be noted that this setup can cause the hand viewed in the mirror to move without the involvement of the visible hand. In the experiment, the participants reported the felt direction of the hidden hand's displacement (left/right) after 4 s dual movements with quasi-randomized velocities. It was found that the subjective direction of motion of the hidden hand was strongly biased toward the direction of the mirror. Further, anatomical congruency was found to affect kinesthetic illusion for cases where the mirror approaches the visible hand.