Abstract
Ramachandran, Altschuler and others have shown that the mirror reflection of a moving intact limb can cause phantom sensations in nonamputees, and reduce phantom limb pain in single-limb amputees. Peterzell and colleagues report that these effects sometimes are increased using multiple mirrors (“out-of-body” reflections) or stroboscopic self-motion (“the phantom pulse”) (VSS 2006, 2007). Two new mirror-symmetry effects are reported here.
(1) Ramachandran's mirror technique was used on two amputees, albeit with amputations below BOTH knees. The mirror was positioned to reflect the left side of each amputee's body as he sat in a folding chair viewing the mirror. I (the experimenter) positioned my left leg underneath the chair, facing the mirror. As I moved my left ankle and toes slowly and predictably, the amputee watched the reflection and imagined that he was seeing and moving his missing right ankle and toes. While viewing the mirror for 10 minutes, both individuals reported a sense of (a) movement in the right phantom ankle and toes, (b) a growing or “telescoping” of the shrunken, retracted phantom limb to normal size, and (c) a temporary reduction of stress and pain in the phantom right ankle, foot and toes.
(2) Non-amputees faced a computer screen, viewing realtime images of themselves with either the left or right half flipped to create a mirror-symmetric face and torso. When observers placed the visible hand's palm at the midline (creating the illusion of two hands in prayer), some subjects felt warmth or tingling in the visible palm and fingers. In responsive individuals, similar effects were obtained by the illusory touching of fingers, forearms, and feet; “touching” one's tongue to its mirror image caused a sense of mild electric shock.
Results may suggest ways to optimize pain treatments, and further elucidate visual processes underlying phantom sensations.