In it I found a post, The Mirror Cure for Phantom Pain, which is linked to an article by Lorimer Moseley, PT and currently pain researcher at Oxford.
The article by Moseley, also called The Mirror Cure for Phantom Pain, has just been published in SciAm.
"To consider how mirror movements might reduce pain, it might be helpful to first consider what pain is. I argue that pain emerges from the brain in accordance with the brain's unconscious perception of danger to the body part in question. Sensory input of danger (called nociception) is important, but not sufficient (nor necessary actually), for pain. Perhaps mirror movements simply convince the brain that all is exactly as it should be, which removes the brain's need to evoke pain. Alternatively, perhaps mirror therapy is a great distracter: distraction remains our most effective analgesic. Such explanations are very reasonable, but not particularly exciting.
Here is a more exciting theory, one the authors' introduction suggests they had in mind. It is based on the idea that phantom limb pain results from an internal conflict in the brain. Although sensory feedback, from the nerves that used to supply the missing limb, tells the brain that the limb is still present, visual feedback tells the brain it is not. According to that theory, seeing the phantom would remove the conflict and attempting to move the phantom (i.e. the other two conditions) might exacerbate it (although removing visual feedback didn't help, which doesn't fit neatly into the theory). That anaesthetizing the stump can eliminate phantom limb pain seems consistent with this theory. Perhaps anaesthetizing the stump brings sensory feedback into line with visual feedback, whereas mirror movements bring visual feedback into line with sensory feedback."
He goes on to discuss implicit versus explicit movement, citing one study showing no difference, and another that does.
References, additional reading:
1. The Neurotopian: Mirror Box Therapy
2. The Neurotopian: Pain for Dummies
3. Neurotonics: blogpost search for Virtual Body
4. List of publications by Lorimer Moseley (up to 2005)