In the video we wached in class about neurologist Ramachadran, one of the disorders we learned about was the phantom limb. The phantom limb is when someone who has had a body part amputated (whether it be an arm, leg, fingers etc), continues to feel the presence of that missing limb. This can occur immediately after having the limb amputated or several years later. The amputee might even feel pains on his "phantom limb", or other sensations. If they were wearing a ring, or watch, they might even still feel the presence of that jewelry as well.
In one case, a patient whose lelft arm had been amputated felt as if his amputated hand was making a fist, but because he no longer had his arm he could not unclench it. Ramachandran created a mirror box, in which the patient could put his exitsting hand and trick the brain into thinking the reflection was his amputated hand. When he unclenched his right hand, he was able to relieve the clenching sensation that he was eperiencing.
I found an article explaining another set of experiments regarding the phantom limb theory. This article discusses Ramachandran's discoveries on how the phantom limb can also be present in normal individuals who have had no amputations. Even though phantom limbs are regarded as pathological, they were able to generate the same illusion in normal individuals.
In their phantom nose experiment, (Ramachandran and Hirstein 1997), a person was blindfolded and instructed to tap his own nose with his left hand. They then placed a second person in front of him so that they were facing each other, and had him tap this person's nose with his right hand, while he continued to tap his own nose with his left hand. After several seconds, the person blindfolded begins to feel as though their nose is either in two places or has been dislocated. This is because without seeing, the brain assumed both hands are touching the same nose.
It's fascinating how easily the brain can be tricked when not all five senses are being used. Even just by taking away our sense of vision, a normal, sane person can be tricked into thinking his nose has been dislocated or even extended.