I first heard about phantom limbs in a journal club some three years ago. I don’t know any amputees or people who have lost their limbs, so when I heard that a very large percentage of amputees experienced “phantom limbs” I was more than surprised. If a limb is amputated, it is gone, finis. But apparently many amputees can still feel their amputated limb moving. What is more, this is accompanied often by excruciating pain which they cannot control. Even more bizarre is the Capgras delusion, which is something practically taken out of Bollywood movies, except it is imaginary. Here, the person with Capgras delusion absolutely believes that some acquaintance (a friend or family member, say) has been replaced by an identical looking impostor. To the delusional patient, the impostor looks the same, sounds the same, feels the same, but is an impostor!
V. Ramachandran, at the center for brain and cognition at UCSD is one of the pioneer researchers of these phenomena. Almost more importantly, he is an engaging, eloquent and charismatic speaker. Not long ago, he gave a talk at TED, which is more than well worth your time.
Take 20 minutes off whatever you are doing, and enjoy the talk. (If the video doesn't work from the browser, you can view and download it here).