We happen to be reading a paper that goes into phantom limbs (and other phenomena) from a cognitive science perspective in class today, if anyone is interested in reading it. It’s a short one (my favorite kind…) Google cache of Blakemore et al. (2002)
The theoretical skinny: we have an internal model of our body related to the world. We have in mind a desired outcome (a prediction), and a comparison of the desire and the actual outcome is made (this paper doesn’t go into it, but there are experiments that show we actually use a Bayesian or otherwise internal statistical model…not well proven but interesting). If our prediction was correct, e.g., our body did what we expected it to, then we do not have access to or knowledge of the comparison and won’t be aware of it happening. The box 1 experiment is an interesting example of motor control working properly with no awareness of it. An object is moved during a saccade (during which awareness of visual input is “turned off” [so you are not `aware’ of it but you are attending to it in this case]) yet you correctly point to it in the new position before you become aware of it 200ms later.
Interesting properties of phantom limbs: if you were paralyzed before the limb was removed, then normally you will experience your limb as still being paralyzed. E.g., you think it’s there but you can’t move it. And vice versa, but you lose the ability to feel as if you were moving it over time. The explanation is that knowledge of the state of the limb is not based soley on efferent data coming from the limb, but also your internal representation, or expectation, of the state of the limb. You lose the ability over time because your internal comparison realizes the discrepency and modifies the forward connections to compensate. E.g., you no longer unconsciously predict movement. This decay in activity reasonably takes time, as the neural representations have never experienced such catastrophic failure.
To me, this would suggest it would be possible that psychophysical treatments could speed up the treatment of neuropathic pain (in phantom limb cases) by making it clear to your motor system, in an implicit sense, that the limb is no longer there…but that depends on this framework.