Article in Aeon-How the body and mind talk to one another to understand the world--Sarah Garfinkel

[rvallee]

Since Jonathan didn't have a go, I will try.

Phantom limb phenomena relates to the fact that the mind (as a result of development of a young organism) builds up a model of the limb and this is used as a comparative basis for proprioception (including effort perception) in general. This is one of the proposed functions of the supplementary motor area (and related areas) for example. Effort perception of movement is primarily based on the signals in the brain and not peripheral signals, though peripheral signals in turn can still feed back into that model over time so the model remains somewhat accurate as our bodies change.

When a limb is severed, the nerves are severed, but the model in the brain remains and as the ends of the nerves try to regenerate, they can become sensitive to signals that they aren't supposed to be sensitive to, hence pain being a problem in some cases.

Our sense of position can also be modified with visual input, which is why the mirror can help, though I speculate that the benefits are overstated.

I personally favor a theory of mind that makes prediction the core of how intelligence works, that predicting the future is the essential characteristic of intelligence. The brain constantly predicts things and adjusts its future predictions based on differences from those predictions. That's how we develop the ability to do things mindlessly, like walking without thinking about it because our brains predict the proper sequence and will alert to any significant change from what was predicted.

Our brains predict that following a sequence of movement, it will meet resistance from the ground and when that doesn't happen (like a hole in the ground) it triggers the executive to react and draw attention to a marked difference from what was expected.

Then having built a cognitive map of having a limb, the brain continues to make predictions about what that limb should be doing, where it should be based on proprioception and what sensations it should be getting from that limb (as the lack of sensation is a big deal) and that triggers the executive to bring attention to the fact that there is no limb where one should be and that is a big freaking deal as it's definitely supposed to be there.

It's been years since I've had the ability to read developing work but that was always the theory of mind that made the most sense to me and how we can properly define intelligence. Some mind that could predict the future with great accuracy always rank very high in people's perception of what superior intelligence is, something false prophets have long used to their advantage.

 

[Jonathan Edwards]

I agree that predictive coding is an essential part of sensations of touch and movement. I am not sure it plays the same role for pain, though. I don't know the answer to this but my guess is that people with phantom limb pain do not have a very clear idea what position the non-limb is in, just that it is painful. That is what you get if you wake up having slept on your arm, with a numb painful hand that you cannot tell the position of.

The predictive coding model goes along with the assumption that the brain is always working with differentials or changes in inputs. If you stare at a picture with no saccades for two minutes the image will evaporate. My suspicion is that for a non-limb there will be no differentials going on the the stumps of the interoceptive nerves much and the predictive side will pretty much shut down. But that's a guess.

As a caveat to that, I suspect that pain is dependent on predictions from other sensory inputs to a degree. The sensory inputs we have on the soles of our feet when we stand might well be called pains if they occurred at night when we were lying flat with nothing on our feet.

I would pretty much agree with the what Snow Leopard put but i do agree that it may be complicated.