Experienced and un-experienced extensions of body parts

A well documented syndrome is that of phantom limbs, in which sensations from an amputated limb do not disappear but remain and are often painful. Subjects with this syndrome may also feel that they are able to move their limbs. In short, a missing part is not necessarily experienced as missing, even when the subject knows that it is missing.

I presume that someone born with one limb missing will not experience that limb. From which it follows that the phenomenon is due to the persistence in the brain of some record of that limb, even in its absence.

There is a counterpart to this condition, which I experience on a regular basis in the streets and the Underground system of London. People carrying backpacks or bags do not seem to be aware of the extension of their bodies, and hence are quite happy to invade my peri-personal space. They do not do so with their actual bodies, but with the artificial extensions to their bodies. They brush against me continually, sometimes forcefully, without even being aware of having done so.

Thus the brain does not appear to accommodate, in its calculation of the space occupied by the body to which it belongs, any artificial extensions of that body, even when such artificial extensions become daily props.

Presumably, if the artificial extension becomes a permanent fixture, the brain may gradually take account of it. But this must be a very long process, assuming that it occurs at all.

The result is of course most irritating, because people around us invade our peri-personal space continually, brushing against us with the artificial extensions to their bodies. A Japanese colleague of mine told me that this kind of peri-personal space invasion is much frowned upon and disliked in Japan. Good for the Japanese.

This irritating invasion of other peoples’ space by artificial extensions to the body, if appropriately studied, may give us useful hints about how the brain represents the body of which it is a part.