Debate: Phantom limbs

do people born whith out a limb still get the same fellings as amputis do in ther missing limbs.

I understand that the body sensory map for the face is geographically located close to that for the hand. In a new born baby these are two very important points of sensory input. Would this not explain why the newly formed brain might place these two areas very close to each other?

Actually I 'm hardly convinced that amputees don't "use" their lost limbs representations, when they re trying to make sense of other people's actions and intentions.

I just wonder how do amputees feel in situations where primary reflexes are released, such as in the case of protective reactions to balance disturbances, how do they feel under deep body pressure, and finally how do they feel when they watch the execution of a complex motor task which requires sophisticated praxis abilities. Is anyone aware of relevant findings or reports?

Peter's comment reminds me the poor effect that visual strategies may have on the remediation of dyspraxic children compared to the effects of programes triggering "hidden" senses (proprioception, vestibular & tactile). Obviously most amputees are people who have normally developed "action maps" on the basis of integration of visual & somatosensory information. If "mirror neurons" still call for the release of bilater "action plans" while peripheral information coming to the system is distorted, the senasation of a "frozen limb" seems a logical consequence. Here comes up a question then. If we are able to impact upon central somatosensory processing through manipulating visual information is there any way to replicate this impact by manipulating in any way the peripheral somatosensory info? (eg. applying deep pressure or light touch in close areas to inhibit "protective & arousing" or discriminative tactile processing respectively).

manos

I was fascinated by the idea of phantom limbs being "contactable", and the overlapping of the mapping of the body in the brain. I wondered if this is why acupuncture works?

I am a reamputee .I had my right leg taken off twice, below knee then above knee. This was in October 2000. I still get phantom pains. Anyone with an answer to my problem. Maggie

Perhaps part of the answer to the ‘retain rather than lose, although not use’ problem of the phantom limb is that, at the neuronal level, the absent limb actually continues to be used. For example, a young man had a motorcycle accident, which resulted in the loss of one arm. Subsequently it felt to him as if that hand was continually gripping the handlebars in a vice-like grip, producing a constant feeling of painful cramp. Such cases have been alleviated by getting the patient to ‘flex’ the missing limb. This has been done both in hypnosis and by means of a mirror. In the latter case the mirror is positioned so that the reflection of the preserved limb looks as if it is actually in the place of the missing limb. When the fingers of the real hand are flexed, the reflection appears to be the missing hand moving. This technique has been successful in removing the pain of a phantom limb in many cases.

In response to the 'use it or lose it ' question of why the phantom limb remains, although it can never be used, the answer, I believe, can be found in VS Ramachandran's book, 'Phantoms in the Brain, Human Nature and the Architecture of the Mind'. In the chapter, 'Knowing Where to Scratch', he describes a set of ingenious experiments based on knowledge of the homunculus, or little man in the brain.

On the surface of the cortex there lies a representation of the entire body surface. In this representation, the neurones responsible for the hand are in close proximity to those responsible for the facial image. Ramachandran then hypothesised that perhaps the neurones representing the missing arm, after receiving no input for a time, migrate into the area representing the face - a hypothesis that turned out to be true.

An easy test for this was to blindfold the patient and then gently stroke the patient's face, predictably, yet still incredibly, the patient said that he felt Ramachandran stroking his missing arm. Ramachandran's theory was therefore that, due to the migration of the nerve cells, any movement against the cheek of the patient, even a slight breeze, would trick the brain into believing that the arm was still present and still receiving messages from the surrounding environment.

Due to this neuronal reorganisation, as far as the brain is concerned, the arm is still being used, and will therefore not be lost. In fact, it takes several days for the patient to start experiencing the phantom limb phenomena, exactly the time necessary for the brain's body image to change. In the sense of 'use it or lose it', the limb is 'lost' during this period, unfortunately for some people, the mind cannot deal with such a sense of loss and tries it's best to find it again.