Lying down on the hospital stretcher with the sheets covering his body till the neck, Harry came into his consciousness. On opening his eyes wide open, he found himself surrounded by people; doctors, nurses, friends and relatives. The doctor, in a husky tenor, said,
"Sorry Harry, we could not save your arm. We had no choice but to amputate it !"
Harry was literally appalled. He spoke out in a rather outraged tone,
"What are your saying doctor! Nuisance! I don't believe it. I can still feel my arm!"
This continued until the doctor removed the sheet from his upper body and to Harry's dismay, yes, the arm was amputated. But he still vividly felt the presence of his arm.
Rather queer, isn't it ?
It seems strange to most of us who have not gone through this experience but this is true. People with an amputated arm can wobble their fingers and reach out for things in the arm's proximity in an effort to hold them tight.
On coming across such experiences, we will characterize such people as crazy or psychotic since according to us this is not possible in reality.
No.
This is genuine. These patients feel the presence of a phantom in their amputated arm because the fact that they still have their arm attached to their body, still crawls and runs into their brain. The patients often receive sensations from their arms and sometimes they feel as if they can successfully use their limbs in gesticulation during a speech. Some patients feel grievous pain from this phantom limb although they are completely aware of the fact that their arm does not exist.
It is believed that the brain takes considerable time, which we are uncertain of, to adapt itself to the fact that the arm no longer exists and hence the sensations which are felt by the patients are due to the reviewing of the wide sensory information that the brain has. Also, it should be taken into consideration that the nerve ending of the amputated arm in the neuromas become provoked and ignited and hence the higher thinking centers of the brain are under the illusion that the arm still exists. The irritated neuromas send signals to the brain and hence the brain is fooled.Although the balderdash tales of the people are infinite. Many draw the analogy of this incident from what happens when someone passes away and one tends to see the souls of the deceased in the dreams. Also in one of the cases, it was found that when a man felt sensations in his amputated arm, he wanted to know what actually happened to the detached part of his arm. So on doctor's advice, he went to the morgue where he came to know that the arm was not cremated. It was funny but the arm had been sent to the pathology lab, which is generally not the case. In the lab, he was informed that due to an abundance of arms, the arm was buried and hence when the arm was checked it had worms crawling over it. As soon as the arm was  burnt the sensations, apparently caused by the worms, was no longer felt. But this is simply unscientific and there would be many who would not want to go along with this reason and hence would prefer the one given earlier.
One must take into consideration the mapping of sensations on the entire body surface onto the surface of the brain. Hence, when Ramachandran used this to investigate these sensations by experimenting on a man, blindfolded, he came across the fact that when specific areas of face and arms were touched, the sensations in the fingers were felt. The person felt as if his fingers were touched when the cheeks or other portions of the arms were stroked. This was because, on the sensory cortex of the brain, where the sensations or touch signals have been mapped, the sensations on the face and sensations on the arms are mapped below and above the position where fingers are mapped on the brain. Ramachandran used Tim Pon's paper where monkeys with paralyzed arm were used to observe the change in their brain circuitry after eleven years. But the limitation was that monkeys couldn't speak and therefore Ramachandran thought of doing this on humans because he wanted to know if the sensations were felt on the face as well as on the amputated or paralyzed in the case of monkeys) arm, or the higher thinking centers of the brain interpreted it as sensations from the face only.