Melbourne: How a phantom limb forms depends on how the nerves are stimulated during amputation or injury, a new study has claimed.

A person is said to have a "phantom limb" when he or she continues to perceive sensations in limb even when the body part is no longer there, such as after amputation.

Now, a team at Neuroscience Research Australia has found that there is no default position that the phantom moves into after it forms.

"Our research suggests that the state of nerves in the limb at the time the phantom is forming is very important in determining how the phantom develops," said team leader Prof Simon Gandevia.

Because distortions of body image, such as phantom limbs, are difficult to treat, a better understanding of the mechanisms behind their formation will help developing more effective treatments.

Prof Gandevia and colleagues conducted an experiment in which they temporarily anaesthetised participants' hands to induce a phantom limb.

The team found that the state of the nerves – i.e, how much they were being stimulated -- over the period when participants were losing sensation in their hand was a key in determining the final perceived position of the phantom hand.

"This might also be true for phantom pain. In other words, the amount and type of nerve stimulation around the time of amputation or injury could also be important in determining the type and degree of pain perceived in the phantom limb," Prof Gandevia said.

The findings have been published in 'The Journal of Physiology'.

(Agencies)