Rather than simply replacing the head, the team attached the donor head to the body of the larger rat, creating an animal with two heads.

Scientists say they have carried out a successful head transplant on rats ahead of plans to attempt a similar operation on a human later this year.

During the procedure, the head of a smaller rat was attached to the body of a larger rodent.

Rather than simply replacing the head, the team attached the donor head to the body of the larger rat, creating an animal with two heads.

The operation involved three rats in total: the donor, the recipient and a third used to maintain the blood supply to the transplanted head.

A pump was used to transfer blood from the third rat to the donor head to ensure the brain was not starved of oxygen.

After the procedure, the rat whose head had been transplanted was able to see and feel pain, showing the brain was functioning despite having been detached from its original body.

The experiment, reported in the journal 'CNS Neuroscience and Therapeutics', was designed to investigate issues relating to blood flow to the brain and the possibility of the immune system rejecting the new organ - problems that could arise during a human transplant.

The procedure was carried out by a team including Sergio Canavero, a controversial Italian neurosurgeon who has pledged to carry out a human head transplant this year.

Hunt Batjer, president elect of the American Association for Neurological Surgeons, has criticised Mr Canavero's plans to transplant a human head.

Irish Independent