A new study has revealed how artificial limbs are represented in the brains of amputees.
Neural network
The study, led by University College London, included 32 people with one hand, alongside 24 people with two hands who were used as a control group. Both groups were shown images of prosthetic hands, including their own prostheses, as well as real limbs. An MRI scan was then used to assess the neural responses of the participants.
The brain has an area within the visual cortex that enables people to recognise hands. The researchers found that the participants with a prosthetic hand had a stronger neural response compared to the control group, particularly among those who used a prosthesis frequently in their daily lives. This part of the brain also responded to images of prostheses that are functional but do not look like a hand.
The researchers also investigated the connectivity between the visual hand-selective area and the area of the sensorimotor cortex which would be expected to control the missing hand. They found that there was better connectivity between these two brain areas for people who used their prostheses regularly.
Clare Norton, a study participant who has had one hand amputated, said: “Logically I know my prosthesis is not my missing hand – it's a tool, it's a new sensation and I accepted that. The more I use my prosthesis, the more I feel like it becomes a part of me,” said Clare Norton, a study participant who has had one hand amputated.”
The study’s lead author, Dr Tamar Makin, said: “While the use of a prosthesis can be very beneficial to people with one hand, most people with one hand prefer not to use one regularly, so understanding how they can be more user-friendly could be very valuable.”
“If we can convince a person’s brain that the artificial limb is the person’s real limb, we could make prostheses more comfortable and easier to use.”
The researchers state that their findings could be used to guide rehabilitation strategies as well as prosthesis design. There is potential for the study to guide other types of augmentation technology as well.
The study’s first author, Fiona van den Heiligenberg, said: “Our findings suggest that the key determinant of whether the brain responds similarly to a prosthetic hand as it does to a real hand, is prosthetic use. As many of our study participants lost their hand in adulthood, we find that our brains can adapt at any age, which goes against common theories that brain plasticity depends on development early in life.”
