The areas of the brain responsible for recognizing our hands can also recognize a prosthetic limb in the same way — particularly if it’s used regularly.

Photo courtesy of The Johns Hopkins University Applied Physics Laboratory (JHU/APL).

Prosthetics have progressed tremendously in recent years, with some bionic prosthetics being controlled by thought alone. But this progress has also raised additional questions, especially in terms of how the brain deals with all of this. Now, for the first time, a study has shown how the brain ‘sees’ prosthetics, and it’s encouraging news.

“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,” said the study’s lead author, Dr Tamar Makin from the UCL Institute of Cognitive Neuroscience.

“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 study included 32 people with one hand — half of whom were born this way, and another half which had lost a hand through amputation — and 24 people with both hands who served as the control group (most of them were friends or family of the one-hand group).

All participants were shown photos of prostheses, as well as real limbs, and a fMRI machine was used to gauge their neural response to the images — particularly the visual cortex.

Within the visual cortex, there is a brain area which ‘lights up’ when people recognize hands. People with one hand displayed a much stronger response, particularly those who used a prosthesis regularly. In other words, they saw a the prosthetics much as real limbs. Interestingly, this carried out even for prostheses that are functional but do not look like a hand, such as a hook prosthesis.

The area of the brain responsible for controlling the hand also lit up for prosthesis users of both groups — the brain was attempting to control the missing hand.

If you think about it, it makes a lot of sense. Even though people understand that the prosthesis is not the real hand, they use it the same way, so it’s normal for the brain to treat it similarly too.

“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.

“To me this is natural, having one hand is how it’s always been. The prosthesis is part of me, I don’t regard it as an addition – I consider it a hand,” said another study participant, John Miller, who was born with only one hand and regularly uses his prosthesis.

The study was published in the journal Brain.