Brains Retain Complex Information About Missing Limbs Decades After Amputation

New research opens doors to advanced prosthetic design.

Scientists have discovered that a brain holds onto information related to a missing limb decades after its amputation, regardless if the person experiences ‘phantom limb’ syndrome. 

SEE ALSO: Virtual Reality Program Helps Prosthetic Limbs Feel Connected to Amputees' Bodies

Scientists looked at the brains of people who were born with a missing limb compared to those that suffered an amputation; the amputees' brains had detailed information related to their missing limbs.

The research could assist scientist working on the next generation of prosthetics that tap into the brain's own neural networks for control.

The study follows on from the team's previous research where they examined the brains of two people who had lost their left hand through amputation between two and three decades ago.

MRI scan shows complex information retention

Using powerful MRI’s the scientists saw that although diminished the brain activity that makes up the composition of the hand picture in the brain were well matched to those of two-handed people. 

"Our previous findings demonstrated the stability of the hand picture in the cortex despite decades of amputation," explains lead author Daan Wesselink, a Ph.D. student at the University of Oxford and UCL Institute of Cognitive Neuroscience, UK. 

"However, we didn't know whether this hand representation in the brain reflects phantom sensations and therefore only persists in those few people who experience vivid sensations."

To understand what role the phantom limb syndrome influenced the study the researchers examined 18 amputees that lost their limb on average 18 years ago. The group had varying phantom limb sensations. The researchers compared their brain decoding analysis of this group with 13 people who were born with a hand missing from birth.

People born with missing limbs have less limb information

Both groups were asked to ‘move’ their missing and intact hands while inside an MRI scanner. The results showed that the brains of the people in the group who had lost limbs from amputation retained the strongest information about their missing limb, even those that have fewer sensations also have the same brain activity. This is fascinating because those people have no knowledge on a daily basis that their brain has retained any information about their missing limb.

The group who were born without a limb, show some neural imprint of a hand but at a significantly reduced rate. This shows that building next-generation prosthetics will still be a challenge for those born without limbs.

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"We've shown that once the hand 'picture' in the brain is formed, it is generally unlikely to change, despite years of amputation and irrespective of the vividness of phantom sensations," concludes senior author Tamar Makin, Associate Professor and Sir Henry Dale Fellow at the UCL Institute of Cognitive Neuroscience.

"Our work suggests that daily life experience could shape the fine-grained aspects of hand representation, but that the large-scale functional organization of the hand area is fundamentally stable," he continues.

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