A new study has found the brain holds a ‘map’ of the body that remains unchanged after amputation.
The study challenges previous assumptions about amputation and provides hope that technologies which use neural interfaces to control prosthetic limbs can be developed. The authors also suggest the findings will help guide treatment of phantom limb pain.
“If the brain rewired itself after amputation, these technologies would fail,” says Dr Chris Baker from the Laboratory of Brain & Cognition at the US National Institute of Mental Health.
“Our findings provide a real opportunity to develop these technologies now.”
Brain activity maps for the hand (shown in red) and lips (blue) before the amputation and 3, 6 and 18 months post-amputation. Credit: Schone et al., Nature Neuroscience, 2025
Previous studies have uncovered there is a ‘map’ of the body within the somatosensory cortex region of the brain. In this map, certain regions of the cortex correspond to parts of the body and limbs. These maps help the brain process sensory information like pain and touch.
Neuroscientists have previously thought that after an amputation of a limb, the regions of the brain responsible for mapping the amputated limb get reorganised and repurposed to other parts of the body.
But this understanding does not account for people who report phantom sensations, such as feeling as though the limb is still in place, or itchy or painful sensation. Approximately, 60 to 70% of amputees experience phantom limb pain in the year after amputation.
So, the team of scientists from the UK’s University of Cambridge and the University of Pittsburgh in the US investigated this conundrum by analysing the brain maps of 3 individuals before and after they underwent an amputation.
This is the first time a study has looked at brain maps both before and after an amputation.
Participants involved in the study were able to move all 5 fingers before the amputation. In the first part of the study, the participants were asked to move their fingers while they were lying in a functional magnetic resonance imaging (fMRI) scanner.
The participants repeated this scan 3 and 6 months after their amputation. This time they were asked to imagine moving their individual fingers.
When the researchers examined the pre- and post amputation brain scans, they noticed the same corresponding brain region was consistently activate.
“This study is a powerful reminder that even after limb loss, the brain holds onto the body, waiting to reconnect,” says lead author Dr Hunter Schone from Pitt Rehab Neural Engineering Labs.
“We didn’t see any signs of the reorganisation that is supposed to happen according to the classical way of thinking. The brain maps remained static and unchanged.”
The researchers compared their results to 26 participants who had upper limbs amputated about 20 years ago. These participants had similar brain activity to the first group.
“Because of our previous work, we suspected that the brain maps would be largely unchanged, but the extent to which the map of the missing limb remained intact was jaw-dropping,” says Tamar Makin, professor of cognitive neuroscience at Cambridge.
“Bearing in mind that the somatosensory cortex is responsible for interpreting what’s going on within the body, it seems astonishing that it doesn’t seem to know that the hand is no longer there.”
New interventions currently being developed rely on robotic sensors and controllers to move prosthetic limbs using algorithms.
The researchers suggest that if these brain maps are preserved, it could be the key to potentially allowing the brain to control a prosthetic limb.
“Now that we’ve shown these maps are stable, brain-computer interface technologies can operate under the assumption that the body map remains consistent over time,” says Schone.
“This allows us to move into the next frontier: accessing finer details of the hand map, like distinguishing the tip of the finger from the base, and restoring the rich, qualitative aspects of sensation, such as texture, shape and temperature.”
“The most promising therapies involve rethinking how the amputation surgery is actually performed, for instance grafting the nerves into a new muscle or skin, so they have a new home to attach to,” says Schone.
The results from this study have been published in Nature Neuroscience.