Mind exercise maps for the hand (proven in crimson) and lips (blue) earlier than the amputation (Pre1 and Pre2) and after amputation (three, six and 18 months post-amputation). Credit score: Tamar Makin / Hunter Schone
The mind holds a “map” of the physique that continues to be unchanged even after a limb has been amputated, opposite to the prevailing view that it rearranges itself to compensate for the loss, in keeping with new analysis from scientists within the UK and US.
The findings, revealed in Nature Neuroscience, have implications for the therapy of “phantom limb” ache, but additionally recommend that controlling robotic substitute limbs through neural interfaces could also be extra simple than beforehand thought.
Research have beforehand proven that inside an space of the mind often known as the somatosensory cortex there exists a map of the physique, with completely different areas similar to completely different physique components.
These maps are answerable for processing sensory data, comparable to contact, temperature and ache, in addition to physique place. For instance, if you happen to contact one thing scorching together with your hand, it will activate a specific area of the mind; if you happen to stub your toe, a distinct area prompts.
For many years now, the commonly-accepted view amongst neuroscientists has been that following amputation of a limb, neighboring areas rearrange and basically take over the realm beforehand assigned to the now lacking limb. This has relied on proof from research carried out after amputation, with out evaluating exercise within the mind maps beforehand.
However this has offered a conundrum. Most amputees report phantom sensations, a sense that the limb continues to be in place—this will additionally result in sensations comparable to itching or ache within the lacking limb. Additionally, mind imaging research the place amputees have been requested to ‘transfer’ their lacking fingers have proven mind patterns resembling these of able-bodied people.
To analyze this contradiction, a workforce led by Professor Tamar Makin from the College of Cambridge and Dr. Hunter Schone from the College of Pittsburgh adopted three people on account of bear amputation of considered one of their arms.
That is the primary time a examine has seemed on the hand and face maps of people each earlier than and after amputation. A lot of the work was carried out whereas Professor Makin and Dr. Schone have been at UCL.
Previous to amputation, all three people have been capable of transfer all 5 digits of their arms. Whereas mendacity in a practical magnetic resonance imaging (fMRI) scanner—which measures exercise within the mind—the individuals have been requested to maneuver their particular person fingers and to purse their lips. The researchers used the mind scans to assemble maps of the hand and lips for every particular person. In these maps, the lips sit close to to the hand.
The individuals repeated the exercise three months and once more six months after amputation, this time requested to purse their lips and to think about transferring particular person fingers. One participant was scanned once more 18 months after amputation and a second participant 5 years after amputation.
The researchers examined the alerts from the pre-amputation finger maps and in contrast them towards the maps post-amputation. Evaluation of the ‘earlier than’ and ‘after’ photographs revealed a exceptional consistency: even with their hand now lacking, the corresponding mind area activated in an virtually equivalent method.
Professor Makin, from the Medical Analysis Council Cognition and Mind Science Unit on the College of Cambridge, the examine’s senior writer, mentioned, “Due to our earlier work, we suspected that the mind maps could be largely unchanged, however the extent to which the map of the lacking limb remained intact was jaw-dropping.
“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.”
As earlier research had urged that the physique map reorganizes such that neighboring areas take over, the researchers seemed on the area similar to the lips to see if it had moved or unfold. They discovered that it remained unchanged and had not taken over the area representing the lacking hand.
The examine’s first writer, Dr. Schone from the Division of Bodily Drugs and Rehabilitation, College of Pittsburgh, mentioned, “We didn’t see any signs of the reorganization that is supposed to happen according to the classical way of thinking. The brain maps remained static and unchanged.”
To enhance their findings, the researchers in contrast their case research with 26 individuals who had their higher limbs amputated, on common, 23.5 years beforehand. These people confirmed related mind representations of the hand and lips to these of their three case research, suggesting long-term proof for the steadiness of hand and lip representations regardless of amputation.
The researchers supply an evidence for the earlier misunderstanding of what occurs throughout the mind following amputation. They are saying that the boundaries throughout the mind maps are usually not clear reduce—whereas the mind does have a map of the physique, every a part of the map does not help one physique half solely.
So, whereas inputs from the center finger could largely activate one area, in addition they present some exercise within the area representing the forefinger, for instance.
Earlier research that argue for enormous reorganization decided the structure of the maps by making use of a “winner takes all” technique—stimulating the remaining physique components and noting which space of the mind reveals essentially the most exercise; as a result of the lacking limb is now not there to be stimulated, exercise from neighboring limbs has been misinterpreted as taking on.
The findings have implications for the therapy of phantom limb ache, a phenomenon that may plague amputees. Present approaches deal with attempting to revive illustration of the limb within the mind’s map, however randomized managed trials to check this strategy have proven restricted success—immediately’s examine suggests it is because these approaches are centered on the incorrect drawback.
Dr. Schone mentioned, “The remaining components of the nerves—nonetheless contained in the residual limb—are now not linked to their end-targets. They’re dramatically reduce off from the sensory receptors which have delivered them constant alerts. With out an end-target, the nerves can proceed to develop to type a thickening of the nerve tissue and ship noisy alerts again to the mind.
“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.”
Of the three individuals, one had substantial limb ache previous to amputation however obtained a fancy process to graft the nerves to new muscle or pores and skin; she now not experiences ache. The opposite two individuals, nevertheless, obtained the usual therapy and proceed to expertise phantom limb ache.
The College of Pittsburgh is considered one of a variety of establishments that’s researching whether or not motion and sensation might be restored to paralyzed limbs or whether or not amputated limbs is perhaps changed by synthetic, robotic limbs managed by a mind interface. This examine means that as a result of the mind maps are preserved, it ought to—in principle—be attainable to revive motion to a paralyzed limb or for the mind to manage a prosthetic.
Dr. Chris Baker from the Laboratory of Mind & Cognition, Nationwide Institutes of Psychological Well being, mentioned, “If the brain rewired itself after amputation, these technologies would fail. If the area that had been responsible for controlling your hand was now responsible for your face, these implants just wouldn’t work. Our findings provide a real opportunity to develop these technologies now.”
Dr. Schone added, “Now that we have proven these maps are steady, brain-computer interface applied sciences can function beneath the idea that the physique map stays constant over time.
“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. This study is a powerful reminder that even after limb loss, the brain holds onto the body, waiting for us to reconnect.”
Extra data:
Schone, HR et al. Secure Cortical Physique Maps Earlier than and After Arm Amputation, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-02037-7
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Gone however not forgotten: New analysis reveals the mind’s map of the physique stays unchanged after amputation (2025, August 21)
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