Study Shows The Brain’s Body Map Remains Stable After Limb Loss

New investigation from nan University of Pittsburgh School of Medicine and Cambridge University upends a long-standing belief astir encephalon plasticity.

A study published coming successful Nature Neuroscience shows that nan brain's built-in "body map" remains unchangeable moreover erstwhile nan assemblage undergoes drastic changes, specified arsenic nan nonaccomplishment of a limb.

The findings person implications for nan curen of "phantom limb" symptom and propose that achieving reliable restoration of sensation and controlling robotic replacement limbs via brain-computer interfaces whitethorn beryllium much viable successful nan agelong word than antecedently thought.

This study is simply a powerful reminder that moreover aft limb loss, nan encephalon holds onto nan body, waiting to reconnect."

Hunter Schone, Ph.D., lead author, postdoctoral investigation chap astatine Pitt Rehab Neural Engineering Labs

Foundational neuroscience investigation has shown that nan somatosensory cortex – an area of nan encephalon located conscionable down nan frontal lobe – holds a rich | and analyzable representation of nan body, pinch different regions corresponding to different assemblage parts. The region corresponding to nan manus and fingers, for example, lays adjacent to nan area representing lips, chemoreceptor and eyes.

These maps are responsible for processing sensory information, specified arsenic touch, somesthesia and pain, arsenic good arsenic assemblage position. For example, rubbing thing basking pinch nan manus activates a encephalon region conscionable supra nan ear.

For decades, neuroscientists thought that losing a limb caused nan brain's assemblage representation to reorganize. Neighboring regions would invade and repurpose nan encephalon area that antecedently represented nan now amputated limb, nan aged reasoning went. But this mentation has agelong conflicted pinch diligent experiences arsenic galore group proceed to consciousness vivid sensations of their missing limbs. Adding to nan puzzle, erstwhile encephalon imaging studies person shown that erstwhile individuals who person had an amputation effort to move their phantom limbs, their encephalon activation patterns intimately lucifer those of able-bodied individuals.

To analyse this contradiction, a squad led by Tamar Makin, Ph.D., professor of cognitive neuroscience astatine nan University of Cambridge, followed 3 individuals owed to acquisition amputation of 1 of their hands – nan first clip a study has looked astatine nan manus and look maps of individuals some earlier and aft amputation. Most of nan activity was carried retired while Makin and Schone were astatine University College London.

Researchers asked study participants to move, aliases effort moving, their fingers and purse their lips while lying successful a magnetic resonance imaging (MRI) scanner. These functional MRI scans were taken anterior to nan planned manus amputation and past again 3 and six months aft surgery. One subordinate was scanned again 18 months aft amputation and a 2nd subordinate 5 years aft amputation.

Analysis of nan 'before' and 'after' images revealed singular consistency: moreover pinch their manus now missing, nan corresponding encephalon region activated successful an almost identical manner.

"Because of our erstwhile work, we suspected that nan encephalon maps would beryllium mostly unchanged, but nan grade to which nan representation of nan missing limb remained intact was jaw-dropping," Makin said. "Bearing successful mind that nan somatosensory cortex is responsible for interpreting what's going connected wrong nan body, it seems astonishing that it doesn't look to cognize that nan manus is nary longer there."

Researchers besides confirmed that nan region corresponding to nan lips had not taken complete nan region representing nan missing hand, disproving long-held assumptions that nan assemblage representation tin drastically reorganize.

The researchers deliberation that nan misconception comes from methodology flaws. While nan encephalon does person a representation of nan body, each portion of nan representation doesn't support 1 assemblage portion exclusively – which is why activity from neighboring areas connected nan representation could beryllium misinterpreted arsenic taking over.

Study findings besides explicate why curen approaches focusing connected restoring practice of nan limb successful nan brain's representation person shown constricted occurrence for phantom limb symptom – possibly they tackled nan incorrect problem. The astir promising therapies impact rethinking really nan amputation room is performed, scientists say.

Reconnecting remaining parts of nan nerves wrong nan residual limb to caller musculus aliases tegument could extremity nan nerves from sending signals that lend to nan emotion of symptom backmost to nan brain. Anecdotally, of nan 3 participants, each of whom had important limb symptom anterior to amputation, 1 received a analyzable process to graft nan nerves to caller muscle. That subordinate is now pain-free.

Not only does nan study situation a long-held belief astir brain plasticity, but it besides suggests that restoring activity aliases sensation to a paralyzed limb aliases a prosthetic controlled by brain-computer interface – nan benignant of activity spearheaded by researchers astatine Pitt Rehab Neural Engineering Labs -- is imaginable successful nan long-term.

"Now that we've shown these maps are stable, brain-computer interface technologies tin run nether nan presumption that nan assemblage representation remains accordant complete time," said Schone. "This allows america to move into nan adjacent frontier: accessing finer specifications of nan manus map, for illustration distinguishing nan extremity of nan digit from nan base, and restoring nan rich, qualitative aspects of sensation, specified arsenic texture, style and temperature."

Chris Baker, Ph.D., of nan Laboratory of Brain & Cognition, National Institutes of Mental Health, and others contributed to this research.