Results of a new study are challenging the long-held belief that the human brain significantly changes itself following the loss of a limb — and this new information could help clinicians to better support patients before and after amputation.
The study — Stable cortical body maps before and after arm amputation — was published Aug. 21 in Nature Neuroscience.
Researchers used longitudinal neuroimaging for three adults whose progress was tracked before and up to five years after arm amputation.
“We compared cortical activity elicited by movement of the hand (before amputation) versus phantom hand (after amputation) and lips (before and after amputation),” the study said. “We observed stable cortical representations of both hand and lips in primary sensorimotor regions. By directly quantifying activity changes across amputation, we demonstrate that amputation does not trigger large-scale cortical reorganization.”
The study said that although previous research — involving monkeys and human subjects — suggested that amputating an arm “triggers large-scale cortical reorganization of the S1 body map, with a dramatic redistribution of cortical resources, hijacking the deprived territory,” this latest study suggested something different.
Tamar Makin, Ph.D., professor of cognitive neuroscience at the University of Cambridge and the study’s team leader, said in a University of Pittsburgh announcement, “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. 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.”
Hunter Schone, Ph.D., a postdoctoral associate at the University of Pittsburgh and lead author of the study, said this new research “is a powerful reminder that even after limb loss, the brain holds onto the body, waiting to reconnect.”
Those findings could help researchers to develop better treatments for phantom limb pain — described by the National Institutes of Health as “the perception of pain or discomfort in a limb that is no longer there” — and to support changes in how amputation surgeries are performed.
The University of Pittsburgh news announcement said, as an example, that one of the three study participants “received a complex procedure to graft the nerves to new muscle. That participant is now pain free.”
The university also said the study “suggests that restoring movement or sensation to a paralyzed limb or a prosthetic controlled by brain-computer interface — the kind of work spearheaded by researchers at Pitt Rehab Neural Engineering Labs‚ is possible in the long term.”
