From the WashU Newsroom…
Temporarily shutting off neuronal signals to a healthy part of the brain may aid stroke recovery, according to new research in mice.
The findings, from researchers at Washington University School of Medicine in St. Louis, are published Jan. 31 in Science Translational Medicine.
Mice that had experienced strokes were more likely to recover the ability to use a front paw if their whiskers were clipped following a stroke. Trimming the whiskers deprives an area of the mouse’s brain from receiving sensory signals from the animals’ whiskers. And it leaves that area of the brain more plastic – or receptive to rewiring to take on new tasks.
“We may have to rethink how we do stroke rehabilitation,” said senior author Jin-Moo Lee, MD, PhD, the Norman J. Stupp Professor of Neurology at the School of Medicine. “Stroke rehab often focuses on trying to train patients to compensate for disability caused by the stroke, but this strategy has limited effectiveness. Our findings suggest that we may be able to stimulate recovery by temporarily vacating some brain real estate and making that region of the brain more plastic. One way to do that might be by immobilizing a healthy limb.”
About 450,000 people survive strokes every year. Because the brain is adaptable, people typically recover a limited amount of function naturally. For example, a person who is unable to move his arm the day after a stroke sometimes can wiggle his fingers a week later. Brain imaging on such people shows that control of the fingers shifts from the stroke-damaged area of the brain to a neighboring undamaged area, a process known as remapping. How thoroughly a person recovers correlates with how well his or her brain rewires and moves functions from injured to uninjured areas.
But this adaptability also means there’s a constant battle for control over the brain’s real estate. Normally, if neuronal signaling to one area gets cut off – by sensory deprivation or limb amputation, say – neighboring functions will spread into that unused area.
Lee, first author Andrew Kraft, an MD/PhD student at Washington University, and colleagues reasoned that shutting off signals to an uninjured area near the site of stroke damage would promote remapping into that area by generating vacant real estate.
The researchers triggered, in mice, a stroke in the part of the brain that controls the right forepaw. Then, they trimmed whiskers in half of the mice to induce sensory deprivation in a brain region near the stroke and left the whiskers of the other mice intact. Mice rely on their whiskers, which are rich with nerve endings, to sense the location of objects in their environment.
The researchers measured recovery by comparing right and left forepaw use. Immediately after the strokes, both groups of mice favored their left forepaws. But by four weeks after the strokes, those with clipped whiskers had begun using their right forepaws again, and by eight weeks, they were back to using both equally. In contrast, mice whose whiskers were not clipped showed no improvement at four weeks and only partial recovery at eight weeks.
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