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With willpower, and a jolt of electricity, paralyzed rats learn towalk again [video] by ferujkll sdff
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With willpower, and a jolt of electricity, paralyzed rats learn towalk again [video] by FERUJKLL SDFF
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| Article Posted: 02/26/2013 |
| Article Views: 108 |
| Articles Written: 2023 - MORE ARTICLES FROM THIS AUTHOR |
| Word Count: 1141 |
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With willpower, and a jolt of electricity, paralyzed rats learn towalk again [video] |
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The rat stood on its hind limbs at one end of a narrow runway. Itwore a tiny black vest attached to a robotic arm that hovered aboveits head. Without such mechanical support, the rat would havefallen over—its spinal cord had two deep cuts, rendering itsback legs useless. Rubia van den Brand , then a doctoral candidate at the University of Zurich, stood atthe other end of the runway, urging the animal to walk. Althoughthe robotic arm kept the rat upright, it could not help thecreature move; if the rodent were ever to walk again, it would haveto will its feet forward.
For the first time since van den Brandbegan her experiments, the rat moved one of its back legs on itsown—a small, effortful step. She ran to her boss's officewith the news and a crowd immediately gathered in the lab to watchwhat many had deemed impossible. Van den Brand and Grégoire Courtine , now at the École Polytechnique Fédérale deLausanne (E.P.F.L.), along with their colleagues, have trained ratswith nearly severed spinal cords to walk again . One week after being injured, the rats could not move their hindlimbs at all.
Six weeks later they could walk, run, climb stairsand even sprint—but only with the support of the robotic armaccompanied by electrical and chemical stimulation of the spinalcord. Rats that trained on a moving treadmill instead of on astationary runway moved their feet reflexively but never learned towalk voluntarily. Only conscious participation in walkingencouraged new connections between the rodents' brains, spinalcords and limbs, which they needed to take those first deliberatesteps. "It's kind of like how a toddler learns to walk,"Courtine says.
"Their spinal cord is full of activity and thebrain needs to learn to take control of the spinal cord. As long asthe brain has something to control it can learn progressively tocommunicate again with these cells." To mimic the kind of severe spinal cord injury that paralyzes many people, the researchers anesthetized the animals and sliced deep into two spots on either side of the rats' spinalcords, severing many neural connections running from the brain downthe back, but sparing a small bridge of tissue between the lesions.As an analogy, imagine carving two notches out of opposite sides ofa thick rope, dividing many of the individual strings in thebundle, but not quite cutting the rope in half. After a week's recovery time the rats could not budge their hindlimbs—they only dragged themselves around by their frontlegs. Van den Brand and her colleagues settled on thevest-and-robotic-arm apparatus as a way to force the rats to usetheir back legs. First, however, the researchers began to wake up dormant neurons below the lesions in the rats' spinal cords—cells that hadbeen cut off from the upper spinal cord and brain.
Courtine and hiscolleagues stimulated the lower spinal cord with electrodes and acocktail of chemicals that act as neurotransmitters, moleculesneurons use to communicate with one another. With the assistance ofsuch stimulation—and the robotic arm—rats placed ontheir hind legs on a treadmill went through the motions of walking.But none of the movement was voluntary. The spinal cord canorchestrate most of the motions involved in walking without helpfrom the brain, as long as it gets sensory input from theenvironment—such as the ceaseless motion of the treadmill.Courtine and his team wanted to restore conscious, deliberatemovement to the rats. The researchers divided the rats into three groups: One grouplearned to walk on a treadmill; another learned to walk along astationary runway and a set of steps; and a third received notraining.
Rats in each of the first two groups trained for about 30minutes every day for several weeks as they received electric andchemical stimulation. All the while researchers providedencouragement, either by cheering or offering some chocolate. Twoto three weeks later, the rodents training on the runway took theirfirst voluntary steps. By six weeks the same rats had learned tosprint and walk up a small staircase. The treadmill-trained ratsnever learned to take voluntary steps.
When Courtine and his colleagues dyed the rats' spinal cords andbrains—specifically the motor cortex, a band of tissue thathelps plan and direct voluntary movement—they observedextensive new networks of neurons in rats that trained on therunway but not in those that trained on the treadmill. Anelectrophysiological test provided similar evidence. Stimulatingthe motor cortex with electrodes before the surgeries made therats' leg muscles twitch. Immediately after surgery their legs didnot move in response to the same stimulation.
But when Courtineelectrically stimulated the brains of rats that learned to walkacross the runway, their legs twitched once again, indicating thatthe active training had reestablished some of the neuralconnections between brain, spinal cord and legs. Courtine thinksthat surviving neurons may have grown new links with one another across the remaining sliver of tissue in thespinal cord, bypassing the lesions. In summary: Forcing the rats toget their brains involved in rehabilitation restored voluntarymovement of their hind limbs; removing the need for the brain'sinvolvement with a treadmill ruined any chance of regainingconscious control. The results appear in the June 1 issue of Science . "This is not a cure for spinal cord injuries," Courtinesays, "but what we are working on is quite surprising andencouraging.
It's a very different concept from what has been donebefore, clearly showing that what is really important is to promotea highly functional state during training." Reggie Edgerton of the University of California, Los Angeles, who has conductedsimilar research with both animals and people, was impressed withwhat he called "a very important study." Edgerton was part of a team that helped 25-year-old Rob Summers, who was paralyzed from thechest down after a hit-and-run accident, learn to stand, flex his limbs on command and walk on a treadmill with the help of harness and electrical stimulation of the lowerspine. In all likelihood, Summers's determination and willpowercontributed to his achievements, just as the rats in the new studyonly regained voluntary control when they were forced to activelythink about walking. "This new work helps provide some insights into what themechanisms might be for what we have previously observed inhumans," Edgerton says. "The most important informationis that you have to engage the brain and make the brain try toregain function.
Even if a connection does not yet exist, you canstill consciously try. You've got to activate the circuits so theycan figure out how to get to the lower spinal cord. This group hasput a lot of pieces together from earlier research—we'rebeginning to get a better understanding of some new possibilities.It's a new ball game for rehabilitation. We now know there issignificant plasticity even years after injury.". I am a professional writer from Bag & Luggage Making Materials, which contains a great deal of information about rat live traps , nursery rhyme bedding, welcome to visit!
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