People with paralyzing spinal cord injuries can walk again with the help of medical devices that zap their nerves with electricity. But the designers of these new implants weren’t quite sure how to restore motor function over time — now, a new study offers clues.
The new study, which was conducted on humans and lab mice, is published November 9 in the journal Neurology nature (Opens in a new tab), identifies a specific group of neurons that appear to be key to restoring the ability to walk after a paralyzed spinal cord injury. With an electric shock, the implant can turn on these neurons and thus trigger a chain of events in which they are structured Nervous system the changes. This cellular model restores lost lines of communication between brain and the muscles The researchers concluded that it is necessary for walking, allowing people who have been paralyzed again to walk.
Understanding how a system of nerve impulses, called epidural electrical stimulation (EES), “reshapes spinal circuits can help researchers develop targeted techniques to restore gait, and possibly enable recovery of more complex movements,” Great faith (Opens in a new tab)a principal investigator at the Salk Institute for Biological Studies in La Jolla, California, and W Ki wui huang free download mp3 (Opens in a new tab)a postdoctoral fellow at Azim Lab, wrote in A Suspension (Opens in a new tab).
Nine people with paralyzing spinal cord injuries took part in the new study. Six of them were mostly or entirely unable to move their legs but retained some feeling in the extremities; The other three participants had no motor control or sensation from the waist down.
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The nine participants underwent surgery to implant electrodes over the lower spinal cord, below muscle and bone but outside the membrane that envelops the nervous system. Then each participant trained with the implant for five months. They started by practicing standing, walking, and performing various exercises indoors in weight-bearing belts, and eventually graduated to training outdoors with a stability walker.
These exercises were completed with the EES implant turned on, but in time, four of the nine participants could bear weight and walk with the device turned off, the researchers wrote in their report.
The team also found that as each participant regained their ability to walk, the general activity of their spinal cords decreased in response to EES — what initially seemed like a roaring fire of activating neurons diminished to the point of burning. This suggests that the combination of rehabilitation and electrical stimulation reorganizes the nervous system, so that fewer and fewer cells are needed to complete the same procedure.
“When you think about it, it shouldn’t come as a surprise because in the brain, when you learn a task, that’s exactly what you see — there are fewer and fewer neurons active.” The better you get, co-author Gregoire Courtine (Opens in a new tab)a neuroscientist and professor at the Swiss Federal Institute of Technology, Lausanne (EPFL), Tell nature (Opens in a new tab).
The team used rodent-sized EES implants to study how this realignment process appears mice With paralysis of the spinal cord. The mice completed the rehabilitation course, similar to the human participants, and all the while, the researchers tracked which of their neurons responded to the treatment by changing which genes they turned on.
This analysis revealed a group of neurons in the lumbar spinal cord that consistently responded to treatment, even when other neurons became less active. Blocking the activity of these neurons in uninjured mice did not affect their ability to walk, but in paralyzed mice, silencing the cells prevented them from walking again. Curtin said this suggests that while other neurons may play their own role in healing, this particular group is particularly important. Sciences (Opens in a new tab).
The findings are consistent with the idea that certain types of spinal neurons[s] Those who have lost input from the brain after injury can be “reawakened” or redirected to regain movement if they are given the right combination of stimulation and rehabilitation.” They said the trials could lay the groundwork for new and improved devices aimed at repairing the spinal cord after injury.
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