Monkeys were able to move their paralyzed limbs through a direct link between the neurons and the muscle

Researchers at the University of Washington sent messages directly from single neurons in the brain to the paralyzed arm muscles of monkeys, showing that the monkeys were able to move the muscles through training

Every week, on Shabbat evening, we hear the fateful number on the radio: the number of people who died in car accidents that weekend. But with all the sorrow and pain for the victims of the road wars, we sometimes forget that the situation of the injured who survive the road accidents is not easy either. Many of them suffer for a long time from the injuries they suffered, especially if it is injuries to the nerves and spinal cord. If a person's spinal cord is severed, it is almost certain that they will remain paralyzed for the rest of their lives.

Medical and biomedical engineering researchers have been trying for many years to find a way to restore the mobility of people who have been paralyzed, without success. Last October finally marked the beginning of a solution for spinal cord injuries, when researchers at the University of Washington demonstrated a technology that allowed a monkey to move the muscles of its paralyzed hands using transmitters from the brain.

The researchers connected electrodes to the 'motor cortex' of the monkeys - an area of ​​the brain that controls voluntary movements. The electrodes monitored the neurons that were activated in that area, and the monkeys were trained in front of a computer screen that was connected to the electrodes. Each activation of neurons was recorded as an electrical signal by a computer, which translated the signal into the movement of a cursor on the screen. Through a target shooting game, the monkeys were able to reach a level of accuracy where they could only activate single neurons in their brains.

After the monkeys demonstrated that they were able to control the cursor on the screen, their arm muscles were anesthetized with a local anesthetic that blocked the passage of signals through the nerves. The monkeys were placed in front of the computer screen again, but this time the researchers converted the brain activity into electrical stimulation that was sent to the paralyzed arm muscles. The monkeys continued to play the target shooting game, but this time the movements of the cursor on the screen were accompanied by actual movements of the arm muscles, which indicated that the monkeys had regained the ability to control the paralyzed muscles. A most impressive finding was that the monkeys were able to control the contracted arm muscle and the extensor muscle, and not just one muscle.

Part of the innovation in the research stems from the discovery that each cell in the 'motor cortex' area is able to stimulate the arm muscles into activity, regardless of its previous function or the muscles to which it was linked. Previous computer-brain interfaces were designed to match only certain nerves and muscles connected to them, but the current discovery shows that the brain has the greatest flexibility of operation, expanding the development possibilities of computer-brain interfaces.

"There is no obligation for the cells to have a prior role in movement," says Eberhard A. Petz, professor of physiology and biophysics at the University of Washington in Seattle and one of the authors of the study. "We can create a direct connection between the cell and the source of movement, in which the user can learn to control and perfect it over time."

Petz and his colleagues found that the monkeys were able to improve their control over the neural activity, which accompanies the stimulation of the arm muscles, through training. Although the training time was limited by the duration of the neural blockade, the researchers found that the monkeys were able to hit the target three times more often after training. Petz predicts that in the future it will be possible to extend the training time by using implanted circuits that will create permanent artificial links between the muscles and neurons in the brain.

The discovery foreshadows a bright future for the medicine of spinal injuries, since the media and the researchers will be able to create a link between the 'motor cortex' and other sites, they will be able to bypass the damage to the spinal cord and allow the victims to move their limbs. But despite the bright hope, clinical applications in humans are still a long way off. Petz agrees that clinical applications will not arrive in the next decade, and adds that better methods must be found to record the activity of the individual neurons and to control several muscles at the same time, side by side with the design of implanted circuits that are reliable and safe to use.

In twenty years, will disabled people be able to abandon their wheelchairs and use their legs again? No one knows for sure the answer to this question, but the promising experiments show that there is no problem too big for the human brain - even if a connection to electrodes is needed.

According to the researchers of the National Health Institute