25 September 2014

Get up and go!

Rat Race

Alexander Telishev, "Russian Planet"

Swiss neurophysiologists and their Russian colleagues announced on Wednesday, September 24, the creation of a system of electrochemical stimulation of the spinal cord, which allows you to return full freedom of movement of the legs to rats paralyzed due to spinal rupture. Scientists plan to test this technology next summer, which allows full control of leg movements using a computer, on volunteers. The results of experiments on rodents were published in the journal Science Translational Medicine (Wenger et al., Closed-loop neuromodulation of spinal sensorimotor circuits controls refined locomotion after complete spinal cord injury).

"I want to emphasize that my team and I do not claim that we have found a way to treat paralysis. We simply collected all the necessary scientific data and tools in order to adapt the therapy that we tested on rats to restore mobility to people using our innovative technology of adapted gait. We hope that we will start clinical trials next summer," says Gregoire Curtin from the Swiss Federal Polytechnic Institute in Lausanne.

As a rule, damage to the spine as a result of car accidents, falls and other accidents leads to the fact that a person loses mobility of legs, arms or the whole body. Over the past ten years, scientists have developed more than a dozen potential ways to cure paralysis, some of which use stem cells for this purpose, while others rely on electrical stimulation of neurons or more exotic techniques. For example, in August 2014, Japanese neurophysiologists presented to the world an original technique for restoring the mobility of the legs by connecting them to the hands using a special chip.

Kurtin and his colleagues, including Russian physiologist Pavel Musienko from the Institute of Physiology of the Russian Academy of Sciences in St. Petersburg, have been trying to solve this problem for almost six years. A Swiss biologist became interested in this problem back in 2009 after noticing that isolated fragments of the spinal cord in the spines of several paralyzed rats "came to life" and began to independently control the movement of the animal's legs with electrical and chemical stimulation of their neurons.

The scheme of the experiment. Source: Swiss Federal Institute of Technology (EPFL)

These movements were not conscious, the rodents' legs began to walk only if scientists placed them on a treadmill and the animal could not control their work. Nevertheless, this fact prompted the Swiss neurophysiologist and his associates to the idea that combined electrochemical stimulation can help the paralyzed to gain freedom of movement.

In 2012, Kurtin's group made the first serious breakthrough – they managed to get rid of paralysis of rats whose spinal cord was only partially damaged. This became possible due to the fact that scientists literally deceived their wards – they created a special robot that supported the rat's body and did not let it lose its balance.

The robotic harness created the illusion that the animal's spine was in perfect order and that the rodent was independently controlling its movements. This self-deception gradually reprogrammed the intact parts of the spinal cord and forced them to transmit movement commands coming from the skull to the neurons of the legs.

In the following experiments, Curtin and his colleagues tried to go further and began to look for ways to restore connections between the two halves of the spinal cord, which were completely separated from each other. During these experiments, biologists periodically connected electrodes to an isolated fragment of the spine, studying the performance of those nerve centers that control the movement of the hind legs of rats.

"We conducted experiments with rats whose spinal cord was divided into two parts, one of which was not connected to the brain in any way, as a result of which the animal was completely paralyzed. In order to restore mobility to rodents, we used two components – a cocktail of special drugs and electrical stimulation. We have developed technologies that allow you to monitor the movement of the animal in real time and adjust the impulses entering the spinal cord. This allows the rat not only to walk, but also to climb stairs and make other complex movements," explains the Swiss biologist.

When the authors of the article completed the testing of several rats, they unexpectedly discovered that by changing the frequency and strength of electrical stimulation of the spine, it is possible to control how high the animals' legs rise and what movements they will perform. This fact prompted them to a simple and, as it turned out, extremely effective idea – they tried to copy the impulses with which the brain of healthy rodents controls the movement of the legs.

To do this, Kurtin and his colleagues began to monitor the activity of nerve cells in the spine of healthy rats and the movement of the legs, using special label stickers and a set of 14 infrared cameras. When scientists have accumulated enough information on leg movements and related impulses in nerve cells, they have developed a self-learning computer algorithm capable of controlling the work of motor neurons in an isolated area of the spinal cord of an animal.

"We have gained full control over the operation of the rat's hind legs. The rodent cannot independently control their movement, but the severed part of the spinal cord can be turned on again and make the animal walk. We can change in real time how and in which direction the rat moves forward and how high it raises its paws," explains Curtin.

This program allowed scientists not only to control the movement of the rodent in a straight line, but also gave them the opportunity to force the animal to climb stairs and perform other complex movements. Interestingly, the computer "conductor" of the legs is not inferior in the speed of its work to the rat brain – it sends a command to move to the spinal cord and corrects all errors that occur during their execution in just 20 milliseconds. This algorithm, as noted by neurophysiologists, can be used not only to turn animals into a kind of "zombie", but also to connect their brain to the damaged part of the spine or control the movement of their own legs using joysticks or other controllers.

Today, Curtin and his colleagues are working on adapting this technology, which they called ActiveGait, to restore mobility to volunteers with a partially damaged spine. They are assisted in this by the University of Lausanne Hospital, which has allocated them a separate room in which enlarged versions of a robotic "harness", a treadmill and a set of infrared cameras of a new generation will be placed. As the authors of the article hope, next summer they will be able to collect the necessary data to adapt their algorithm.

Portal "Eternal youth" http://vechnayamolodost.ru 25.09.2014

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