Spatio-temporal neuromodulation

St. Petersburg State University Press Service 

In the course of a large-scale study, an international group of scientists managed to develop a new effective method of electrostimulation of the spinal cord in paralysis. After testing the effectiveness of the method on rodents, the researchers came to the conclusion that it could be used in humans to restore sensorimotor functions. The head of the Laboratory of Neuroprostheses of the Institute of Translational Biomedicine of St. Petersburg State University, senior researcher of the I. P. Pavlov Institute of Physiology of the Russian Academy of Sciences, Head of the Laboratory of Neurophysiology and Experimental Neurorehabilitation of the Research Institute of Phthisiopulmonology of the Ministry of Health of the Russian Federation, Doctor of Medical Sciences, Professor Pavel Musienko took an active part in the work of the scientific group.

Today, more than 2 million people in the world cannot move as a result of severe spinal injuries. Every year there are about 50 thousand paralyzed patients. The fight against diseases and the treatment of spinal cord injuries is a complex medical, social and economic task, the relevance of which is noted by experts.

Previously, as a result of animal experiments and clinical studies, it was shown that neuromodulation of lumbar segment networks using electrical stimulation improves movement control after spinal cord injury. However, this method had two main limitations. Firstly, until now it was possible to influence only certain areas of the spinal cord. Secondly, the stimulation occurred continuously throughout the entire motor activity and was not tied to a specific moment of muscle activity.

"Today we have learned how to control the contraction of certain muscle groups involved in the movement process in real time," explained Pavel Musienko. – Thanks to the possibilities of computer modeling, we were able to identify those points of the spinal cord, the impact on which in the future will help solve the problem with the restoration of motor functions in humans."

In the course of the study, scientists have developed new stimulation protocols that reproduce the natural dynamics of motor neuron involvement and limb muscle contractions during movement. With the help of computer modeling, optimal positions of electrodes on the spinal cord were found to cause contractions of certain muscle groups. In turn, this model was the basis for the design of spinal electrode arrays and software control, which modulates the work of extensor and flexor muscles in real time and with high accuracy. Scientists have developed an algorithm for influencing several segments of the spinal cord, changing the electrical stimulation depending on the current motor abilities and the task being performed. Stimulation of specific segments of the left and right half of the spinal cord in rodents made it possible to control the activity of muscles of different limbs during movement. Such spatiotemporal neuromodulation effectively restored the quality of walking, the ability to support body weight, endurance and coordination when moving in rats with severe spinal cord injuries.

"During the research, we created new implantation technologies, electrode matrices and an algorithm for stimulating neural networks with fine tuning based on feedback from limb movements," Pavel Musienko said. "As it turned out, this approach, called "spatio–temporal neuromodulation", is much more effective than the ones we used earlier."

For the study, surgical methods were specially created, including vertebral orthosis for reliable fixation of devices on the spine, long-term functionality and good biointegration of the implant into the tissue. The effectiveness of these methods was confirmed during 6-week functional and morphological studies.

The developed technology opens up new opportunities for both fundamental research of the central nervous system and for neuroprosthetics in diseases and injuries. Scientists are convinced that this approach can be applied in the development of scientifically based neuromodulation methods for restoring motor activity in humans.

"Together with medical scientists from St. Petersburg State University, as well as colleagues from the Laboratory of Neurophysiology and Experimental Neurorehabilitation of the Institute of Phthisiopulmonology of the Ministry of Health of the Russian Federation, we are doing everything possible to transfer the developed technologies to the clinic as soon as possible," Professor Musienko stressed. – To date, several applications have already been submitted for complex projects on the subject of neuroprostheses, in particular in the RNF, RFBR and NeuroNet. The support of the state and private investors largely determines how soon it will be possible to introduce the developed neurorehabilitation approaches into medical practice in Russia."

Read more about the results of the study in the article Spatiotemporal neuromodulation therapies engaging muscle synergies improve motor control after spinal cord injury, Nature Medicine, January 18, 2016.

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27.01.2015