How brain implants can help paralyzed people

Even such a simple movement, like raising a cup of tea, requires a lot of action from your body. The arms should work to move it to the cup. The muscles of your palm should open so that you can grab the cup, and then close your fingers around to hold it. Then the muscles of the shoulder should hold the hand so that it does not flinch because of the extra weight of the cup. All these muscles should work accurately and in a coordinated manner, while you think you just made your tea.

How to get paralyzed muscles working?

That is why it is so difficult to make the paralyzed limb move again. Most paralyzed muscles can still work, but their connection to the brain has been lost, so they do not receive instructions for action. Unfortunately, doctors have not yet learned how to repair spinal cord injuries, but there is a solution. We can bypass it and give instructions to the muscles artificially. Thanks to the development of technologies for reading and interpreting brain activity, these instructions can one day come straight from the patient's head.

We can make the paralyzed muscles work by stimulating them with electrodes located inside them or around the nerves that supply them. This technology is known as "functional electrical stimulation". It can be used not only to help paralyzed people move, but also to restore the functions of the bladder, to stimulate an effective cough, and also to relieve pain. This technology can be of great importance for the lives of people with spinal cord injuries.

Research of scientists

Dimitar Blanc and her colleagues are working on how to combine this technology with a complex set of instructions required for the operation of one hand. If you want to raise a cup of tea, which muscles need to be stimulated, when and how much? These instructions are very complex, and not only because of the large number of muscles that are involved here. As you drink tea, these instructions will change, as the weight of the cup will decrease. In order to do something different, for example, scratch your nose, the instructions will be completely different.

Instead of simply testing various instructions on paralyzed muscles in the hope of finding those that will work, scientists use computer models of the musculoskeletal system to calculate them. These models are mathematical descriptions of how muscles, bones and joints act during movements. When modeling, it is possible to make the muscles stronger or weaker, paralyzed or stimulated from the outside. Therefore, it is possible to quickly and safely test various impulse models to see which ones are more successful.

Modeling of muscles

To test the technology, scientists implanted 24 electrodes in the muscles and nerves of the participants in the study. They used the simulation to decide where to place the electrodes, since the paralyzed muscles are larger than the electrodes in modern systems of functional electrical stimulation.

If you had a choice, which muscles are better to stimulate: subscapular or supernumerary? If you need to stimulate the axillary nerve, then where should you place the electrode? To answer these complex questions, scientists used modeling with different sets of electrodes, and chose one that allowed the computer model to perform the most effective movements.

Currently, the team is working on the shoulder, which is stabilized by a group of muscles called a rotating cuff. If the instructions that you receive to it are incorrect, the hand may pop out of the shoulder. That's why computer models are indispensable in this study. No one would have decided to put such experiments on the participants.

New tasks

Knowing how to activate paralyzed muscles to produce useful movements is only half the problem. Scientists also need to decide at what time to activate the muscles, for example, when the user wants to pick up some object. One of the possible options is the transmission of this information directly from the brain. Recently, researchers from the US have used an implant to listen to individual cells in the brain of a paralyzed person. Since different movements are associated with different forms of brain activity, the participant could choose one of six pre-programmed movements that were then generated by stimulation of the arm muscles.

Reading the Brain

Although this is an exciting step forward in the field of neural prosthetics, many problems remain unresolved. Ideally, brain implants should work for many decades. But at the present time it is difficult to record even those signals that will be needed for several weeks, so these systems should be calibrated regularly. The use of new implant designs or various brain signals can improve long-term stability.

In addition, implants listen to only a small part of the millions of cells that control our limbs, so the range of movements can be quite limited. Nevertheless, the control of the robotic limbs with a certain degree of freedom was nevertheless achieved, and the possibilities of this technology are developing rapidly.

The future of technology

And finally, smooth, effortless movements, which we take for granted, are guided by a rich sensory feedback system that communicates the brain where our hands are and when our fingers touch objects. These signals can be lost after trauma, so researchers are also working on brain implants that can restore sensations, as well as movements.

Some scientists believe that brain reading technology can help efficient people interact more effectively with computers, mobile phones and even directly with the brain of other people. Nevertheless, now it remains in the field of science fiction, while control of the brain for medical application is rapidly becoming a clinical reality.