New findings challenge conventional dogma regarding brain plasticity after organ loss

Advances in neuro-science and engineering have given great hope to prosthetics like Luke Skywalker: robotic devices that are almost different from a human being.

The key to solving this challenge is to design devices that can not only be operated by the user’s own cloud functionality but also receive accurate and accurate sensing information to the user.

A new study by neuroscientists at the University of Chicago and Chalmers University of Technology, was published on Dec. 22 in the journal Cell reports, showing just how difficult this can be.

In a group of three subjects where the organs were replaced by neuromusculoskeletal prostate organs, the researchers found that, even after a full year of using the devices, subjective awareness did not shift. ever partner to match the position of the friction sensors on their prosthetic devices.

The stability of the sensing stimuli clarifies the limitations in the ability of the nervous system to adapt to different sensory inputs.

Three participants with above-the-shoulder amputations were equipped with high-tech neuroprosthetic devices attached directly to their humerus bone.

Users were able to control the prosthetic device thanks to signals received from electrodes implanted in the muscles of the left arm and received sensory feedback through another set of electrodes. which was applied. It was a sensation located on the prosthetic thumb that stimulated nerve stimulation, which caused a sensation of rubbing.

However, because the organization of the nerve is largely irregular, surgeons cannot be sure whether the position of the electrons will create a sensation in the right place on the thumb. In the study, prosthetic users did not report feeling the sensation on the thumb, but in other hand areas, such as the middle finger or palm.

Participants would then consume the prostate for up to 12 hours a day, every day, using it to handle items through their daily work for more than a year.

“One problem with conventional cloud electrons is that you can’t tell during implant surgery which part of the nerve responds to the sensation, so the electrons do not always lie in the exact position. a place in the nerve that would depend on the position of the sensors in a prosthetic arm, ”said lead author and developer of the neuromusculoskeletal prostheses, Max Ortiz Catalan, Ph.D., associate professor of bionics at Chalmers University of Technology and Director of the Center for Bionics and Pain Research in Gothenburg, Sweden.

“We hoped that with the patients grasping objects and feeling their sensation elsewhere in their hand, all day and every day for several months, their brain would resolve the problem. -balanced by moving the intended sensation to the thumb, “he continued.

Despite being able to see the hand while interacting with objects, none of the users ever mentioned that they felt the sensation on their thumb, but that the consciousness continues in the same area where it was originally felt.

“Every day, for a year, these subjects saw their prosthetic thumb rub on things and feel in a different place – sometimes close to the thumb, but not on – and not never felt the feeling. Not even a marrow, “said senior author Sliman Bensmaia, PhD, James Family Professor and Karen Frank in Organic Biology and Anatomy at UChicago.

These results challenge conventional dogma regarding brain plasticity after organ loss. Many believe that the brain has a high capacity to reorganize after it has lost sensory input, co-opting existing brain tension for other reasons.

This idea has been that the nervous system is truly plastic, so if you see an imbalance between what you see and what you feel, it is a good opportunity for neural remodeling. For example, if you sew two fingers together and look at how that is represented in the brain, it looks like they have come together. “

Sliman Bensmaia, PhD, Lead Author Study, James and Karen Frank Family Professor in Organic Biology and Anatomy, University of Chicago Medical Center

“But I think this idea has been overwhelmed. You’re less likely to reorganize a room and more likely to just hear an echo kicking around an empty room, “he continued.

“You may get some transcendental feeling from the nearby limbs, but it’s just because the area of ​​the brain that used to respond to consciousness is empty, and by activating the neurons around leading to an echo through the evacuation. “

This study highlights the importance of knowing exactly where to place electrons when installing sensory arrays for patients using these types of neuroprosthetic devices, as it does not appear to be the case. the brain is able to make major changes in how it perceives that sensory input. “This means you have to do it right,” Bensmaia said. “There’s no over here.”