Electrical stimulation improves arm control in paralyzed monkeys

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Electrical stimulation of surviving nerves of the upper spinal cord damaged by severe injury may improve upper limb motor control and enable individuals with limited arm function to partially regain lost movement, University of Pittsburgh researchers report. The first round of preclinical experimental data was published in Nature Neuroscience Today.

“To perform even the simplest arm movement, our nervous system has to coordinate hundreds of muscles, and replacing this intricate neural control with direct electrical muscle activation would be very difficult outside of a lab,” said senior author Marco Capogrosso, Ph.D., assistant professor. professor of neurological surgery and member of the Rehabilitation and Neural Engineering Labs in Pitt. “Instead of stimulating muscles, we simplified the technology by designing a system that uses surviving neurons to restore the connection between the brain and the arm via specific stimulation pulses to the spinal cord, enabling a person with paralysis to perform tasks of daily living.” can perform life.”






Electrical stimulation of the nerve roots arising from the spinal cord to the muscles of the arm and hand improves precision, strength and range of motion in animals with cervical spinal cord injuries. Credit: Marco Capogrosso, University of Pittsburgh

Deficits in arm and hand mobility — ranging from limitations in bending the wrist to the inability to move the arm — are some of the most life-changing complications faced by patients and those who have become paralyzed. Even mild impairments in arm and hand function significantly limit patients’ quality of life and autonomy, making the restoration of upper limb control a major focus of neurorehabilitation.

Yet there are no therapies or medical technologies that would allow patients to restore or meaningfully improve their lost upper limb function.

A wide range of upper limb movements and superior agility distinguish primates and humans from other mammals. The ability to rotate the arm at the shoulder, bend it at the elbow, flex and extend the wrist, and alter the grip by changing the position of individual fingers allows for extraordinarily complex control over the way we view objects. holding and interacting with the world in a different way. That amazing ability is also what makes restoring arm and hand movements extremely difficult.

Pitt researchers faced a challenging task: to develop a technology that could activate the remaining healthy nerves connecting the brain and spinal cord to control the muscles of the arm using external stimuli. The technology also had to be seamless and require little to no training to use, allowing the individuals to continue familiar motor tasks as they did before their injury.

To test the technology, researchers teamed up with macaque monkeys with partial arm paralysis who had been trained to reach, grasp and pull a lever to receive their favorite food treat.

In addition to detecting brain implants: electrical activity from regions that controlled voluntary movement, the monkeys were implanted with a small array of electrodes connected to an external stimulator the size of a pencil eraser, which turned on momentarily when brain electrodes detected the animal’s intention to move its arm.

“Our protocol consists of simple stimulation patterns initiated by sensing the animal’s intention to move,” said co-first author Sara Conti, Ph.D., of Harvard Medical School and Boston Children’s Hospital. “We don’t need to know” Where the animal wants to move; we just need to know that they want moving, and extracting that information is relatively easy. Our technology could be implemented in many different ways in clinics, possibly without the need for brain implants.”

The design and placement of the electrodes and stimulator – over the nerve roots sprouting from the spinal cord to the muscles of the arm and hand – were extensively verified using a combination of computer algorithms and medical imaging to ensure each animal’s unique anatomy. was compatible with the device.

The analysis showed that, while not enough to fully restore arm function, stimulation significantly improved precision, strength and range of motion, allowing each animal to move its arm more efficiently. Importantly, the animals continued to improve as they adapted and learned how to use stimulation.

“Taking a step back and addressing a very complex clinical problem from a different and simpler perspective compared to anything that has been done before opens up more clinical possibilities for people with arm and hand paralysis,” said co-first author Beatrice Barra, Ph. D. , former doctoral student at the University of Friborg in Switzerland and visiting researcher at Pitt, currently at New York University. “By building a technology around the nervous system mimicking what it’s naturally designed for, we get better results.”

A clinical trial testing whether electrical spine stimulation could improve arm and hand control in stroke patients, recruits participants from the University of Pittsburgh and UPMC.


Electrical stimulation improves the function of paralyzed patients


More information:
Marco Capogrosso, Epidural Electrical Stimulation of the Cervical Dorsal Roots Restores Voluntary Upper Limb Control in Paralyzed Monkeys, Nature Neuroscience (2022). DOI: 10.1038/s41593-022-01106-5www.nature.com/articles/s41593-022-01106-5

Quote: Electrical Stimulation Improves Arm Control in Paralyzed Monkeys (2022, June 30) retrieved June 30, 2022 from https://medicalxpress.com/news/2022-06-electrical-arm-paralyzed-monkeys.html

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