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Electrical stimulation improves arm control in paralyzed monkeys

Overview: Electrical stimulation of surviving nerves in the upper spinal cord after severe spinal cord injury improved motor control in the upper extremities and enabled monkeys with limited arm function to regain lost movement.

Source: University of Pittsburgh

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 it would be very difficult to replace this complicated neural control with direct electrical muscle activation outside of a lab,” said senior author Marco Capogrosso, Ph.D., assistant 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. †

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 at the elbow, flex and extend the wrist, and alter grip by changing the positions of individual fingers allows for extraordinarily complex control over the way we hold objects and interact 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 worked with partial-arm paralysis macaques trained to reach, grasp and pull a lever to receive their favorite food treat.

In addition to brain implants that detect electrical activity from regions that control 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 intent 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 clinics in many different ways, possibly without the need for brain implants.”

This shows a brain
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. Image is in the public domain

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 that mimics what it was naturally designed for, we get better results.”

A clinical trial testing whether electrical stimulation of the spinal cord could improve arm and hand control in stroke patients is recruiting participants from the University of Pittsburgh and UPMC.

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Other authors of this paper are Matthew Perich, Ph.D., and Tomislav Milekovic, Ph.D., both at the University of Geneva; Katie Zhuang, Ph.D., Mélanie Kaeser, Ph.D., Maude Delacombaz, Ph.D., Eric Rouiller, Ph.D., all at the University of Fribourg, Switzerland; Giuseppe Schiavone, Ph.D., Florian Fallegger, Ph.D., Katia Galan, Ph.D., Nicholas James, Ph.D., Quentin Barraud, Ph.D., Stephanie Lacour, Ph.D., Jocelyne Bloch , Ph.D., and Grégoire Courtine, Ph.D., all at the École Polytechnique Fédérale de Lausanne, Geneva.

Financing: This research was supported by a Wyss Center grant (WCP008), ONWARD Medical, the Bertarelli Foundation, Swiss National Science Foundation Ambizione Fellowship (No. 167912) and Doc-Mobility grant (188027), the Horizon 2020 research and innovation program from the European Union under the Marie Skłodowska-Curie Scholarship Agreement (665667), a scholarship from the Swiss National Foundation (BSCGI0_157800), Whitaker International Scholars Program scholarship and internal funding from the University of Friborg and Pitt.

About this neurotech research news

Author: Anastasia Gorelova
Source: University of Pittsburgh
Contact: Anastasia Gorelova – University of Pittsburgh
Image: The image is in the public domain

Original research: Closed access.
Epidural electrical stimulation of the cervical dorsal roots restores voluntary upper limb control in paralyzed monkeysby Marco Capogrosso et al. Nature Neuroscience


Abstract

Epidural electrical stimulation of the cervical dorsal roots restores voluntary upper limb control in paralyzed monkeys

Regaining arm control is a top priority for people with paralysis. Unfortunately, the complexity of the neural mechanisms underlying arm control has limited the effectiveness of neurotechnological approaches. Here we used the neural function of surviving spinal circuits to restore voluntary arm and hand control in three monkeys with spinal cord injury, using spinal cord stimulation.

Our neural interface takes advantage of the functional organization of the dorsal roots to transfer artificial excitation via electrical stimulation to relevant spinal segments in appropriate phases of motion. Stimulation bursts targeting specific spinal segments produced sustained arm movements, allowing monkeys with arm paralysis to perform an unrestricted reaching and grasping task.

Stimulation specifically improved strength, task performance and movement quality. Electrophysiology suggested that residual descending inputs were required to produce coordinated movements.

The effectiveness and reliability of our approach hold realistic promises of clinical translation.

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