Electrical stimulation improves arm control in paralyzed monkeys

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

Source: University of Pittsburgh

Electrical stimulation of surviving nerves in the upper spinal cord damaged by severe injury may improve upper extremity motor control and allow people with limited arm function to partially regain lost motion, report researchers from the University of Pittsburgh.

The first set of preclinical experimental data has been published in Natural neuroscience today.

“To perform even the simplest arm movement, our nervous system has to coordinate hundreds of muscles, and replacing this complex neural control with direct electrical muscle activation would be very difficult outside of a lab,” the researcher said. senior author Marco Capogrosso, Ph.D., assistant professor of neurological surgery and member of Pitt’s Rehabilitation and Neural Engineering Laboratories.

“Instead of stimulating muscles, we simplified the technology by designing a system that uses surviving neurons to reestablish the connection between the brain and the arm via specific stimulation pulses to the spinal cord, potentially allowing a paralyzed person to perform tasks of daily living. ”

Mobility deficits of the arms and hands, ranging from limitations in wrist flexion to the inability to move the arm, are among the most upsetting complications that stroke patients and paralyzed individuals are forced to face. .

Even mild deficits in arm and hand function significantly limit patients’ quality of life and autonomy, making the restoration of upper limb control an important focus in the field of neurorehabilitation.

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

A wide range of upper limb movement and superior dexterity distinguish primates and humans from other mammals. The ability to rotate the arm in 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 of how we holding objects and interacting with the world differently. This amazing ability is also what makes restoring movement to the arms and hands extremely difficult.

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

To test the technology, the researchers worked with macaque monkeys with partial arm paralysis who were trained to reach, grab and pull a lever to receive their favorite treat.

In addition to brain implants sensing electrical activity from regions controlling voluntary movement, the monkeys were implanted with a small array of electrodes connected to an external eraser-sized stimulator, which were switched on so transient when brain electrodes have detected the animal’s intention. move his arm.

“Our protocol consists of simple stimulation patterns that are initiated by sensing the animal’s intention to move,” said co-first author Sara Conti, Ph.D., at Harvard Medical School and at Boston Children’s Hospital.

“We don’t need to know where the animal wants to move; we only need to know that they want to move around, and extracting this information is relatively simple. Our technology could be implemented in clinics in different ways, potentially without requiring brain implants.

Even mild deficits in arm and hand function significantly limit patients’ quality of life and autonomy, making the restoration of upper limb control an important focus in the field of neurorehabilitation. Image is in public domain

The design and placement of the electrodes and the stimulator – on the nerve roots that grow from the spinal cord to the muscles of the arm and hand – have been extensively verified using a combination of computational and computer algorithms. medical imaging, ensuring that each animal’s unique anatomy was compatible with the device.

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

“Step back and tackle a very complex clinical problem from a different and simpler perspective than 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., a former doctoral student at the University of Friborg in Switzerland and a visiting scholar at Pitt, currently at New York University.

“By building technology around the nervous system that mimics what it is naturally designed to do, 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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The other authors of this article are Matthew Perich, Ph.D., and Tomislav Milekovic, Ph.D., both of 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., Stéphanie Lacour, Ph.D., Jocelyne Bloch , Ph.D., and Grégoire Courtine, Ph.D., all at the Ecole Polytechnique Fédérale de Lausanne, Geneva.

Funding: This research was supported by a grant from the Wyss Center (WCP008), ONWARD Medical, the Bertarelli Foundation, the Swiss National Science Foundation Ambizione Fellowship (#167912) and the Doc-Mobility Grant (188027), the Research and Development Program Horizon 2020 innovation from the European Union under the Marie Skłodowska-Curie scholarship agreement (665667), a scholarship from the Swiss National Fund (BSCGI0_157800), a scholarship from the Whitaker International Scholars Program and internal funding from the University of Friborg and pitt.

About this neurotechnology research news

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

Original research: Access closed.
Epidural Electrical Stimulation of Cervical Dorsal Roots Restores Voluntary Upper Limb Control in Paralyzed Monkeys” by Marco Capogrosso et al. Natural neuroscience


Epidural Electrical Stimulation of Cervical Dorsal Roots Restores Voluntary Upper Limb Control in Paralyzed Monkeys

Regaining control of the arm 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 harnessed 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 exploits the functional organization of the dorsal roots to transmit artificial excitation by electrical stimulation to the spinal segments concerned during the appropriate phases of movement. Bursts of stimulation targeting specific segments of the spine produced sustained arm movements, allowing arm-paralyzed monkeys to perform a reach-and-grasp task without restraint.

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

The efficacy and reliability of our approach holds realistic promises of clinical translation.

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