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A small step for monkeys is a giant leap toward helping paralyzed people walk again

Gregoire Courtine holds a silicon model of a primate’s brain and a brain implant. The brain-spine interface uses a microelectrode array like this one to detect spiking activity of the brain’s motor cortex.
(Alain Herzog / EPFL)

A rhesus monkey whose spinal cord was partially severed quickly regained control over his paralyzed leg after researchers implanted an electronic device below the site of the spinal injury.

That pulse generator sent out electrical signals that commanded the monkey’s leg to move, and the affected leg responded as early as six days after it was paralyzed. The signals to move were commands collected from the motor cortex of healthy rhesus monkeys as they freely walked and used their legs.

Together, the two devices leaped over the broken connection between brain and limb, allowing the partially paralyzed monkey to mimic key walking motions, according to a study published Wednesday in the journal Nature.

The brain-spine interface offers new hope that patients who have lost function of a limb due to a spinal cord injury might be able to restore that function and prevent the degeneration of the neural wiring that is needed for an eventual return to movement.

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Researchers have already demonstrated they can use signals decoded from the brain’s motor cortex to control the movement of a prosthetic hand — and even to reanimate a patient’s own paralyzed hand.

But walking is more complex, involving the coordinated activation of many more muscles. This marks the first time such a constellation of techniques and technologies has been used to restore complex leg movements in a non-human primate.

The authors of the new research, led by scientists from the Swiss Federal Institute of Technology, have already begun testing components of the interface in humans with partial spinal cord injuries in Switzerland. Worldwide, between 250,000 and 500,000 people suffer spinal cord injuries each year and suffer some degree of paralysis.

A close-up view of the pulse generator that allowed a paralyzed monkey to walk.
A close-up view of the pulse generator that allowed a paralyzed monkey to walk.
(Alain Herzog / EPFL )

The use of so-called brain-machine interfaces is a rapidly developing piece of the effort to help patients who have paralysis or are “locked in” by brain disease. Researchers are scrambling to develop ever-more-sensitive tiny electrical arrays to record brain activity, and to hopscotch over the spine’s broken communication networks to transmit those messages to muscles.

The experiment reported in Nature harmed two of nine male monkeys, surgically cutting their spinal cords to effect paralysis in one leg. The procedures were conducted in China, where animal protection measures are not as stringent as those in the United States or Europe. The research did conform to standards that apply in the European Union.

melissa.healy@latimes.com

Follow me on Twitter @LATMelissaHealy and “like” Los Angeles Times Science & Health on Facebook.

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