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Monkeys Use Their Minds to Move Virtual Arms

  • Jessica Berman

Large-scale brain activity from a rhesus monkey was decoded and used to simultaneously control reaching movements of both arms of a virtual monkey avatar towards spherical objects in virtual reality. Photo: Duke Center for Neuroengineering

Large-scale brain activity from a rhesus monkey was decoded and used to simultaneously control reaching movements of both arms of a virtual monkey avatar towards spherical objects in virtual reality. Photo: Duke Center for Neuroengineering

Researchers have developed an interface between a monkey’s brains and a machine that could eventually be used to allow someone with a spinal cord injury to control an artificial arm or leg simply by thinking about it.

Initially, interfaces developed by researchers at Duke University’s Center for Neuroengineering in Durham, North Carolina, could control only a single prosthetic limb.

Now, the scientists have developed an interface that allows rhesus monkeys to move two arms at the same time, as they watch an avatar - a likeness of themselves - on a computer screen.


Virtual monkey avatar shown from a 3rd person perspective as the movements of the two arms are decoded in real-time from the brain of a rhesus monkey. In the experiment the virtual arms and 3D target objects appear on the screen from a first-person perspective to the monkey, who receives a juice reward for correctly performed trials. Source: Duke Center for Neuroengineering

Neurobiology professor Miguel Nicolelis said the monkeys first learned to control the avatar with a pair of joysticks, but then were trained to stay completely still.

“They are trained not to move their arms,” Nicolelis said. “They are trained just to imagine the movements. And we get the signals from both parts of their brains - both hemispheres - to be routed to a computer that’s running a computer algorithm that translates their voluntary will to move into movements of a virtual body.”

Researchers measured the activity of 500 neurons in two monkeys involved in the planning of motor behaviors from multiple areas in both of their brain's cerebral hemispheres. Nicolelis said this neural activity is much more complicated than that involved in moving each arm separately.

As the monkeys became more skilled at using their brains to move their virtual arms, researchers saw signs of brain plasticity or neuronal growth, a possible sign the monkeys were incorporating the virtual arms into their own mental image.

Nicolelis said scientists are now developing a brain-controlled neuroprosthetic vest to allow the wearer to control prosthetic devices. The device translates the electrical signals from the brain into motor commands and eventually digital signals that a machine inside the vest can read.

Nicolelis said the vest will be unveiled at the 2014 World Cup in Brazil.

“And we hope to make a demonstration during the opening ceremony by having a young paraplegic, a Brazilian adult, to walk into the field using this vest, wearing this vest, controlled by brain activity and being in charge of the opening kick-off of the World Cup,” he said.

The vest could potentially help people with spinal cord injuries, and also paralysis caused by a number of diseases.

An article on rhesus monkeys using their minds to control virtual arms is published in the journal Science Translational Medicine.

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