Brain prosthesis that may restore some vision shows promise in monkeys

Scientists have for the first time used a high-definition brain prosthesis to stimulate shape perception in monkeys, demonstrating the technology's potential as an aid for the blind.

Researchers hope the the breakthrough technology, detailed Thursday in the journal Science, can eventually be used to restore the vision of the more than 40 million people globally who are visually impaired.

It's not the first time scientists have used micro-stimulation of the visual cortex to trigger artificial vision. Experiments in both animals and humans have proven electrical stimulation of the visual cortex can produce the perception of a fleeting flash of light, called a phosphene.

Scientists have previously developed cortical visual prostheses, or CVPs, to trigger specific neurons and generate phosphene perceptions of different proportions and in different locations.

However, these devices have been limited by the position of their electrodes and their power demands, allowing only the stimulation of rather crude visuals.

To design a CVP capable of generating higher definition images, researchers fabricated arrays of silicon micro-electrodes arranged in a matrix-like pattern.

"[Our CVP] consists of 16 arrays with 64 electrodes each so that the total number of electrodes is 1,024," study co-author Pieter Roelfsema, researcher at the Netherlands Institute for Neuroscience, told UPI in a news release. "These arrays are 'shot' into the cortex with a pneumatic device."

For the study, researchers installed the novel brain implants in a pair of macaque monkeys trained to recognize shapes.

"We trained the monkeys to recognize letters. They made an eye movement to the right for an A, an eye movement to the left for a B when they saw these letters," Roelfsema said. "At some point, we directly stimulated patterns in the cortex without presenting any letters visually and were excited that they could recognize them."

Subsequent tests showed their implants were capable of stimulating perception of orientation and motion.

Now, Roelfsema and his colleagues and working to ensure the technology is ready for use in visually impaired humans.

"We will need to make sure that the electrodes keep working for many years, which will take hopefully one or two years," he said. "Then we need to make the entire system wireless. We hope to test it in humans in 2023."

In the near future, Roelfsema expects CVP technology to return rudimentary vision to the blind -- with definition between 5,000 and 10,000 pixels.

"We expect that this might be enough to navigate through traffic," he said.

Though cortical visual prostheses could soon make daily life a bit easier for the visually impaired, Roelfsema said it could be a while before the technology can help the blind stream movies inside their head.

"That will take many years," he said. "We are now producing 1,000 pixels in perception and hope to scale it up to 10,000. The human eye has 1,000,000 pixels, so we are not even close to this."

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