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Scientists are taking another step towards restoring sight to the blind, having built an implant that bypasses the eyes and allows monkeys to perceive artificially induced patterns in their brains.
The technology, developed by a team from the Netherlands Institute for Neuroscience (NIN), was described in the journal Science on Thursday.
It is based on an idea first conceived decades ago: to electrically stimulate the brain to “see” points of light called phosphenes, which can also be thought of as artificial pixels.
But the concept never achieved its full potential due to technical limitations.
A team led by NIN director Pieter Roelfsema developed implants consisting of 1,024 electrodes wired into the visual cortex of two sighted monkeys, resulting in a much higher resolution than previously achieved.
The visual cortex is located at the back of the brain and many of its features are common to humans and other primates.
“The number of electrodes that we have implanted in the visual cortex, and the number of artificial pixels that we can generate to produce high-resolution artificial images, is unprecedented,” Roelfsema said.
This allowed the pair of monkeys to distinguish shapes like letters of the alphabet, moving lines and dots, which they had previously been trained to respond to by moving their eyes in a particular direction to earn a reward.
The monochrome patterns are still rudimentary compared to real vision, but represent a major leap from previous implants, which allowed human users to determine only vague light and dark areas.
Roelfsema said his team now had a “proof of principle” that laid the foundation for a neuroprosthetic device for the 40 million blind people around the world.
This could be a camera the user is wearing or a pair of glasses, which uses artificial intelligence to convert what they see into a pattern that they can send to the user’s brain. .
Similar technology has appeared in science fiction works, such as the visor worn by Geordi La Forge on “Star Trek: The Next Generation”.
Writing in a related commentary, Michael Beauchamp and Daniel Yoshor of the University of Pennsylvania hailed the breakthrough as a “technical tour de force.”
The NIN team took advantage of advances in miniaturization and also developed a system to ensure that their input currents were large enough to create visible dots, but not to the point that the pixels got too large.
They did this by placing certain electrodes at a more advanced stage of the visual cortex, to monitor the amount of signal passing through, and then adjust the input.
– The future of wireless –
Roelfsema said his team hoped to make similar devices for humans in about three years.
But the electrodes used by the team require silicone needles that work for about a year before tissue builds up around the needles and they stop working.
“So we want to create new types of electrodes that are better accepted by the body,” he said.
Ultimately, a wireless solution would be best, as it would mean that the user would not need to wear an implant on the back of their skull.
Prostheses would only be suitable for people who once had their sight and subsequently lost it due to illness or injury.
The brains of people born blind devote the visual cortex to other functions. But in people whose eyes no longer work, the visual cortex remains inactive.
© 2020 AFP
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