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Across the world, more than 40 million people are affected by blindness. In an increasingly digitized culture where more interactions rely on vision and touchscreens, it can become a significant challenge.
A critical human sense could be restored after positive tests on monkeys
Scientists are designing an implant for monkeys that could one day help restore vision to the blind.
by Sarah WellsTechnologies to compensate for limited sight have come a long way from the invention of Braille in the 1800s, but scientists are hoping to still take this a step further and restore vision altogether.
In a new study, a team of neuroscientists has demonstrated how such a vision-restoration device might work in monkeys, using an implant that sends painless electric signals to the brain to create bursts of light. Those bursts of light could one day be beamed from glasses that can translate the visual world into sensory cues. People with vision impairments could possess a form of vision.
The background — In 1950, scientists discovered that electrical stimulation to the visual part of the brain could create distinct, bright bursts of light called "phosphenes." In the decades since, researchers have been trying to transform these brief flashes of light into sustained visual information.
Phosphenes are brief flashes of light that can be stimulated in the brain.
What's new — Earlier this spring, a team of neuroscientists demonstrated the use of these light bursts using subdermal implants (ones that are just under the skin) to stimulate sequential phosphene flashes. In these trials, a number of participants with visual impairments were able to "see" flashes — and trace their shapes on a board.
But the authors of a new study write that this breakthrough solved only part of a larger problem.
"[S]equential stimulation limits the amount of information that can be transferred per unit of time," write the authors in their paper.
"The generation of shapes via simultaneous electrical stimulation of multiple electrodes in the visual cortex remains to be demonstrated." In other words, scientists have yet to stimulate these flashes all at once, which will be necessary for clearer, more realistic images in the future.
And this is exactly what the research team set out to solve in their monkey trials. For two monkey participants, L and A, scientists implanted an intracortical device (where electrodes actually penetrate the brain) designed to send out electric stimulation simultaneously from over 1000 tiny electrodes to depict shapes, motion, or letters.
"These developments place a light at the end of the tunnel for those without sight."
The research was published Thursday in the journal Science.
How it works — In natural vision, information from visual scenes (like watching a dog play fetch) are sifted through different processing parts of your brain before they become the adorable image with which we're familiar. Two important tools used in this process are the primary visual cortex (V1) and higher-order visual areas like the fourth visual area (V4.)
It is in these two areas in the monkeys' brains that scientists planted the electrodes.
"Our implant interfaces directly with the brain, bypassing prior stages of visual processing via the eye or the optic nerve," explains Xing Chen, now a senior researcher at the Netherlands Institute for Neuroscience and first author on the study.
"In the future, such technology could be used for the restoration of low vision in blind people who have suffered injury or degeneration of the retina, eye, or optic nerve, but whose visual cortex remains intact."
The researchers ran several different trials to see how well the monkeys could recognize motion, shapes, and letters when stimulated through the implant.
The results — The results were not necessarily perfect, but the researchers report that the monkeys performed better in the trials than they had expected and often above just chance.
"Humans report that phosphenes induced by stimulation of early visual cortical areas vary in color, brightness, shape, and perceived distance," explain the authors.
"We expected the accuracy for the tasks with electrical stimulation to be worse, because it is not possible to control the appearance of individual phosphenes."
What's next — The researchers say there are still a number of technical hurdles to overcome before this tech can be tested on people. Among those challenges are extending the visual range for stimulation and designing a wireless implant.
Nevertheless, they are excited by what advances in this technology could mean for those without sight.
"Much progress is being made in the development of brain-computer interfaces for sensory restoration and motor prostheses," the authors write.
"Combined with the present demonstration of artificial vision, these developments place a light at the end of the tunnel for those without sight."
Abstract: Blindness affects 40 million people across the world. A neuroprosthesis could one day restore functional vision in the blind. We implanted a 1024-channel prosthesis in areas V1 and V4 of the visual cortex of monkeys and used electrical stimulation to elicit percepts of dots of light (called phosphenes) on hundreds of electrodes, the locations of which matched the receptive fields of the stimulated neurons. Activity in area V4 predicted phosphene percepts that were elicited in V1. We simultaneously stimulated multiple electrodes to impose visible patterns composed of a number of phosphenes. The monkeys immediately recognized them as simple shapes, motions, or letters. These results demonstrate the potential of electrical stimulation to restore functional, life-enhancing vision in the blind.
See also: Blindsight: can a strange neurological condition explain consciousness?
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