Early humans were extremely talented hunters, so it's only natural that our visual systems evolved to maximize our prey -- while an unchanging landscape wasn't particularly of interest, a deer leaping from the meadows would get the brain's visual cortex all flared up. When a person goes blind, this portion of the brain is usually unharmed but is fairly useless since it doesn't receive any information from the eyes.
This neural emphasis on movement could be the key to restoring sight to blind people, which is why, inspired by this connection, a team of researchers has bypassed the eyes and instead produced perceivable images by directly activating the brain's visual cortex with a device.
In the breakthrough study which utilized this technique, a blind test participant was able to recognize letters and silhouettes of shapes.
'Seeing' with a brain implant
The experimental device, which has been detailed in a paper recently published in The Journal of Clinical Investigation, includes a forward-facing "artificial retina" put on a pair of glasses. The device detects light from the visual field in front of the glasses and converts it into electrical signals. These are then sent to a three-dimensional matrix of 96 micro-electrodes that is implanted in the user's brain, which penetrate it to stimulate and monitor the electrical activity of neurons in the visual cortex. Each of the tiny electrodes is 1.5 mm long, and the implant is only 4 mm wide, and they can both activate and monitor the electrical activity of neurons in the visual cortex since they penetrate the brain. Light patterns are transmitted to the artificial retina, which is stimulated, allowing the individual to perceive them.
While this device was successfully tested with a 1,000-electrode version of the system on primates, the animals were not blind, which had caused debates on the feasibility of the device. However, a team from Spain's Miguel Hernández University has recently put the current version to the test on a 57-year-old woman who had been blind for almost 16 years.
The woman was able to recognize letters and the outlines of specific information after a period of training during which she learned to understand visuals produced by the device.
Another significant outcome of the study was that the implant did not impair the function of the cerebral cortex in any way, nor did it excite nearby non-target neurons. Furthermore, compared to identical electrode arrays put on the surface of the brain, the implant required far less electrical current which makes it potentially safer to use.
Six months after the implantation, the device was removed, and today, the reported advancements are offering hope to thousands of blind individuals around the world. While it'll be some time before the technology can be scaled up, more experiments are underway, and they'll involve stimulating a larger number of neurons at the same time in order to get to more complex visuals.