Prosthetics for the blind? Electrodes let monkeys see colors, contrast

A new study that reveals what monkeys see when a part of their brain receives electrical stimulation could lead to neuroprosthetics that help blind people 'see' again.
Written by Janet Fang, Contributor

A new study reveals what monkeys see when a part of their brain receives electrical stimulation.

The discovery could help scientists create a prosthetic device to restore vision to the blind based on direct stimulation to certain visual processing areas of the brain.

So, you know how sometimes you stand up too fast or your hit your head, and you see stars? These perceptions – or ‘phosphenes’ – are experienced by people even if their eyes are closed or they’re blind, New Science explains.

Well, a team led by MIT’s Peter Schiller stimulated the areas of the monkey brain that process visual information to figure out what the phosphenes look like to 2 rhesus monkeys named Hank and Malibu.

  1. First, they trained the monkeys (using apple juice) to direct their gaze to the bigger or brighter of 2 figures on a computer screen.
  2. Then they inserted tiny electrodes into their brains. Specifically, into their primary visual cortex – the part that stays intact for many years even after damage to the eyes that cause vision loss.
  3. They stimulated the monkeys’ brains through the electrodes while they performed tasks that involved shifting their eyes between 2 objects.
  4. For size and contrast, one of dots on the screen was periodically replaced with electrical stimulation (in other words, one of dots was replaced by an electrically generated phosphene). When the monkey’s gaze moved towards the phosphene, the star must be bigger or have higher contrast than the dot.
  5. For color, the researchers shifted the background image prior to the appearance of a single object or electrical stimulation. When the background had the same color and contrast as the image created by electrical stimulation, the monkeys couldn’t see the target and didn’t shift their gaze.

Turns out, the stars were between 9 to 26 arc minutes (1 arc minute is 1/60th of a degree) in diameter, and New Scientist reports, appeared in a variety of colors, including pink, blue, green, and yellow.

"We want to understand the brain to help the blind," Schiller says. His goal is to pair electrical stimulation of the visual cortex with a small camera, allowing researchers to stimulate the visual cortex with a pattern of activity that translates the information captured by the camera – giving a kind of sight to blind people.

They propose to supply the electrical messages that the brain interprets as an ‘image’ directly to the brain's visual cortex, the Los Angeles Times reports. But first, they’ll need to translate complex visual images into electrical signals that convey the density of information we expect – not only the shapes and colors of objects but also their distance from us.

The study was published in the Proceedings of the National Academy of Sciences this week.

Image by >>V<< via Flickr

This post was originally published on Smartplanet.com

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