Eyes witness new hues for the first time

Five people witnessed a strong green colour that has never been seen in humans before, thanks to devices that could allow them to experience typical vision.

It recognizes color through the retina behind the eyes. This absorbs each of three types of photodetector cone cells (called S, M, L) that usually absorb the blue, green, or red ranges and send signals to the brain. When you see something on the blue-green edge of the visible spectrum, there is a overlap in the wavelengths you detect, which activates at least two types of cone cells simultaneously.

ren ng At the University of California, Berkeley, I wondered what colour people perceived, whether or not only one type of cone is activated in this part of the spectrum. He was inspired by a device called the OZ, developed by other researchers studying how the eyes work, using lasers that can stimulate single cone cells.

Ng and his colleagues, including the scientist who built the OZ, upgraded the device so they could supply light to a small square patch of about 1,000 cone cells in the retina. Stimulating a single cone cell does not produce enough signals to induce color perception, says Ng.

Researchers tested five upgraded versions, only stimulating M-cones in this small area of ​​one eye, while the other eye was closed. Participants said they saw the blue-green colour the researchers called Oro. “It’s difficult to explain. It’s very wonderful,” says NG who also saw Oro.

To confirm these results, participants underwent a color matching test. I looked at the second colour until it matches as closely as possible the olo and the second colour that each could tune into any shade on the standard visible spectrum via the dial. They all dialed until it turned violent blue-green.

In another part of the experiment, participants used the dial to add white light to either the oro or the vibrant teal until it was closer to match. All participants diluted Oro. This supports more intense among the two shades.

Andrew Stockman At University College, London describes the study as “a kind of fun,” but with potential medical consequences. For example, the device can one day allow people with red-green color blindness to experience typical vision, which is difficult to distinguish between these colors. This is because conditions can be caused by both M and L cones, which are activated by light wavelengths with very similar states. Stockman said this should be tested in exams, but if you stimulate one more than others, people could be able to see a wider range of shades.