Although female squirrel monkeys can see in color, male squirrel monkeys are usually red-green colorblind because they do not have certain pigments in their retinas that detect those wavelengths of light. The only way these monkeys might be able to see red and green light is if they are treated with a gene therapy test. From this, they would be able to hopefully produce the protein needed for them to form a red photoreceptor cell which will allow them to detect the colors red and green.
With this theory, researcher Jay Neitz of the University of Washington in Seattle has taken two male monkeys, named Sam and Dalton, to perform a gene therapy test to see if they could produce the proteins they need to be able to see red and green lights. Since Sam and Dalton were both lacking the red photoreceptor cell, they were given injections with a virus carrying a gene with the protein. Over a 20 week period, the levels of protein slowly rised in the retinal cells of both monkeys and their performance on their daily color vision tests improved. While looking at a gray screen with red and green dots lighting up, Sam and Dalton were able to sense the difference of lights by pointing to where they were on the screen. Two years after Sam and Dalton underwent this test, they have maintained full color vision and can recognize all colors of light.
Researchers were very impressed that this test worked on adult monkeys and that it did not require any rewiring of the brain. Even though we do not know what actual colors the monkeys are seeing, scientists do know that they do have a change in what type of color they see through their new photoreceptors. Many scientists are now curious to see if this test would work on colorblind humans, but the outcome would be unpredictable.
By E.R.
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