Recent scientific work on campus has allowed mice to finally appreciate the red wheels they run on to pass the time.
The researchers, who also hailed from Johns Hopkins University School of Medicine, inserted into the mice’s chromosomes a single human gene that enables the rodents to see the color red. Mice can normally only see shades of blue and green.
The findings have implications for humans because it shows that mammals’ brains may be flexible to color change, thus a cure for colorblindness or enhancements to human color vision may be possible.
The study was published in the March 23 edition of the journal Science. Johns Hopkins molecular biology professor Jeremy Nathans worked on the genetic engineering aspect, while UCSB psychology professor Gerald Jacobs devised a test to determine whether it had been successful.
According to Jacobs, mice do not have the same evolved vision as humans – perhaps because it is not necessary for nocturnal animals to see the same variety of colors. Like most other mammals, they are dichromats, and can only distinguish between green and blue lights.
Humans and other primates, meanwhile, are trichromats and can also distinguish between green and red lights.
After Nathans inserted the human gene, Jacobs determined whether the mice could in fact see a broader range of colors by displaying two identical red lights and one blue light on three test panels.
Mice were rewarded with a drop of soymilk when they correctly identified the blue light. The genetically altered mice chose the blue panel in 80 percent of the trials, while the normal mice only chose the blue panel one-third of the time, corresponding with a pattern of random guessing.
Jacobs said the ability to see a broader spectrum of colors is evolutionarily advantageous because it is a quick way to differentiate between objects and it and facilitates vision at a distance. He said he is unsure whether it will prove sufficiently helpful to the mice to merit natural selection.
“One virtue of color as a source of information is that you can use it quickly and at a distance,” Jacobs said. “We don’t know if what we did to the mice would actually evolve. In order for it to be evolved, it has to be an advantage [to the mouse].”
The study indicates that mammals’ brains may be more flexible than previously believed. The mice learned to distinguish colors that their ancestors had never seen before without any change to the nervous system.
Jacobs said there has been ongoing academic debate over whether the mutation that allowed humans to experience the color red had to pass through many generations before humans had the actual ability to perceive the color. This experiment suggests that the nervous system can accommodate changes in a single generation.
“It shows that the nervous system has a lot of plasticity,” Jacobs said.
Some have theorized that the findings could lead to a cure for colorblindness, which affects 8 percent of males, or could even enhance the color spectrum humans are capable of seeing. Jacobs, however, is unsure if these improvements are possible.
“I don’t know that there are implications [for the visually impaired],” Jacobs said. “[However,] it is very likely that the nervous system could generate for the new color vision.”
As possible parallel to the future of these vision-enhanced mice, Jacobs said there is a percentage of women who have the ability to see extra colors – indicating that natural selection could lead toward more colorful vision.
“About 15 percent of all women carry a gene with a mutation that could produce a fourth kind of cone pigment. At present we don’t really know if any of them derive an additional dimension of color,” Jacobs said.
However, he said it is difficult for researchers to study color because the way individuals interpret it is highly subjective.
Jacobs agreed with his colleague, saying that though the study shows genetically altered mice are able to distinguish the color red from blue, it is impossible to know exactly what it is like for the mice to experience new colors.
“What we know about color is this: We can very accurately describe it in terms of discrimination ability,” Jacobs said. “On the other hand, the language of color can be inexact. What we really measure with precision is discrimination.”
Andrew MacNamara, a first-year psychology and philosophy major, is colorblind. As proof of the subjective nature of color, he said his understanding of colors differs from that of other people.
“We both call it red because we both recognize [it as such] but we perceive it in different ways. We [could] both call it red, but for me, it could be grey,” MacNamara said.