Researchers at the University of Texas at Houston Medical School have discovered how the brain recognizes the amazing number of colors we see every day.
The finding could one day be used to create a visual prosthesis for those suffering from eye disease or other types of retinal damage.
"The brain uses spatial coding for color," said Daniel Felleman, the lead researcher and professor of neurobiology and anatomy.
Felleman, Yuoping Xiao and Yi Wang studied neuronal activity in macaque monkeys to find that peak activity in certain parts of the brain corresponds to color in the visual world.
Over a period of two-and-a-half years, the team showed seven anesthetized monkeys various colors on a computer screen and measured the amount of blood in various parts of the brain.
"Cells that function alike are grouped together. When they need more oxygen, they can recruit more blood," Felleman explained.
Scientists can measure the reflection of red light to measure hemoglobin, an iron-protein compound found in red blood cells.
Felleman's team was able to examine thousands of neurons at a time. Unlike most studies of brain activity, this one relied on chemical rather than electrical indicators.
The researchers found three different groups of cells in the V2 region of the brain: inner stripes, thick stripes, and thin stripes. Thin stripes appear to have a high proportion of cells interested in color, and are the main source of our color-recognizing abilities.
The V2 area of the brain is identical in macaques and humans, so Felleman suspects the process takes place in people, too.
The stripes themselves contain a map for the ROYGBIV color spectrum -- red, orange, yellow, green, blue, indigo and violet.
"There is a little rainbow of sorts," in the stripes, Felleman said.
There are 17 thin stripes on either side of the brain and six or more rainbows per stripe. Each stripe measures 300 to 500 microns across.
Rick Gilmore, assistant professor of psychology at Penn State, said the discovery of thin stripes is "an important discovery in our overall understanding of color perception."
Felleman's findings solve the puzzle of why the brain groups different wavelengths of light -- or what the brain interprets as color -- together. Gilmore says this study shows that conceptually close objects are also spatially adjacent in the brain.
Felleman said that this is only one map of the spatial representation of color in the brain.
"The brain likes to make maps," Gilmore said. The brain keeps maps for different orientations of line segments, one eye versus another, and different regions of the visual world.
Gilmore says that 2 percent to 5 percent of people in the world inherit color blindness, and that others can suffer damage to the visual cortex as a result of stroke or head injury.
In order to create a practical application for the findings, "we need to understand how the brain functions," he said. One day a camera might be connected to a computer to directly activate the brain and help people overcome visual impairments.
The next step in the study of color perception will be to determine "what cells in V2 are saying to V4," another stop in the brain's visual processing path. This study is "a small step in a long journey to that goal," he added.
Now I want to email that guy...
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