Where do our brains process colors?

A new study identifies the neural networks that process light, particularly the areas of the brain that encode the colors we see.

Scientific research has long shown that such colors are not inherent to the physical world, but rather a result of how our brains process light.

“We’ve been able to show where it happens in the visual pathway, which is relatively early,” says Steven Shevell, a professor of psychology, ophthalmology, and visual science who directs the Institute for Mind and Biology at the University of Chicago.

“It’s like a road map that shows where to look for the neural circuits that cause the transition from the earliest neural representations of the physical world to our mental world.”

Using brain scans and a novel “switch-rivalry” technique, he and his coauthors discovered that the primary visual cortex, which is the first stage of cortical visual processing, does not accurately represent colors we experience. On the other hand, higher areas in the visual pathway follow the hues we actually see.

Building on previous work from Shevell’s lab, the researchers conducted their experiments with a technique that rapidly switched back and forth between two different wavelengths of light. Although the change happened six times per second, viewers saw one sustained color (green) for several seconds before their perceived color shifted to another color (magenta).

Upon reviewing fMRI scans, the researchers found that the activity in higher visual cortex areas were the ones that matched the colors study subjects saw. Those results mark an important step in explaining the transition from encoding physical light entering our eyes to the perceptual experience of seeing color.

Shevell had previously published about the use of switch rivalry in a 2017 paper. That work revealed a similar color perception phenomenon, but did not identify which areas of the brain were responsible.

Now, Shevell hopes these new findings can lead to research that clarifies how the different regions of the visual pathway accomplish the transition to human color perception.

“We can zero in and do experiments in those areas to understand how this happens,” he says. “We weren’t able to show how transitions happen. We showed that they did happen. We want to understand how it is done.”

The research appears in Proceedings of the National Academy of Sciences. Additional researchers from the University of Chicago, Sungkyunkwan University, and Florida Atlantic University contributed to the work.

Source: University of Chicago

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