How brain identifies colour in motion decoded

For football players, being able to quickly judge the jersey colours of teammates and opponents and where they are headed is a valuable skill - and now scientists have found how the brain accomplishes this feat.

Chicago: For football players, being able to quickly judge the jersey colours of teammates and opponents and where they are headed is a valuable skill - and now scientists have found how the brain accomplishes this feat.

A unique population of neurons allows the brain to perceive the combination of colour and motion, scientists say.

University of Chicago researchers have discovered a unique population of neurons that shift in sensitivity toward different colours and directions depending on what is being attended.

"Most of the objects in any given visual scene are not that important, so how does the brain select or attend to important ones?" said study senior author David Freedman at the University of Chicago.

"We've zeroed in on an area of the brain that appears central to this process. It does this in a very flexible way, changing moment by moment depending on what is being looked for," Freedman said.

The visual cortex of the brain possesses multiple, interconnected regions responsible for processing different aspects of the raw visual signal gathered by the eyes.

Basic information on motion and colour are known to route through two such regions, but how the brain combines these streams into something usable for decision-making or other higher-order processes remained unclear.

In the study, Freedman and postdoctoral fellow Guilhem Ibos showed monkeys a rapid series of visual images.

An initial image showed either a group of red dots moving upwards or yellow dots moving downwards, which served as an instruction for which specific colours and directions were relevant during that trial.

The subjects were rewarded when they released a lever when this image later reappeared. Subsequent images were composed of different colours of dots moving in different directions, among which was the initial image.

Researchers looked at neurons in the lateral intraparietal area (LIP), a region highly interconnected with brain areas involved in vision, motor control and cognitive functions.

As subjects performed the task and looked for a specific combination of colour and motion, LIP neurons became highly active.

When the team investigated the responses of LIP neurons, they found that the neurons possessed a unique characteristic.

Individual neurons shifted their sensitivity to colour and direction toward the relevant colour and motion features for that trial.

When the subject looked for red dots moving upwards, for example, a neuron would respond strongly to directions close to upward motion and to colours close to red.

If the task was switched to another colour and direction seconds later, that same neuron would be more responsive to the new combination, researchers found.

The study is published in the journal Neuron. 

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