Owl eyes are round, but not spherical. These immobile, tubular structures sit on the front of an owl’s face like a pair of built-in binoculars. They allow the birds to focus in on prey and see in three dimensions, kind of like humans — except we don’t have to turn our whole heads to spot a slice of pizza beside us.
Although owls and humans both have binocular vision, it has been unclear whether these birds of prey process information they collect from their environments like humans, because their brains aren’t as complex. But in a study published in the Journal of Neuroscience on Monday, scientists tested the ability of barn owls to find a moving target among various shifting backgrounds, a visual processing task earlier tested only in primates.
The research suggests that barn owls, with far simpler brains than humans and other primates, also group together different elements as they move in the same direction,to make sense of the world around them.
“Humans are not so different from birds as you may think,” said Yoram Gutfreund, a neuroscientist at Technion Israel Institute of Technology who led the study with colleagues from his university and RWTH Aachen University in Germany.
A critical part of perception is being able to distinguish an object from its background. One way humans do this is by grouping elements of a scene together to perceive each part as a whole. In some cases, that means combining objects that move similarly, like birds flying in a flock, or the single bird that breaks away from it.
Scientists have generally considered this type of visual processing as a higher level task that requires complex brain structures. As such, they’ve only studied it in humans and primates.
But Dr. Gutfreund and his team believed this ability was more basic — like seeing past camouflage. A barn owl, for example, might have evolved a similar mechanism to detect a mouse moving in a meadow as wind blows the grass in the same direction.
To test visual detection tactics in their feathered subjects, they showed barn owls screens of black, moving dots on a gray background and attached cameras to their heads to track their gazes. Then the team measured how long it took the birds to turn their heads toward a target dot, moving in a different direction than numerous other shifting dots.
The owls were able to spot the target. They were better at finding it when the contrasting dot direction was uniform rather than scattered. Even though the elements were all black dots, the direction they were moving made a big difference in the owl’s perception of the world — and how its brain responded.
The researchers also recorded activity from the ocular tectum, a brain area involved in basic visual processing in owls and many other vertebrates. They found that it activated more or less depending on the movement of the dots, suggesting it was responsible for performing this seemingly complex task.
“What we find is considered higher level processing in an area that is not traditionally considered a higher level area,” Dr. Gutfreund said. He thinks this ability was conserved through evolution in a similar part of the human brain called the superior colliculus, which helps direct attention among other functions.
But how the ability evolved, or how it may play out differently in birds and mammals is still a mystery, Dr. Gutfreund said. For now, they want to determine the path traveled through the owl’s brain by these movement-grouping signals.
“It’s not so easy to do these experiments,” said Dr. Gutfreund, but he believes this motion grouping ability is widespread in the animal kingdom. “I think that the visual system basically evolved to identify targets for behavior. This is why we have the brain.”
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