A tiny ball functions like a treadmill for this fly, which turns in response to moving images. (Credit: Stanford University)

Flies sense motion the same way we do

After putting flies on tiny spherical treadmills, scientists found that humans and flies share a similar strategy to view moving objects.

“What’s really exciting to me is that no one would have expected this deep similarity between two animals that are so evolutionarily different,” says Thomas Clandinin, an associate professor of neurobiology at Stanford University and one of the authors of the study, which was published this month in the journal Nature Neuroscience.

The last common ancestor of flies and humans lived more than 500 million years ago when the planet looked quite different. Nonetheless, repeated patterns in the natural environment led ancestors of both organisms to evolve similar strategies to sense movement.

How the brain evolves

It is likely this model evolved twice–once in a human ancestor and once for a fly ancestor–because flies and humans are so far apart on the evolutionary tree, according to neurobiologist Damon Clark, a lead author of the paper.

Despite the fact that the brains of humans and flies are quite different, they analyze motion in similar ways. Clark, now a professor at Yale University, was a Stanford postdoctoral researcher in Clandinin’s group when he worked on the project.

Scientists know quite a bit about how the eye detects light. However, they don’t completely understand how the brain translates a series of chemical signals into an image. The research team examined motion perception in flies and humans to learn more about the visual system and the brain’s problem-solving strategies.

“The big question is really ‘How does the brain evolve?'” says Anthony Norcia, an author of the paper and a Stanford professor of psychology.

The study suggests there may be an optimal way to view natural moving objects that share fundamental properties, Clark says. By statistically modeling these properties, theoretical neuroscientist James Fitzgerald, also a lead author of the paper, was able to develop a framework to test these theories.

Speed, direction, brightness

Both humans and flies discern three types of information about a moving object: its speed, direction of motion, and brightness. Previous models were flawed because they discarded information about brightness, Norcia says.

The team tested its theories in both humans and flies.

In Norcia’s lab, volunteers watched videos while researchers monitored their scalp electroencephalogram (EEG) signals. They also answered questions about their perception of motion based on the videos.

But to test flies, researchers couldn’t just ask them which way an image was moving. Instead, Clark says, they capitalized on a known fly trait: flies turn in the direction of motion.

Clark tethered flies to sticks, posed them on tiny spherical treadmills, and then screened videos while monitoring their movements.

Fitzgerald, who was previously a graduate student at Stanford and is now a postdoctoral fellow at Harvard University, says he chose to study motion in flies because it could be possible to pinpoint the neural networks involved.

“The ultimate hope is by finding an example of how flies solve this particular problem, it could give us some insight into how the brain solves problems more generally,” Fitzgerald says.

Source: Stanford University

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  1. Babu G. Ranganathan

    NOT MADE BY NATURE! Just because something exists in nature doesn’t mean it was invented or made by Nature. If all the chemicals necessary to make a cell were left to themselves, “Mother Nature” would have no ability to organize them into a cell. It requires an already existing cell to bring about another cell. The cell exists and reproduces in nature but Nature didn’t invent or design it! Nature didn’t originate the cell or any form of life. An intelligent power outside of nature had to be responsible.

    Natural laws can explain how an airplane or living cell works, but it’s irrational to believe that mere undirected natural laws can bring about the origin of an airplane or a cell. Once you have a complete and living cell then the genetic program and biological machinery exist to direct the formation of more cells, but how could the cell have originated naturally when no directing code and mechanisms existed in nature? All of the founders of modern science believed in God. Read my Internet article: HOW FORENSIC SCIENCE REFUTES ATHEISM

    Only evolution within “kinds” is genetically possible (i.e. varieties of dogs, cats, etc.), but not evolution across “kinds” (i.e. from sea sponge to human). How did species survive if their vital tissues, organs, reproductive systems were still evolving? Survival of the fittest would actually have prevented evolution across kinds! Read my Internet article: WAR AMONG EVOLUTIONISTS! (2nd Edition). I discuss: Punctuated Equilibria, “Junk DNA,” genetics, mutations, natural selection, fossils, genetic and biological similarities between species.

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    Babu G. Ranganathan*
    (B.A. theology/biology)

    Author of popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

    * I have had the privilege of being recognized in the 24th edition of Marquis “Who’s Who In The East” for my writings on religion and science, and I have given successful lectures (with question and answer time afterwards) defending creation from science before evolutionist science faculty and students at various colleges and universities

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