New research has found that fruit flies’ eyes are easily fooled by static visual patterns where there is no movement.
For an invertebrate with compound eyes (which, close up, look at themselves like an optical illusion), this is a notable similarity, and it still exists after millions of years of distinct development.
Neuroscientist Damon Clarke of Yale University says, “The last common ancestor of flies and humans lived half a billion years ago, but the two species have developed similar strategies to gain momentum.”
“Understanding these shared strategies can help us fully understand the human visual system.”
Combining behavioral measurements, genetic silence and neural imaging, the team concludes that fruit flies (Drosophila melanogaster), Like vertebrates, experience confusion in static images because they capture the same basic brain circuitry as ours – ours is simply more complex.
Traditionally, it was thought that fly eyes and human eyes have evolved quite differently in development, but recent genetic research has found the same underlying genetic basis for the eye in all animal phyla.
Subsequently, some scientists have argued that there was only one original eye, which then split into various forms over millions and millions of years.
And the similarities are still clear to see. Previous research on optical illusion has shown non-human primates, cats, and fish, where all can be tricked into seeing motion. But it has never been shown on a creature because it develops away from us as a fruit fly.
Which is a shame, because fruit flies have small brains that allow scientists to closely examine the activity of neurons.
“It was exciting to find that flies experience motion in static images the same way we do,” says Clark.
Mostly because it gave us a glimpse at what is going on in our minds. Nobody is really sure what it is about those optical illusions that overwhelm the most appropriate parts of our brain.
Some evidence suggests that we see motion in these stationary pictures because photos typically have a high contrast, which makes our brains process faster, presenting data to the brain in an order that would cause an illusion of motion. (Black → Dark Gray → White → Light Gray → Black).
Other evidence shows the effect of small, involuntary jerks when they are examining something. Both may very well be true at the same time.
Because we already know a lot Drosophila Brains, the researchers were able to place fruit flies for testing, and then used neural imaging to interpret the results.
When flying near a stationary image with the speed of illusion, like below, fruit flies turn to the photograph, which indicates that they were watching a continuous movement.
Motion in the fruit fly brain is first detected by direction-selective neurons T4 and T5, and they react to sharp contrast edges.
When the authors eliminated these initial motion detector neurons, the illusion of motion disappeared.
Further neural imaging revealed that T4 and T5 were working in opposite directions. By closing only one of these neurons, the authors had the fruit flies bend in the opposite direction to what they would have done if both neurons were active.
This suggests that there is a small imbalance between these motion detectors and what flies do or do not respond to stimulation.
“When we adapted human observers to move light edges or dark edges,” the author explains, “we can also add the magnitude and direction of their perceptions, suggesting that fly-like mechanisms also exist in humans. Can reduce this confusion. ”
Therefore, they argue, there is something in the architecture of our brain that is driving this illusion of motion, and can help explain that in high-contrast and subtle movements of the eye in certain directions, as well as confusion. Why have they become criminals?
The study was published in PNAS.