Brain may 'see' more than the eyes, study indicates

November 1, 2012 by Fariss Samarrai
The simple eyes of fruit fly larvae provide just enough visual input to allow the animal’s brain to assemble images.

(Medical Xpress)—Vision may be less important to "seeing" than is the brain's ability to process points of light into complex images, according to a new study of the fruit fly visual system currently published in the online journal Nature Communications.

University of Virginia researchers have found that the very simple eyes of fruit fly larvae, with only 24 total photoreceptors (the contains more than 125 million), provide just enough light or to allow the animal's relatively large brain to assemble that input into images.

"It blows open how we think about vision," said Barry Condron, a in U.Va.'s College of Arts & Sciences, who oversaw the study. "This tells us that visual input may not be as important to sight as the brain working behind it. In this case, the brain apparently is able to compensate for the minimal visual input."

Condron's graduate students, Elizabeth Daubert, Nick Macedonia and Catherine Hamilton, conducted a series of experiments to test the vision of fruit fly larvae after they noticed an interesting behavior of the animals during a different study of the nervous system. They found that when a larva was tethered to the bottom of a petri dish, other larvae were attracted to it as it wiggled attempting to free itself.

The animals apparently saw the writhing motion and were attracted to it, willingly traveling toward it. After several further experiments to understand how they sensed the motion, the researchers learned that the nearly blind animals were seeing the action, by wagging their heads side-to-side in a scanning motion to detect it, rather than by only hearing it or feeling vibration or by smelling the trapped larva. This was a surprise because of the very simple and limited vision of fruit fly larvae.

"The answer must be in the large, somewhat sophisticated brain of these animals," Condron said. "They are able to take just a couple dozen points of light and then process that into recognizable images; something like when an astronomer with a small telescope is able to use techniques to refine a limited image into useful information about a star."

Condron believes the animals are able to assemble useful images by rapidly scanning their heads and, in so doing, gather up enough light points to allow the brain to compose a panoramic image clear enough to "see."

The researchers tested this by presenting larva with a video of a writhing larva (therefore no vibration, no sound and no smell) and found that the larvae still detected and sought out the struggling larva on the video. They also learned that if they slowed down or sped up the video, the larvae were less attracted or not attracted at all to the video larva. They also were not attracted to dead real larva, or to tethered larva of another species, and they also had difficulty finding tethered larva in near darkness.

"Apparently they are – to a very high degree – visually sensitive to detail and rate of motion and can recognize their own species in this way," Condron said. "This provides us with a good model for trying to understand the role that the brain plays in helping organisms, including humans, to process images, such as recognizing faces."

He noted that the head scanning apparently plays an important role in helping the larvae to bring together multiple visual inputs into a unified whole for the brain to process, similar to collecting together multiple pixels to form a picture. Condron said people with severe vision loss also tend to use head scanning as a means for collecting a "picture" from very dim light sources. Likewise, visually impaired people who have received experimental retinal implants of just a small number of pixels also often scan their heads to take in enough light to form mental images.

"It's easy for lab biologists to view as simple animals that just feed and reproduce, but we are beginning to realize that that may be in contradiction to the big brain," Condron said. "There's more to what they are able to do than previously thought, whether using that for behaviors or for constructing images from a limited visual system."

He said the fruit fly serves as an excellent model for studying neurons because the animal has only about 20,000 of them, whereas humans have about 100 billion. Yet there are many similarities to how fruit fly and human neurons work. According to Condron, researchers are within a year of mapping the entire nervous system of the fruit fly, which then will pave the way for greater understanding of how neurons work in a range of organisms, including humans.

Related Stories

Recommended for you

How the brain's wiring leads to cognitive control

October 6, 2015

How does the brain determine which direction to let its thoughts fly? Looking for the mechanisms behind cognitive control of thought, researchers at the University of Pennsylvania, University of California and United States ...

What role does the hippocampus play in memory?

October 6, 2015

(Medical Xpress)—Meet the hippocampus: A seahorse-shaped structure in the cerebral cortex's medial temporal lobe, it's part of the limbic system, generally believed to be involved in spatial navigation and establishing ...

Runner's high linked to cannabinoid receptors in mice

October 6, 2015

(Medical Xpress)—A team of researchers from several institutions in Germany has found a link between cannabinoid receptors in mice and what is commonly known as "runner's high." In their paper published in Proceedings of ...


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Nov 02, 2012
The researchers tested this by presenting larva with a video of a writhing larva (therefore no vibration, no sound and no smell)...

If you are called a bird brain just remember that's a step up from the fruit fly's brain.

1 / 5 (3) Nov 02, 2012
The problem is that most "scientists" have never picked up a copy of Leibniz' Monadology, leaving it to a musty corner of the history of philosophy. But the fact is Leibniz presaged all this (and much more)with his model of lesser (biological) monads each having a window on the world! The problem is that most "scientists" have never picked up a copy of Leibniz' Monadology, leaving it to a musty corner of the history of philosophy. But the fact is Leibniz presaged all this (and much more)with his model of lesser (biological) monads each having a window on the world! http://thingumbob...=leibniz

1 / 5 (1) Nov 02, 2012
I thought we already knew that 'seeing' is a construct of the brain. Take the lack of blue cones for example, yet we still 'see' blue as well as other colours.
not rated yet Nov 02, 2012

Let "scientists" indulge in Panpsychismus first.

The bicycle first.(Panpsychhimus)
The car second. (Monadologie)
Without maturity your feet don't touch the pedals of the car.
You can't see over the steering wheel.
You experience the distance traveled on a bike with little risk of overseeing/overlooking the objects along the way.

Cone etiology is 'adaptive' to the atmospheric composition existing on planets besides earth.
(If you conjecture the basis of life on earth can exist elsewhere)
not rated yet Nov 04, 2012
You need to revise your knowledge: http://en.wikiped...r_vision

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.