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Worm's search for food involves complex mathematics

By Brooks Hays
Worm's search for food involves complex mathematics
Scientists described the mathematics behind the roundworm's search for food. Photo by Alon Zaslaver/Hebrew University

Aug. 2 (UPI) -- Scientists have revealed the complex math behind the nematode's search for food.

Like most worms, roundworms, Caenorhabditis elegans, rely on their sense of smell to track down food. But how do worms interpret smells? How is a scent translated in the worm's brain?

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Researchers suggests the worm and it's brain play a game of "hot and cold."

"Imagine you're in a huge dark house and a chocolate cake has just been taken out of the oven," Alon Zaslaver, neurogeneticist at the Hebrew University of Jerusalem, said in a news release. "To find the cake, you'll probably sniff around to see what direction the cake scent is coming from and begin walking in that direction."

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The worm takes a similar approach. When a neural cell receives a scent, the brain tells the nematode to start crawling. As long as the scent grows in strength, the worm will keep going in the same direction. If the scent begins to dissipate, the worm will stop and reconsider.

In the newest study, scientists set out to understand how exactly the roundworm formulates an alternative route.

Their analysis -- detailed in the journal Nature -- revealed the action of a secondary neural cell. The first cell is tasked with tracking the trajectory of the scent received by the first cell. The second cell determines whether the scent's intensity is positive or negative. It it's negative -- getting weaker -- the second cell tells the worm to stop and take different path.

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The two cells work in tandem to direct the worm toward the original scent.

Scientists tagged the worm's neurons with a fluorescent protein and imaged its brain as the nematode searched for food in the lab. Scientists withheld food from the test subjects before letting them loose in a tank with specifically positioned stimuli.

Based on the two the worms response to the stimuli gradients, scientists formulated mathematical systems to describe the worm's search for food.

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"These worms teach us an important lesson," Zaslaver.

Though the worm's approach seems simple, it's commitment to trial and error -- to troubleshooting -- makes the strategy foolproof.

"We need a backup system in place that monitors whether we are indeed moving in the 'right' direction," he said, "even if that new path differs from the one we originally set out on."

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