A Calculus Affair

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Roundworms seem to be indulging in some serious mathematical calculations in their hunt for food, find scientists.

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In their search for food, tiny roundworms — no larger than a few centimetres — appear to be engaging in a bit of senior school mathematics. A team of US-based researchers has found that two distinct cells in the brains of roundworms make up a specialised, miniature computer that guides the worm’s food-finding behaviour through functions that mimic calculus.

Biologist Shawn Lockery at the University of Oregon and his colleagues have shown how the two cells work in tandem to guide a worm towards food. The researchers believe that the computational mechanism that occurs in the roundworm’s brain is similar to what drives a person to the aroma of a meal in the making in the kitchen. Their findings appeared last week in the journal Nature.

“We’ve discovered a tiny, specialised computer inside the primitive roundworm,” said Lockery. “The computer calculates the rate of change of the strengths or concentrations of various tastes.” The analysis of the rate of change is done by a process called differentiation — a key element of calculus, a mathematical discipline typically introduced in senior school.

“The worm uses this information to find food and avoid poisons,” said Lockery, who had first predicted the existence of such a mechanism in the roundworm brain in 1999 after observing how the worms change directions based on taste and smell.

The two neurons make up the antagonistic sensory cues (ASE) system, and function just as two nostrils or two eyes. The left neuron controls an on switch, while the right neuron controls an off switch.

In their experiments, the researchers exposed the roundworms to salt and pepper. They showed that the left neuron is active when the worms move forward, and the right neuron is active when the worms begin a turn or searching motion.

The scientists reasoned that artificial activation of the left neuron ought to make the worms move straight ahead, while activation of the right neuron would make them turn to find something, or avoid something. That’s exactly what their experiments with pepper have revealed. Which way a roundworm turns will depend on which neuron has been turned on.

Researchers believe the finding could help research aimed at the treatment of people who have problems involving smell or taste. But that’s a long-term goal. For now, it’s just an insight into how even roundworms do some calculus.

Sources: The Telegraph (Kolkata, India)

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