They may not have many life-changing decisions to make, but when they are faced with a choice, freshwater mollusks are incredibly efficient at making up their minds, using just two types of brain cell to reach their verdict. Describing this discovery in the journal Nature Communications, researchers from the University of Sussex explain how this incredible resoluteness enables the snails to save brain energy when going about their business.
While some humans may expend infuriating amounts of energy just deciding what to wear in the morning, mollusks belonging to the Lymnaea family are admirably single-minded, and direct most of their brain power towards locating food. By measuring the electrical charges – or action potentials – given off by specific types of neurons in the snails’ brains when seeking out grub, the study authors found that the animals’ activity was controlled by just two varieties of nerve cell.
One of these neurons – known as vTN – encodes sensory information regarding whether or not food is present in the snails’ immediate environment, while the second type, called N3t, tells the snail whether or not it is hungry enough to eat this food. In this sense, it’s a bit like snail Tinder, as all decisions are based on nothing more than the proximity and attractiveness of a piece of food.
When hungry, Lymnaea seek out sustenance by “biting” the air in order to test out whether food is present. If they happen to sink their teeth into something edible, they then perform what the researchers call “consummatory bites,” which are accompanied by a swallowing action as they devour their food.
Lymnaea are able to save energy by using the fewest possible types of neuron necessary to make a decision. vitstudio/Shutterstock
The study authors discovered that when the snails were full, their N3t neurons began to fire at a higher rate, causing them to stop their exploratory air biting. In contrast, when they were deprived of food for several days, these neurons fired at a lower rate, causing the snails to perform more of these “appetitive bites.”
Upon finding food, the snails’ vTN neurons became active, essentially “swiping right” and initiating the switch to consummatory biting. The swallowing action that accompanies this food gobbling is then coordinated by a wider range of neurons, which suddenly spring into action, using up a considerable amount of energy.
Based on this discovery, the study authors conclude that this system helps the snails to save on brain power, by ensuring that the neurons involved in swallowing do not become active unless absolutely necessary, and with the guarantee that food is present, thereby making it worthwhile.
In a statement, lead researcher George Kemenes explained how the study “reveals for the first-time how just two neurons can create a mechanism in an animal's brain which drives and optimizes complex decision-making tasks.” Taking this one step further, he stated that “this will eventually help us design the 'brains' of robots based on the principle of using the fewest possible components necessary to perform complex tasks.”
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