Chocolate Flavonoids Improve Memory In Pond Snails

Lawrence LeBlond for – Your Universe Online

Snails are hardly the creature one might think about when reading about how “superfoods” improve memory. But for University of Calgary researchers, these molluscs were the perfect candidates to study how epicatechin, a flavonoid found in chocolate, affects the memory.

Ken Lukowiak, a researcher at Calgary, was skeptical when undergraduate Lee Fruson first hypothesized about how dietary factors affect memory. “I didn’t think any of this stuff would work,” he recalled.

Despite his skepticism, Lukowiak and Fruson undertook a study on flavonoids, focusing mainly on epicatechin (epi.), and because determining how a single component of chocolate might improve human memory is extremely difficult, Lukowiak decided to use his favorite animal as a subject.

Using the pond snail (Lymnaea stagnalis), Lukowiak and Fruson studied whether the flavonoid from dark chocolate could improve their memories. What they found was remarkable.

According to Lukowiak, the pond snail can be trained to remember a simple activity–to keep their breathing tubes closed when immersed in deoxygenated water. These molluscs usually breathe through their skin, but when oxygen levels drop, they extend their breathing tube above the water to get oxygen. But by gently tapping the tube when they try to open it, the snails can be trained to keep it closed. Lukowiak noted, however, the strength of this memory depends on the type of training regime used.

To determine what worked best for snail memory, Fruson first identified what epi concentration was needed in pond water that would not affect snail behavior. Next, Lukowiak and Fruson tested the snails´ memories. After a half-hour training session in deoxygenated water, the snails were able to form intermediate-term memories (memories lasting less than 3 hours) but not long-term memories (ones lasting 24 hours or more).

The team wondered whether increasing epi levels would improve the snails´ memories, allowing them to form long-term memories after even shorter memory training. Amazingly, the very next day, when the duo plunged the snails into the deoxygenated water, the snails remembered to keep their breathing tubes closed. And after providing two training sessions to the snails, they were able to remember to keep their tubes shut more than 3 days later. The epi had boosted memory and extended the duration of the memory.

But there were still questions, and Lukowiak wondered how strong these epi-memories could be.

He explained that memories can be overwritten by another memory in a process called extinction. However, the original memory is not forgotten and if the additional memory is stored weakly, it can be lost and the original memory restored.

For the next stage of their study, Lukowiak and Fruson tried to extinguish the snails´ epi-boosted memory to determine exactly how strong it was. Having trained the snails to keep their breathing tubes shut, the duo tried to replace it with memory where the snails could open the tubes. However, the snails failed to learn the new memory, and stubbornly kept their tubes shut, indicating the epi-memory was too strong to quench.

Lukowiak suggested that the epi directly affects the neurons that store the memory in the snails, instead of requiring a sensory organ, such as smell, to do the trick. Most predatory animals´ memories are triggered by smell.

The study is published in The Journal of Experimental Biology.

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