Epicatechin (epi), a flavonoid found in chocolates, improves length and strength of molluscan memories, states study.
According to Ken Lukowiak from the University of Calgary, the molluscs can be trained to remember a simple activity - to keep their breathing tubes closed when immersed in deoxygenated water.
He explains that pond snails usually breathe through their skins, but when oxygen levels fall, they extend the breathing tube above the surface to supplement the oxygen supply.
However, the snails can be trained to remember to keep the breathing tube closed in deoxygenated water by gently tapping it when they try to open it, and the strength of the memory depends on the training regime.
First, University of Calgary undergraduate Lee Fruson identified an epi concentration - 15 mg m1 pond water - that didn't affect the snails' behaviour.
Then, the duo tested the molluscs' memories. Explaining that a half-hour training session in deoxygenated water allows the snails to form intermediate-term memories (lasting less than 3 h) but not long-term memories (lasting 24 h or more), Fruson and Lukowiak wondered whether epi would improve the snail's memories, allowing them to form long-term memories after shorter memory training.
Amazingly, when Fruson plunged the molluscs into deoxygenated water to tested their memories a day later, they remembered to keep their breathing tubes closed. And when the duo provided the snails with two training sessions, the animals were able to remember to keep their breathing tubes shut more than 3 days later.
Epi had boosted the molluscs' memories and extended the duration, but how strong were the epi-memories?
Lukowiak explains 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.
So, Fruson and Lukowiak decided to find out how strong the epi-boosted memory was by trying to extinguish it. Having trained the snails, the duo then tried to replace it with a memory where the snails could open their breathing tubes.
However, instead of learning the new memory, the epi-trained snails stubbornly kept their breathing tubes shut. The epi-memory was too strong to be extinguished.
The duo also found that instead of requiring a sensory organ to consolidate the snails' memories - like their memories of predators triggered by smell - epi directly affects the neurons that store the memory.
The study has been published in The Journal of Experimental Biology.