Chocolate makes snails smarter

Ken Lukowiak started off his study, along with Lee Fruson,on the pond snail Lymnaea stagnalis, to find out whether the dark chocolate flavonoid could improve their memories.He concentrated on the flavonoids -- found in a wide range of 'superfoods' including chocolate and green tea, focusing on one particular flavonoid, epicatechin (epi).His team recently published their discovery that epi improves the length and strength of snail memories in The Journal of Experimental Biology.

According to Lukowiak, 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, Fruson identified an epi concentration -- 15 mg m1 pond water -- that didn't affect the snails' behaviour; Then, the duo tested the molluscs' memories.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). 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. 

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.