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| Just what we need - smarter snails |
From
Science Daily
Type
the word 'superfood,' into a web browser and you'll be overwhelmed: some
websites even maintain that dark chocolate can have beneficial effects. But
take a closer look at the science underpinning these claims, and you'll
discover just how sparse it is.
So, when University of Calgary undergraduate
Lee Fruson became curious about how dietary factors might affect memory, Ken
Lukowiak was sceptical. 'I didn't think any of this stuff would work', Lukowiak
recalls.
Despite
his misgivings, Lukowiak and Fruson decided to concentrate on a group of
compounds -- the flavonoids -- found in a wide range of 'superfoods' including
chocolate and green tea, focusing on one particular flavonoid, epicatechin
(epi).
However,
figuring out how a single component of chocolate might improve human memory is
almost impossible -- too many external factors influence memory formation -- so
Lukowiak turned to his favourite animal, the pond snail Lymnaea
stagnalis, to find out whether the dark chocolate flavonoid could improve
their memories.
They
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 (pneumostomes) 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; 'We have to be sure that we're not looking at
wired animals', chuckles Lukowiak. 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. So, Lukowiak is keen to
look directly at the effect that epi has on memory neurons and adds that the
cognitive effects of half a bar of dark chocolate could even help your grades:
good news for chocoholics the world over.
Story Source:
The
above story is reprinted from materials provided by The
Journal of Experimental Biology, via EurekAlert!, a service of AAAS. The original article was
written by Kathryn Knight.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
1. Lee Fruson, Sarah Dalesman and Ken
Lukowiak. A flavonol present in cocoa [(−)epicatechin] enhances snail
memory. The Journal of Experimental Biology, 2012 DOI: 10.1242/jeb.070300