The environmental stress conditions that help pond snails to remember and those which make them forget have been identified by Canadian scientists.
The find could help scientists understand how memory works in humans.
When the snails (Lymnaea stagnalis) were overcrowded or exposed to water with low calcium, which they need to grow their shells, their ability to form LTM (long term memory) was greatly reduced.
However, predatory scents reverse these effects, and even overpower the effect of crowding and low-calcium.
"Being able to remember which foods made them sick and which foods were alright will increase their probability of finding suitable food in the future," explained Dr Sarah Dalesman.
In the current study, the scientists 'trained' encouraged the snails to come up to the surface to breathe by artificially reducing the oxygen in the water.
When the snail opened its pneumostome at the surface, it was given a gentle poke with a wooden stick, causing it to close again.
After a repetition of 2 hours, the snail seemed to remember and reduced the number of times it came up for air a day later, showing long term memory.
They have large neurons, which allow them to pinpoint exactly where in the brain memory is formed.
The on going study aims to develop an understanding of how stressors interact in Lymnaea stagnalis and to shed light on the effect of stress on memory formation in higher animals, including humans.