The sea slug Aplysia has been a popular model for learning and memory for almost 40 years now. It can perform simple learning tasks and its brain cells (neurons) are so large, they are very easy to experiment on. With the advent of modern genomics technology this simple creature has added another advantage to its arsenal: now you can study the change in gene expression due to learning. At any given time within just a single neuron of Aplysia, more than 10,000 genes are active, according to scientists writing in the December 29, 2006 issue of the journal Cell. The changes in gene activation that occur during and after training the animals will help scientists understand the complex molecular machinery leading to the formation and storage of memories. These finding are important even for the formation of human memories, as the processes known so far are very similar between snails, flies, mice and humans. This new technology will make it possible to train animals and then identify all the genes which have changed their activity due to the learning experience.
ScienceDaily also has a report on the story.
I personally can't wait to exploit these latest developments in our operant conditioning paradigm for Aplysia biting behavior - it will yield a watershed of new insights!