Sadiepete (not a scientist) asked me some questions after having read our recent paper on context and occasion setting in fruit flies ( Drosophila melanogaster). I sat down and answered some of them by email. I think it's a fairly decent description of a few of the key findings, so I decided to post them here as well.

The mushroom-bodies are a brain structure in the brain of most insects. And a prominent one at that which many people in the field know. "Neuropil" in insects are those parts of the brain that do the computing - similar to what people in humans call "white matter". Pretty much. In insects, they are very well separated from each other as well as the rest of the brain (humans: grey matter). This neuropil is called mushroom-bodies, because of the way it looks - they've been discovered over 100 years ago. The MBs are critical for a number of different functions of the brain, but very specifically. In humans, there's a part of the bran that is similarly well-known, the hippocampus (sea-horse). I humans it's involved in memories of faces, places, facts and events as well as in navigation. A famous study shows that London taxi drivers have bigger hippocampi than other Londoners. In flies, we can block the output that the mushroom-bodies provide and see what happens (which is what we did in our experiments).

In the case of learning, 'context' usually refers to the surrounding in which learning takes place. For instance, researchers place rats or mice in a box in which they hear a tone followed immediately by a light electric shock to the feet. Then they place them in a different box but play the same tone and look for the reaction (which should be that the animals freeze). The two boxes are the 'context' in which the tone-footshock learning takes place.
Similarly, the flies do the pattern-heat learning in a color context. So basically what I did was the equivalent of shocking the rats in one box, putting them in the other and then playing the tone without shock. Then Box1: tone-shock, box2, tone-noshock. I did this until the animals learned that box1 means tone-shock and box2 means tone-noshock. In fly terms: "if color1 then pattern means heat. If color2 then pattern means nothing" The colors were "setting the occasion" for when pattern-heat was valid or not. To have flies learn "if-then" was pretty cool: they're only flies after all! What was especially cool was that flies where the MBs had been blocked still could do this, even without such an important part of the brain. This extends and refines our slowly emerging picture of what the MBs do in flies and could help us understand how different brain regions interact in general.