Figure 1.

Training and testing of an aversive olfactory association in Drosophila. Flies are trained and tested in a “teaching machine,”7 consisting of an upper training chamber and a lower testing chamber. Training consists of two steps. During the first step, flies are exposed simultaneously to an odor (odor A, shown in purple), and electrical shocks (yellow). At step 2, flies are exposed to a second odor (odor B, green), in the absence of shocks. Flies learn to associate odor A, but not odor B, with aversive shocks. Learning and memory of this association can be measured at various time points after training by testing flies by placing them at the choice point between odors A and B, and allowing them to choose between these odors. Memory‐associated behaviors can be quantified as a performance index, calculated by subtracting the percentage of flies choosing the shock‐paired odor from the percentage of flies choosing the unpaired odor. Appetitive associations can be measured in a similar fashion in starved flies, by replacing electrical shocks with sucrose rewards