Only hungry flies learn odor-sugar association

Drosophila melanogaster flies were shown to learn to associate odor with sugar presentation. The performance during the test was shown to be dependent on the statiation state of the animal (krashes et al. 2009). The dependency of satiation during training has been postulated from different experiments. However, the difference in motivation during the test could have explained these results. I performed an experiment to tackle this question directly, using the conditioning paradigm published earlier (Colomb et al. 2009). Flies were starved (or not) before training. After training, they were put on food to cancel the difference in satiation state between the two groups, before beeing starved again before the test. Flies sated during training show no memory at all, while control flies show normal memory retention scores two days after training. Colomb J, Kaiser L, Chabaud M-A, Preat T (2009) Parametric and genetic analysis of Drosophila appetitive long-term memory and sugar motivation. Genes, brain, and behavior 8: 407–15. doi:10.1111/j.1601-183X.2009.00482.x Krashes MJ, DasGupta S, Vreede A, White B, Armstrong JD, et al. (2009) A neural circuit mechanism integrating motivational state with memory expression in Drosophila. Cell 139: 416–27. doi:10.1016/j.cell.2009.08.035