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

黑腹果蝇（Drosophila melanogaster）已被证实可习得气味与糖类投喂建立的关联。其测试阶段的行为表现依赖于个体的饱足状态（Krashes等，2009）。已有多项实验推测训练阶段的饱足状态会影响实验结果，但测试阶段的动机差异或可解释上述观测现象。

本研究采用此前发表的条件化实验范式（Colomb等，2009），直接针对该问题开展实验。具体实验流程为：果蝇在训练前被施以饥饿处理（或不作处理）；训练结束后，将所有果蝇置于食物中以消除两组间的饱足状态差异，随后在测试前再次对其进行饥饿处理。实验结果显示，训练期间处于饱足状态的果蝇未表现出任何记忆，而对照组果蝇在训练两天后仍可检测到正常的记忆保持得分。

参考文献：
1. Colomb J, Kaiser L, Chabaud M-A, Preat T (2009) 黑腹果蝇奖赏性长时记忆与糖类动机的参数与遗传分析. 《基因、大脑与行为》8: 407–15. doi:10.1111/j.1601-183X.2009.00482.x
2. Krashes MJ, DasGupta S, Vreede A, White B, Armstrong JD, 等 (2009) 整合动机状态与果蝇记忆表达的神经环路机制. 《细胞》139: 416–27. doi:10.1016/j.cell.2009.08.035