@article {49013,
	title = {Repetitive aggressive encounters generate a long-lasting internal state in Drosophila melanogaster males.},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {115},
	year = {2018},
	month = {2018 Jan 16},
	pages = {1099-104},
	abstract = {<p>Multiple studies have investigated the mechanisms of aggressive behavior in Drosophila; however, little is known about the effects of chronic fighting experience. Here, we investigated if repeated fighting encounters would induce an internal state that could affect the expression of subsequent behavior. We trained wild-type males to become winners or losers by repeatedly pairing them with hypoaggressive or hyperaggressive opponents, respectively. As described previously, we observed that chronic losers tend to lose subsequent fights, while chronic winners tend to win them. Olfactory conditioning experiments showed that winning is perceived as rewarding, while losing is perceived as aversive. Moreover, the effect of chronic fighting experience generalized to other behaviors, such as gap-crossing and courtship. We propose that in response to repeatedly winning or losing aggressive encounters, male flies form an internal state that displays persistence and generalization; fight outcomes can also have positive or negative valence. Furthermore, we show that the activities of the PPL1-γ1pedc dopaminergic neuron and the MBON-γ1pedc\&gt;α/β mushroom body output neuron are required for aversion to an olfactory cue associated with losing fights.</p>
},
	issn = {1091-6490},
	doi = {10.1073/pnas.1716612115},
	author = {Kim, Yong-Kyu and Saver, Mathias and Simon, Jasper and Kent, Clement F and Shao, Lisha and Eddison, Mark and Agrawal, Pavan and Texada, Michael and Truman, James W and Heberlein, Ulrike}
}
@article {48786,
	title = {Dissection of the Drosophila neuropeptide F circuit using a high-throughput two-choice assay.},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {114},
	year = {2017},
	month = {2017 Sep 05},
	pages = {e8091-9},
	abstract = {<p>In their classic experiments, Olds and Milner showed that rats learn to lever press to receive an electric stimulus in specific brain regions. This led to the identification of mammalian reward centers. Our interest in defining the neuronal substrates of reward perception in the fruit fly Drosophila melanogaster prompted us to develop a simpler experimental approach wherein flies could implement behavior that induces self-stimulation of specific neurons in their brains. The high-throughput assay employs optogenetic activation of neurons when the fly occupies a specific area of a behavioral chamber, and the flies{\textquoteright} preferential occupation of this area reflects their choosing to experience optogenetic stimulation. Flies in which neuropeptide F (NPF) neurons are activated display preference for the illuminated side of the chamber. We show that optogenetic activation of NPF neuron is rewarding in olfactory conditioning experiments and that the preference for NPF neuron activation is dependent on NPF signaling. Finally, we identify a small subset of NPF-expressing neurons located in the dorsomedial posterior brain that are sufficient to elicit preference in our assay. This assay provides the means for carrying out unbiased screens to map reward neurons in flies.</p>
},
	issn = {1091-6490},
	doi = {10.1073/pnas.1710552114},
	author = {Shao, Lisha and Saver, Mathias and Chung, Phuong and Ren, Qingzhong and Lee, Tzumin and Kent, Clement F and Heberlein, Ulrike}
}
