Since this will be a main focus of my master thesis I started a literature analysis to check how the idea of a possible “reward system” in Drosophila is addressed. Based on how authors address this topic, I categorized the results by either “differentiated” or “undifferentiated”. In this case undifferentiated means the authors were addressed certain sets of neurons as “reward neurons” or “punishment neurons”, although they could never be classified in this broad sense. For example a lot of papers of the “undifferentiated” category address dopaminergic neurons from the PAM cluster as “reward” neurons, since flies formed appetitive olfactory associative memories, when the CS (odors) were paired with optogenetic activation these neurons. Since PAM neurons are activated during sugar detection it makes sense that they can substitute for reward, but that doesn’t make them “reward neurons”. Real “reward neurons” would activated in any instance of reward, independent of whether it is sugar, mating or water. Many authors do not address this issue properly. Although this analysis is not finished yet I created two plots to visualize the general trends: