Studying the kinetics of operant learning in Drosophila using the OptoPAD/FlyPAD system – The connection between motivational states and social conditions

Operant learning is a behavior “controlled” by its consequences. In practice, the behavioral phenotype is modified by reinforcement or punishment.

Neuropeptide F (NPF) neurons are related to the reward system in Drosophila. High transcript levels of NPF were found in satiated male Drosophila brain post feeding, sex, and other necessary actions related to and essential for survival. In addition, it has been proved that activation of NPF neurons is pleasurable and rewarding to the fly.

The FlyPAD / OptoPAD is a high-throughput system enabling the study of choice behavior of individual flies, with the additional ability to operantly activate specific neurons using optogenetics. We applied this system to characterize the kinetics of operant learning of male and female flies which were exposed to either socialization or isolation.

We hypothesize that specific social experiences create motivation for reward, resulting in different kinetics of operant learning. Our results show that group-housed males preferred sipping from the illuminating well, self-activating NPF neurons, while isolated males hadn’t shown this preference. In addition, using this operant assay, we noticed a faster learning curve in females compared to males.

We suggest that our experimental paradigm can be used to strengthen the link between neuronal circuitry involved in the reward system and operant behavioral phenotypes, and its modulation by prior social experience.