Abstract
Behavioral responses to many odorants are not fixed but are flexible, varying based on organismal needs. How such variations arise and the role of various neuromodulators in achieving flexible neural-to-behavioral mapping is not fully understood. In this study, we examined how serotonin modulates the neural and behavioral responses to odorants in locusts (Schistocerca americana). Our results indicated that serotonin can increase or decrease appetitive behavior in an odor-specific manner. On the other hand, in the antennal lobe, serotonergic modulation enhanced odor-evoked response strength but left the temporal features or the combinatorial response profiles unperturbed. This result suggests that serotonin allows for sensitive and robust recognition of odorants. Nevertheless, the uniform neural response amplification appeared to be at odds with the observed stimulus-specific behavioral modulation. We show that a simple linear model with neural ensembles segregated based on behavioral relevance is sufficient to explain the serotonin-mediated flexible mapping between neural and behavioral responses.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
The previous version of the manuscript was reviewed at eLife and has been revised to provide additional details on our electrophysiology and behavioral protocols, include additional current injection experiments to clarify excitability changes in individual neurons, and include control data to show responses to the solvent in which odorants were diluted. Finally, some claims regarding the role of serotonin on hunger-state dependent olfactory modulation has also been toned down or clarified.
