The neurobiological basis of personality in flies. Benjamin L. de Bivort^1,2,3, Jamey S. Kain¹, Sean M. Buchanan¹, Julien Ayroles³, Chelsea Jenney¹, Sarah Zhang¹. 1) Rowland Institute, Harvard University, Cambridge, MA; 2) Center for Brain Science, Harvard University, Cambridge, MA; 3) Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA.

   Flies exhibit personalities (persistent, idiosyncratic behavioral tendencies) just like humans. Whereas considerable progress has been made in identifying the molecular and neurobiological bases of averaged, population-level behaviors, mechanisms underlying individual-to-individual variation in behavior are largely unknown. We developed a suite of high-throughput ethological rigs capable of characterizing the behaviors of many flies, individually. Focusing on the simple behaviors of phototaxis and locomotor handedness, we find profound levels of behavioral heterogeneity. These idiosyncrasies constitute fly personality since they persist throughout the flies' lifespan. Interestingly, in all cases tested, idiosyncratic behaviors of parent flies were not inherited by their progeny. Using the Drosophila transgenic and pharmacological toolkits, we have identified several molecular and circuit determinants of the magnitude of behavioral variability. Specifically, the White pathway and serotonin suppress phototactic personality, and neural activity in small field neurons of the protocerebral bridges suppresses personality with respect to locomotor handedness. The implication of neurotransmitters and specific neural circuits as regulators of behavioral diversity raises the intriguing possibility that flies can dynamically modulate their population-level behavioral diversity, perhaps as an adaptive response to environmental cues. Lastly, we have conducted a genome-wide association study to identify genetic loci regulating the magnitude of personality. This was only possible because we observed variation (across lines) in the degree of behavioral variation (within lines). Preliminary results implicate a number of genes preferentially expressed in the brain, consistent with the effects of pharmacological and targeted circuit manipulation.