Extended Flight Bouts Require Disinhibition from GABAergic Mushroom Body Neurons

Abstract

Insect flight is a complex behavior that requires the integration of multiple sensory inputs with flight motor output. Although previous genetic studies identified central brain monoaminergic neurons that modulate Drosophila flight, neuro-modulatory circuits underlying sustained flight bouts remain unexplored. Certain classes of dopaminergic and octopaminergic neurons that project to the mushroom body, a higher integrating center in the insect brain, are known to modify neuronal output based on contextual cues and thereby organismal behavior. This study focuses on how monoaminergic modulation of mushroom body GABAergic output neurons (MBONs) regulates the duration of flight bouts. Octopaminergic neurons in the sub-esophageal zone stimulate central dopaminergic neurons (protocerebral anterior medial, PAM) that project to GABAergic MBONs. Either inhibition of octopaminergic and dopaminergic neurons or activation of GABAergic MBONs reduces the duration of flight bouts. Moreover, activity in the PAM neurons inhibits the GABAergic MBONs. Our data suggest that disinhibition of the identified neural circuit very likely occurs after flight initiation and is required to maintain the "flight state" when searching for distant sites, possibly related to food sources, mating partners, or a suitable egg-laying site. VIDEO ABSTRACT.