The microRNA bantam regulates excitability in adult mushroom body output neurons to promote early night sleep.

Sleep circuitry evolved to have both dedicated and context-dependent modulatory elements. Identifying modulatory subcircuits and understanding their molecular machinery is a major challenge for the sleep field. Previously, we identified 25 sleep-regulating microRNAs in , including the developmentally important microRNA . Here we show that acts in the adult to promote early nighttime sleep through a population of glutamatergic neurons that is intimately involved in applying contextual information to behaviors, the γ5β'2a/β'2mp/β'2mp_bilateral Mushroom Body Output Neurons (MBONs). Calcium imaging revealed that bantam inhibits the activity of these cells during the early night, but not the day. Blocking synaptic transmission in these MBONs rescued the effect of knockdown. This suggests promotes early night sleep via inhibition of the γ5β'2a/β'2mp/β'2mp_bilateral MBONs. RNAseq identifies and as possible mediators, establishing a new role for as an active regulator of sleep and neural activity in the adult fly.