Project Summary Normal sleep and circadian rhythms play a critical role in the developing brain. Disruptions in sleep and rhythms during human development are a common co-morbidity in neurodevelopmental disorders including ADHD and autism. Although the molecular mechanisms encoding cellular rhythms are well understood, little is known about how rhythmic behaviors first emerge. I hypothesize that the developmental emergence of rhythmic behaviors is intimately tied to metabolic state. Specifically, juvenile animals have high metabolic demands necessitating frequent feeding; as an animal matures, consolidated periods of sleep become sustainable, leading to enhanced memory capacity. However, it is unclear how changes in metabolic state influence the emergence of behavioral rhythms or if the neural circuitry that regulates rhythmic behavior has conserved functions across the lifespan. This proposal exploits the Drosophila melanogaster model to investigate the mechanism through which sleep and feeding rhythms are initiated and influenced by metabolic state. This proposal will also offer insight into how long-term memories (LTM) are coupled to rhythmic sleep. Finally, this proposal will use a developmental approach to examine how sleep-wake and feeding rhythms are regulated across the lifespan. I have determined that while 2nd instar (L2) Drosophila larvae do not show differences in sleep across the day, early 3rd instar (L3) larvae show clear diurnal differences, sleeping more at night. My preliminary data have characterized the development of a circuit bridge between larval DN1a clock neurons and Dh44(+) output neurons that drives the emergence of sleep rhythms. I have also determined that Drosophila larvae experience changes in LTM capacity over development: L3 but not L2 larvae exhibit LTM of an aversive cue. In the mentored phase of this proposal, I will determine if the DN1a-Dh44 circuit acts as a conserved regulator of sleep timing across the lifespan (Aim 1) and I will uncover how circadian sleep-wake circuitry communicates with learning/memory circuits to promote the development of LTM capacity (Aim 2). In the independent phase of this proposal, I will determine how metabolic state influences circadian-sleep circuit development (Aim 3) and how other rhythmic behaviors such as feeding develop (Aim 4). Completion of the proposed experiments will provide insight into how developing circuits integrate metabolic cues to drive the emergence of rhythmic behavior. Broadly, this proposal will provide rigorous training 1) in a wide range of behavioral analyses possible in Drosophila including adult sleep, 2) feeding rhythms and circadian neurobiology, 3) larval learning/memory principles and circuitry, and 4) cutting-edge techniques such as machine learning/vision approaches, each of which will complement my existing knowledge/skills. Completion of the proposed training plan will open the door for new areas of investigation in Drosophila in my own indepe...