Recurrent connections between higher olfactory brain areas and their role in mating state-dependent behaviour in Drosophila

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Internal states strongly influence sensory perception and thereby an animal’s interpretation of the world around it. In project TP3, we focus on a highly important change in internal state, motherhood, and the recurrent circuit mechanisms of how it changes female olfactory perception and behaviour. Female Drosophila melanogaster drastically change behaviour shortly after mating and prioritize finding appropriate egglaying sites rich in nutrients. For finding such sites, females rely on the sense of smell to detect key odorants including the putrid odour of polyamines. Importantly, her preference for polyamines is modulated by mating such that a mated female will prefer higher concentrations of the odour for ~2 weeks after mating. We have previously shown that mating induces changes at several levels in olfactory processing. First, a mating-induced peptidergic signalling modulates polyamine sensing in olfactory sensory neurons. Second, mating also changes higher processing through modulation of specific mushroom body (MB)-innervating dopaminergic neurons (DANs). Most recently, we found that the long-lasting change in mating-induced polyamine perception requires the MB not only for the expression of a changed preference but, surprisingly, also for its mating-related induction. Our latest data suggest that local and long-range recurrent connections between MB output neurons (MBON) and DANs, and MBONs and neurons of the lateral horn (LH) are critical for either induction or expression of higher polyamine preference or both. Here, we will combine behavioural analysis, genetic manipulation, and state-of-the-art in vivo functional imaging with recent connectomics data to map and functionally characterize these recurrent circuit motifs in reproductive state-dependent odour perception in female animals.