Molecular mechanisms underlying the evolution of central neural circuits and behaviour

The immense variety of behaviours displayed by animals – including ourselves- arose through the evolution of neural circuits within the brain. However, how central neuronal circuits change over time, integrating these modifications within the brain's highly interconnected networks remains largely unknown. Particularly puzzling is that evolution acts at the level of the genome but behaviour arises through the activity of neuronal networks. How are these two levels integrated? How do evolutionary changes on the genome lead to changes in neuronal circuits that themselves lead to behavioural divergences across animals? The larval olfactory system of Drosophila provides a powerful model to address these questions because: 1) different Drosophila species have evolved diverse odour-guided behaviours, 2) the olfactory system is numerically simple yet parallels more complex circuits, and 3) the availability of molecular tools and resources. I will use this system to identify hotspots of central neuronal circuit evolution at both functional and genetic levels by comparing two Drosophila species. First, leveraging comparative connectomic data from the host lab, I will use calcium imaging and modelling to examine the functional impact of cross-species connectomic changes. Second, I will employ a combination of transcriptomic approaches to determine the molecular changes that lead to functional and connectivity differences. Finally, I will apply these insights to re-engineer the neuronal circuits across species by making use of the genetic tools available in D. melanogaster. This research will enhance our understanding of the intricate interactions between genes, neuronal circuits, and behaviour in the context of evolution.