Co-evolution and circuit integration of mushroom bodies and central complex
Evolutionary Cell and Developmental Biology (Zoology)
Cognitive, Systems and Behavioural Neurobiology
Final Report Abstract
In my project I aimed to examine mechanisms that explain patterns of constraints and adaptability in neural tissue and circuitry by using the shared circuit of mushroom bodies (the brain area responsible for learning and memory) and the central complex (the brain area responsible for spatial navigation) as model system. I used a large radiation of butterfly species, the Heliconiini, to examine these mechanisms in the mushroom body-central complex circuit, as some members of this butterfly tribe feed on pollen, which is concomitant with a massive increase in mushroom body volume. In contrast to this massive increase, central complex investment seemingly stayed the same. I first used a large data set of immunostainings and mass injections to generate careful anatomical descriptions, to then draw statistical inferences about differential investment of mushroom body circuit components. Indeed, some Kenyon cell types (the major cell type in mushroom bodies) have expanded with higher rates than others. Similarly, some supporting cell types, specifically the GABA-ergic inhibitory feedback neurons, expanded in cell number while dopaminergic neurons were conserved. This pattern of differential expansion mirrors mosaic models of brain evolution, but now put them into a circuit context inside a brain area, rather than across several. The central complex in contrast to the mushroom bodies showed a conserved volumetric investment, but we identified a series of distinct anatomical differences. We put both projects in a wider context by speculating about what overarching developmental and genetic mechanisms allow some cognitive circuits to change while others stay the same. My results as part of my Walter-Benjamin Fellowship identify novel mechanistic insights into the evolution of brains and circuits and lay important groundwork for future experiments.
Publications
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An atlas of the developing Tribolium castaneum brain reveals conservation in anatomy and divergence in timing to Drosophila melanogaster. Journal of Comparative Neurology, 530(13), 2335-2371.
Farnworth, Max S.; Bucher, Gregor & Hartenstein, Volker
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Complexity of biological scaling suggests an absence of systematic trade-offs between sensory modalities in Drosophila. Nature Communications, 13(1).
Farnworth, Max S. & Montgomery, Stephen H.
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Evolution of neural circuitry and cognition. Biology Letters, 20(5).
Farnworth, Max S. & Montgomery, Stephen H.
