Ahmed et al. took advantage of developmental changes in the mushroom body to study and test the proposed expansion layer model. They called it “developmental hacking of circuit wiring” to change input density of Kenyon cells in the mushroom body. They used hydroxyurea to stochastically ablate kenyon cell neuroblasts during development. This would remove large numbers of kenyon cells but in various amounts on an individual basis. They tested whether these flies could still learn using a 2 choice odor task then immunostained individual’s brains to quantify learning deficit in response to decreased KCs.
They found that learning performance was not correlated to KC numbers, confirming previous work that odor is encoded through population level activity. However, less KC input density made odor presentation less robust. The flies were still able to learn but have more difficulty discriminating similar odors.
references
- Ahmed, M., Rajagopalan, A. E., Pan, Y., Li, Y., Williams, D. L., Pedersen, E. A., Thakral, M., Previero, A., Close, K. C., Christoforou, C. P., Cai, D., Turner, G. C., & Clowney, E. J. (2023). Input density tunes Kenyon cell sensory responses in the Drosophila mushroom body. Current Biology, 33(13), 2742-2760.e12. https://doi.org/10.1016/j.cub.2023.05.064