looming circuits have been well studied for many years. the visual information about the looming stimulus is detected by different groups of LCs, including LPLC2 and LC4. | LCs convey specific visual features to the brain. These LCs directly synapse onto the giant fiber descending neuron | the giant fiber receives looming visual input from LPLC2.
the giant fiber then connects to circuits in the VNC to initiate takeoff.
But depending on behavioral state, looming may initiate landing or takeoff — see Ache.etal2019
references
Wu.etal2016
Klapoetke.etal2017
Von Reyn, C. R., Nern, A., Williamson, W. R., Breads, P., Wu, M., Namiki, S., & Card, G. M. (2017). Feature Integration Drives Probabilistic Behavior in the Drosophila Escape Response. Neuron, 94(6), 1190-1204.e6. https://doi.org/10.1016/j.neuron.2017.05.036