ERC Starting Grant goes to Bettina Schnell for her studies on how tiny fly brains make decisions

Bettina Schnell, head of the research group Neurobiology of Flight Control, has been awarded a prestigious Starting Grant from the European Research Council (ERC). With a funding volume of 1.5 million euros, her research project will contribute to understanding how animals make behavioral decisions.

While sensory systems report sensory input with high reliability, behavioral responses are inherently variable. How does this variability arise? It is obvious that the internal state of the animal also matters in addition to external stimuli. For example, when an animal is very hungry, it reacts differently to food stimuli compared to when it has just been feeding. But how exactly does an animal make decisions? This is still not completely understood in any organism.

In the project "MOBY-FLY", the researchers investigate the role played by both external stimuli and the animal's current internal state in the fruit fly Drosophila. Flies can perform extremely fast turns during flight, the so-called saccades. They use this behavior mainly to avoid danger, but also when searching for food. Even though the nervous system of the tiny fly is very well characterized, we still do not know which neuronal network underlies this fascinating capability. Bettina Schnell recently already identified one descending neuron, whose activity clearly correlates with saccadic turns. Now she aims to find out which neurons in turn provide input for this descending neuron and how they are connected.

To this end, the research group will first identify the respective neurons anatomically and then measure their activity using patch-clamp recordings as well as 2-photon calcium imaging during tethered flight. Using different stimuli, they will test if the activity of the individual neurons correlates more with the external stimuli or the animal’s behavioral output. In addition, they will genetically switch on or off individual neurons selectively in free flight to further characterize their function. This comprehensive approach aims to unravel at which level of the circuitry - from sensory input to motor output - it is no longer the external stimuli only that play a role, in other words at which point the variability of behavior is generated.