A neuronal circuit mediating state-dependent behavioral decisions

• Applicant: Mert Erginkaya, Ph.D.
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567925412

Animals must negotiate dynamic and complex environments to survive. This requires integrating external sensory cues with ever-changing internal demands to make optimal decisions on a moment-by-moment basis. How brain circuits integrate external sensory cues with the internal state — whether the animal is active or at rest, hungry or satiated, afraid or calm — is a fundamental, open question in neuroscience. In this project, I will investigate how the locomotor state (flying or perching) influences decision-making in the fruit fly Drosophila, by focusing on the choice between two opposing behaviors: landing or take-off in response to a visual looming stimulus. To address this, I will combine a detailed analysis of brain connectivity, neural activity recordings, and behavioral experiments to achieve three main objectives: First, I will Identify visuomotor circuits that integrate locomotor state information in decision-making processes. To this end, I will map the neural pathways linking visual processing to motor circuits descending into the ventral nerve cord (the fly's analogue to the spinal cord), reconstructing the connectivity of key neurons involved in landing and take-off behaviors induced by a looming stimulus. This will provide a circuit blueprint for how state-dependent sensory processing enables flexible action-selection. Second, I will determine how locomotor state affects behavioral decisions. To do so, I will test whether neuromodulatory signals — particularly octopamine — alter the likelihood of a fly choosing to land or take-off when faced with a visual looming stimulus. By manipulating octopaminergic neurons and recording behavioral responses, I will determine how the internal state biases this decision. Third, I will characterize how the locomotor state affects sensorimotor processing. Using electrophysiological recordings from neurons that either induce landing or take-off, I will examine how state-dependent neuromodulation influences neuronal activity in descending motor circuits. This will reveal how the locomotor state alters the neuronal computations that drive action selection. By dissecting these mechanisms at the level of individual neurons, my project will provide new insights into how brains adjust behavior based on internal states — a fundamental process relevant to many animals, including humans.

• DFG Programme: WBP Position