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Modulation in olfaction: How recurrent circuits govern state-dependent behaviour


Hunger and reproduction are arguably the two most relevant drives in animal behaviour. Most species – from worms to insects to mammals – heavily rely on olfaction to follow these drives, i.e. to retrieve food and find suitable mating partners. Conversely, metabolic and reproductive states modulate odour perception according to the animal’s behavioural and physiological needs, along with its actual state of general arousal. While we start to understand primary feed-forward processing in olfaction, the function of the many short- and long-range recurrent connections - in part counter to the sensory stream - that are revealed in more and more detail in olfactory systems across phylae remains elusive. Here we propose that these different types of recurrent circuit motifs play an important modulatory role in state-dependent olfactory processing, perception and behaviour. The aim of this initiative is, therefore, to test this hypothesis experimentally in distant animal models (insects versus rodents), from the level of the neuroanatomy of the underlying recurrent circuits, their individual synaptic connectivity and physiology, the modulation of the ensemble activity of principal neurons, to the modulation of perception and behaviour by exemplary fundamental state-dependent variables, i.e. hunger, reproductive drive, arousal, and experience.



To achieve this goal, we will jointly develop, standardize and optimize methods, with a special focus on precise control of the olfactory stimulus and on recording techniques suitable for studying recurrent circuit motifs. The expected outcomes of our ambitious research project will be relevant not only for olfactory processing but will reveal essential rules and mechanisms for the function of recurrent connections within the entire nervous system.