Top-down (State dependent) Modulation of Sensory Processing in the Mouse Olfactory Bulb

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Sensory processing in the brain is not fixed and involves countercurrent streams of information flow. In the “bottom-up” pathway, sensory information is shaped and refined as it travels from primary sensory to higher brain centers. However, information is also relayed back to influence sensory processing in more specialized brain areas (“top-down” processing). Through top-down processes, factors like experience, motivation and expectation, i.e., the general “brain state”, affect sensory processing and, thereby, our internal representation of the world. However, the neuronal mechanism involved in top-down modulations and the relative contribution of top-down systems to complex behavioral tasks are not well understood.In order to study top-down modulations of sensory processing the mouse olfactory pathway is an ideal vertebrate model system: the olfactory pathway is targeted by all major top-down systems and mice largely rely on olfaction for orientation allowing defined behavioural tests to be combined with a wide variety of innovative genetic tools. This one year project is based on the results obtained during the first period of Emmy Noether funding (see Zwischenevaluation) and will investigate the behavioral consequences of manipulating activity of two major top-down systems for the awake animal. We hypothesize that an extrinsic modulation of top-down activity in the awake behaving animal will exert distinct effects on perceptual discrimination and therefore allow us to test for causal relationships between top-down circuits and behavioural performance. In summary, this project is aimed at transferring our results obtained in the anesthetised preparation to the awake condition and therefore represents an important cornerstone for the Emmy Noether project.