Role of anterior olfactory nucleus for multi-sensory integration in the olfactory system

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Project Summary Sensory signals encountered under different circumstances may have quite different implications. In the early olfactory system, preliminary evidence suggests that this (non-olfactory) contextual information is integrated into odor representations at a very early stage, potentially even the main olfactory bulb. Recent evidence indicates that the anterior olfactory nucleus (AON), a structure directly adjoining the olfactory bulb, serves to integrate afferent odor information with contextual information from the ventral hippocampus (vHC) and is necessary to solve contextually-dependent olfactory decision-making tasks. The vHC is known to relay task-relevant spatial contextual information to other brain systems. We here hypothesize that direct projections from the vHC to the AON play a dominant role in the integration of contextual and olfactory information, and that the AON embeds this multisensory contextual information into early-stage odor representations. Our preliminary data show that rodents can learn to respond differently to odors based on the spatial context in which they are encountered, and that the expression of such a rule depends on both AON and vHC, whereas a similar but odor-independent task requires vHC but not AON. We propose a multipronged approach to understanding the integration of spatial context into olfactory representations, engaging electrophysiological ensemble recordings and interareal coherence measurements in awake, behaving rodents, the optogenetic manipulation of vHC and AON circuit activities, and a double-labeling strategy for the within-subjects comparison of immediate-early gene (Fos) responses across two experimental conditions separated in time. Supplement summary: Piriform cortex (PC), is tightly interconnected with OB, AON and vHC and potentially involved in similar processed. The additional Aims planned include testing the hypothesis that PC performs complementary functions to AON and is involved in contextual processing.