CRCNS: Formation of stimulus selective neural assemblies in piriform cortex

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Sensory cortex decomposes complex inputs into feature-based components, and distributes their representation over populations of neurons. In special cases this distribution is very clear--for instance the visual and auditory system respectively map retinal image and acoustic frequency along a spatial dimension within cortex. In general, however, rich sensory scenes are a mixture of features, and it remains unclear how the cortex mingles and segregates aspects of a complex sensory representation across neural populations. Olfactory stimuli are extraordinarily complex, with distinct odors comprised from a mixture of compounds. The circuitry in olfactory cortex is equally intricate, with populations of neurons coupling to one another with seemingly random rules, and receiving similarly random projections from lower centers. The combination of these two facts obfuscates the organization of odor representation. Our proposal leverages advances in experimental circuit identification and manipulation, as well as theoretical frameworks for large-scale cortical networks, to establish principles for the distribution of odor identity and concentration coding across olfactory cortex. Specifically, we aim to establish the following links between olfactory circuitry and odor coding: 1 )There exists a graded distribution of specific inhibitory sub-circuits along the rostral-caudal axis of the olfactory cortex. 2) The rostral-caudal distribution of inhibition interacts with Hebbian plasticity mechanisms so as to shape the odor selectivity of cells along the rostral-caudal axis. These advances will provide much needed insights into how cortical structures represent and process distinct aspects of an odor scene.