Effects of olfactory sensory experience on plasticity of neuron-type specific circuits

The anterior piriform cortex (APC) is the largest area of olfactory cortex and plays a major role in representing odor sensory features as well as value. How are neurons and circuits wired up to mediate extraction of distinct odor features in the same brain region? Even though there is little evidence for a map in the longitudinal axis of APC (horizontally), there is strong organization in the laminar axis (vertically). Two major classes of neurons have been identified in layer 2 of APC: semilunar (SL) and superficial pyramidal (SP) cells. SL and SP cells differ in the input connectivity, output connectivity, and passive neurophysiological properties, and they can be two different channels for extracting different odor information. However, it is unclear how SL vs. SP cells are recruited by neural activity and activity-dependent plasticity. Here we hypothesize that the plasticity and wiring of GABAergic interneurons toward SL vs. SP cells are a key mechanism. We used a combination of naris occlusion, immunofluorescent staining, electrophysiology and optogenetics to probe the effects of olfactory sensory activity on SL vs. SP cell plasticity. Immunofluorescent labeling for GABAergic markers suggested that activity deprivation modulated the expression of proteins in the ipsilateral APC since the majority of neural activity is propagated unilaterally. We are in the process of evaluating excitation-inhibition balance in the APC circuits using slice electrophysiology. In summary, uncovering the principles of neuron-type specific plasticity in the APC will yield likely important insights about how SL vs. SP cells extract different information from olfactory bulb input.