Learning-mediated plasticity in cortical feedback projections to the olfactory bulb

To reliably encode information about the environment, neurons must modify their activity profiles and even connectivity to accurately interpret complex stimuli. Cortical feedback projections to the olfactory bulb are uniquely positioned at the interface between detection-based processing that is driven by sensory input and analytical processing occurring in the piriform cortex. This makes these projections an ideal target to study how learning reshapes neuronal activity profiles. We have developed an approach that will allow for a comprehensive analysis of the axonal activity of principal neurons in the piriform cortex, while mice learn a task requiring them to identify a specific odor embedded in complex mixtures.

Our technical approach uses animal behavior, patch-clamp electrophysiology, and in vivo imaging to study these cells and circuits.

Information coding in olfactory sensory neurons

Animals, including humans, interact with their chemical environment through specialized receptor cells found within the nasal epithelium. Upon odorant binding, these neurons transmit information to the olfactory bulb, the initial site of sensory processing in the olfactory system. However, our understanding of how these cells ultimately communicate information about odor identity and concentration to the brain is limited.

In our past work, we first developed a theoretical framework describing how blends of odor stimuli are detected and encoded by olfactory sensory neurons, with a focus on antagonistic interactions. We then tested the hypotheses generated by our model using in vivo calcium imaging to measure the stimulus-evoked activity in olfactory sensory neurons in live animals. Our work so far has begun to reveal that olfactory sensory neurons are far from simple relays and that their nonlinear interactions fundamentally affect olfactory processing. Another component of this project will investigate the role of ion channels downstream of odor receptor binding and their contribution to how olfactory sensory neurons detect odors and transmit odor information to the brain.

This project uses both animal behavior and in vivo imaging techniques.