Optical techniques for studying rodent olfaction

The mouse olfactory system is an ideal sensory modality for the study of neural circuits. Understanding how the olfactory system encodes a vast number of odors uniquely is key to understanding efficient neural coding as well as an important step in creating artificial noses. Olfaction is also affected early on in neurodegenerative diseases such as Alzheimer's and Parkinson's, making it a possible model neural system for understanding disease and aging-induced alterations in neural processing. However, it is a technically difficult system to study both in the terms of control and readout of neural activity. Odorants are encoded by the simultaneous activation of 1000s of information channels. Furthermore, the tuning curves for these channels is not fully known. Odorants are also discrete and immutable; one cannot simply use the olfactory equivalent of a projector or a speaker to recreate the full range of stimuli, from simple monomolecular odorants to complex near-natural scenes. To address these issues in the acute slice preparation, I developed an all-optical approach to studying the connectivity of the olfactory system. With this technique, both the control of olfactory input channels as well as readout of individual cells can be performed entirely with light. This method allows researchers to stimulate the olfactory system in a combinatorial manner in slices, more closely mimicking natural stimuli. Furthermore, I automated the data acquisition software and designed optics for use in vivo. Finally, I developed a head-restraining paradigm to aid the study of olfaction in awake, behaving mice, a key step in bridging the gap between cellular neural activity in response to odor molecules and an animal's percepts.