Author ORCID Identifier

Defense Date


Document Type


Degree Name

Doctor of Philosophy


Systems Modeling and Analysis

First Advisor

Cheng Ly


Odor perception is the impetus for important animal behaviors, most pertinently for feeding, but also for mating and communication. There are two predominate modes of odor processing: odors pass through the front of nose (ortho) while inhaling and sniffing, or through the rear (retro) during exhalation and while eating and drinking. Despite the importance of olfaction for an animal’s well-being and specifically that ortho and retro naturally occur, it is unknown whether the modality (ortho versus retro) is transmitted to cortical brain regions, which could significantly instruct how odors are processed. Prior imaging studies show different brain activity for the two modes, even with identical odors. However, odors are first processed via coordinated spiking of neurons in the olfactory bulb (OB) before being relayed downstream to higher cortical regions. Thus, we investigate responses of mitral cells (MC), one of principle neurons in OB, to ortho and retro stimulus to elucidate how the OB processes and codes this information.

We analyze our collected in vivo rat data to inform modeling of the OB circuitry and MC responses to both modes of olfaction. Our efforts show that the OB does indeed process odors differently and that the temporal profile of each stimulus route to the OB is crucial for distinguishing ortho and retro odors. Additionally, we detail the rich spiking dynamics observed in our MC model and use a phenomenological model to explain the unexpected non-monotonic spike variability observed as weak-to-moderate background noise increases. Lastly in both anesthetized and awake rodents, we show that MCs with synaptic connections to cortical regions reliably transmit ortho versus retro input stimulus information. Drug manipulation affecting GABAA-mediated synaptic inhibition leads to changes in decoding of ortho/retro and only affects firing response for one of the two modes. We have not only shown that ortho versus retro information is encoded to downstream brain regions, but with models and analysis, we uncover the network dynamics that promote this encoding.


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