Date of Award
Doctor of Philosophy (PhD)
Max L. Fletcher, PhD
John D. Boughter, PhD; Matthew Ennis, PhD; Detlef H. Heck, PhD; Lindsay A. Schwarz, PhD
animal behavior, calcium imaging, habituation, learning and memory, miniscope, olfactory coding
The piriform cortex (PC) has long been established as the primary cortical recipient of olfactory information in the mammalian brain. In rodents, information extracted from recordings of PC neurons can accurately decode the identity of odors, leading to delineation of PC as the primary cortical region involved in the formation of odor perception. Unfortunately, due to technical limitations, many of the prior studies establishing these coding principles were performed without the ability to track the responses of the same cells over time. Additionally, recordings have often relied on head-fixation to minimize diffusion of odor stimuli, limiting movement range and natural behavior of subjects in the process. The primary goal of the work presented in this dissertation was to expand on these prior studies by implementing tools to record from or manipulate conserved PC populations during naturalistic odor experience and odor-driven behavior. We found that, despite an immense volume of background PC activity in freely moving animals, odor responses can be isolated from recordings and contain sufficient information to decode odor identity within a session. Across days, however, the tuning of individual cells was often inconsistent, leading to decreases in classification accuracy. Importantly, attention to the odor was correlated with greater response consistency across days, indicating a role for behavioral state of the animal in modulating odor coding. Our results support recent evidence of representational drift in PC, but also indicate the possibility that animal behavior can influence response profiles. In a separate experiment, manipulation of olfactory bulb (OB) feedback from PC was unable to disrupt odor discrimination but did impair acquisition of a fear memory. This supports prior work from other labs indicating a role for PC in olfactory learning, expanding its role in olfactory processing. In total, this work highlights the need for more studies to clarify the coding strategies implemented by PC in olfactory processing.
Chapman, Ian F. (https://orcid.org/0000-0002-8532-392X), "Olfactory Processing in the Piriform Cortex of Awake, Freely Moving Mice" (2022). Theses and Dissertations (ETD). Paper 620. http://dx.doi.org/10.21007/etd.cghs.2022.0607.
Available for download on Friday, January 10, 2025