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DYNAMICS OF SPIKE-TIMING AND GAMMA OSCILLATIONS IN THE OLFACTORY BULB

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Abstract

In the mammalian olfactory bulb (OB), gamma oscillations that are generated endogenously during odor sampling indicate that neuronal population activity becomes intrinsically synchronized at fine timescales in response to sensory inputs. While the circuit-level mechanisms generating gamma oscillations in the bulb are fairly well-described, the functional role of this oscillatory synchrony in odor representations remains unclear. How are patterns of spiking activity shaped by the OB’s intrinsic dynamics during odor responses, and could this serve to transform the coding metric of odor information in the OB? To address these questions, this dissertation investigates spike-timing dynamics in the OB using a specialized optogenetics-electrophysiology rig I developed for this purpose. This rig system enables controlled delivery of spatiotemporally precise, patterned light stimulation to brain slices while recording neuronal population activity across a large region of the slice using 120-channel planar microelectrode arrays. Utilizing this system, I presented “fictive odors” generated via patterned optogenetic stimulation of olfactory sensory neuron axonal arbors in OB slices, and examined spike-timing dynamics in the stimulus responses. During fictive odor presentation, a small proportion of odor-encoding mitral/tufted cells phase-locked to gamma oscillations evoked by the fictive odor, and exhibited tightly coupled spike-spike synchrony on a gamma timescale. Moreover, the synchronized ensemble of neurons varied based on the “quality” of the odor, but not the “concentration”, and was conserved across multiple trials of the same fictive odor. Based on these response properties, I propose that gamma timescale spike synchrony is a metric by which the OB encodes and exports odor information in a concentration-invariant manner. In another empirical article, we investigated the impact of perineuronal networks (PNNS) on bulbar dynamics. Histological staining revealed PNNs in select glomeruli of the OB, and surrounding putative mitral cell axon initial segments. Enzymatic removal of PNNs in acute OB slices altered the variability of spike-timing, and attenuated gamma power in the local field potential – indicating the presence of PNNs in the OB may have the capacity to influence early odor processing.

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121 pages

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Date Issued

2023-08

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Keywords

Gamma Oscillations; Olfactory bulb; Slice physiology; Spike-timing

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Union Local

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Committee Chair

Cleland, Thomas

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Committee Member

Linster, Christiane
Smith, David
Field, David
Krosch, Amy

Degree Discipline

Psychology

Degree Name

Ph. D., Psychology

Degree Level

Doctor of Philosophy

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Government Document

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Attribution 4.0 International

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dissertation or thesis

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