A Systems Level Analysis of Neuronal Network Function in the Olfactory Bulb: Coding, Connectivity, and Modular organization

A Systems Level Analysis of Neuronal Network Function in the Olfactory Bulb: Coding, Connectivity, and Modular organization

by Tsai-Wen Chen
Doctoral thesis
Date of Examination:2008-05-08
Date of issue:2008-12-15
Advisor:Prof. Dr. Dr. Detlev Schild
Referee:Prof. Dr. Fred Wolf
Referee:Prof. Dr. Walter Stühmer
Persistent Address: http://dx.doi.org/10.53846/goediss-3468

 

 

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Abstract

English

The olfactory bulb (OB) is the first brain region that receives and processes sensory inputs from the nose. It contains highly specialized neuronal networks organized by individual glomeruli, which are sites of synaptic contacts between olfactory sensory neurons (OSN) and secondary mitral/tufted (M/T) cells in the OB. In this thesis, I explored the neuronal network function of a vertebrate OB system, using a combination of calcium imaging and electrophysiological techniques. In the first part of the thesis, I introduced a number of image processing techniques for analyzing functional calcium imaging data. This facilitates the selection of regions of interest and allows visualizing fine processes of neurons in densely stained brain tissues. In the second part of the thesis, we explored the dynamics of [Ca2+] activity of M/T cell population. This led to the identification of distinct subpopulations of neurons that showed highly synchronous spontaneous [Ca2+] activity. Anatomical reconstruction revealed that these synchronous neurons were invariably connected to the same glomerulus. Furthermore, the odor-induced responses of synchronous neurons were virtually identical, irrespective of whether the responses were excitatory or inhibitory, and irrespective of the distance between them. In the third part of the thesis, we analyzed the mechanism underlying the synchronous responses. We show that synchronous neurons received correlated EPSC inputs and were coupled by gap junctions. Together, these data reveal that odors are represented in the OB by modules of distributed and synchronous M/T cells associated with the same glomeruli. This may allow for parallel input to higher brain centers.
Keywords: Calcium imaging; Olfactory bulb; Mitral Cell; Synchronous activity; Glomerulus; Neuronal Network; Image Processing
Schlagwörter: Calcium imaging; Olfactory bulb; Mitral Cell; Synchronous activity; Glomerulus; Neuronal Network; Image Processing
 
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