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SYNAPTIC MECHANISMS FOR BASIC AUDITORY PROCESSING
by
Guangying Wu
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(NEUROSCIENCE)
May 2009
Copyright 2009 Guangying Wu
Object Description
| Title | Synaptic mechanisms for basic auditory processing |
| Author | Wu, Guangying |
| Author email | guangyiw@usc.edu; guangying@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Neuroscience |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2008-12-02 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-02-13 |
| Advisor (committee chair) | Zhang, Li I. |
| Advisor (committee member) |
Chen, Jeannie Chow, Robert H. Sampath, Alapakkam P. Langen, Ralf |
| Abstract | Neurons are organized into circuits to process various information in the brain. To understand how information is processed, it's fundamental to investigate the patterns of excitatory and inhibitory inputs underlying neuron's response properties. Through the four independent but closely related studies described in my dissertation, I investigated the synaptic mechanisms underlying basic response properties of rat auditory neurons, i.e. frequency tuning, intensity tuning and temporal coding. Firstly, we developed a novel method to silencing the cortex and dissected the excitatory input from thalamic neurons and that from cortical excitatory neurons. The results demonstrated that thalamic input had a flattened frequency tuning curve. In contrast, intracortical excitatory input was sharply tuned with a tuning curve that closely matched that of suprathreshold responses. It suggests the recurrent excitatory circuits define the cortical frequency tuning. Secondly, to study the cortical inhibitory neurons, we combined single-unit cell-attached recording, juxtacellular labeling and whole-cell recording together on the same neuron in vivo. We discovered that the frequency tuning curve of inhibitory input was broader than that of excitatory input. So a relatively stronger inhibition was flanked to the preferred frequencies of the cell and laterally sharpened the frequency tuning of membrane responses. The less selective inhibition can be attributed to a broader bandwidth and lower threshold of spike tonal receptive field of fast-spike inhibitory neurons than nearby excitatory neurons. Thirdly, we uncovered the synaptic mechanisms underlying cortical intensity tuning. The results demonstrated that excitatory inputs to those intensity-tuned neurons have already shown a weak tuning, while inhibitory inputs suppressed the excitation at higher intensities to strengthen the tuning through a dynamic temporal control.; Finally, we turned to cochlear nuclei neurons in the brain stem to study the mechanisms underlying duration properties. The results demonstrated neurons here had sustained excitatory and inhibitory inputs. But the imbalanced excitation and inhibition in temporal aspect generated a more precise response to represent duration information. Bringing all the previous studies together, the interaction and dynamics between excitation and inhibition can work together to shape the response properties and guarantee a faithful representation of sensory world. |
| Keyword | auditory processing; in vivo whole cell recording; intensity tuning; frequency tuning; duration coding |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1975 |
| Rights | Wu, Guangying |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Wu-2449 |
| Archival file | uscthesesreloadpub_Volume32/etd-Wu-2449.pdf |
Description
| Title | Page 1 |
| Full text | SYNAPTIC MECHANISMS FOR BASIC AUDITORY PROCESSING by Guangying Wu A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (NEUROSCIENCE) May 2009 Copyright 2009 Guangying Wu |
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