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AN IN VITRO MODEL OF A RETINAL PROSTHESIS
by
Ashish Kishore Ahuja
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
(ELECTRICAL ENGINEERING)
May 2007
Copyright 2007 Ashish Kishore Ahuja
Object Description
| Title | An in vitro model of a retinal prosthesis |
| Author | Ahuja, Ashish Kishore |
| Author email | ashishah@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-01-24 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-04-23 |
| Advisor (committee chair) | Choma, John |
| Advisor (committee member) |
Weiland, James Tanguay, Armand Steier, William Berger, Theodore |
| Abstract | The electrode-retina interface of an epi-retinal prosthesis implant has been studied using finite-element modeling, electrochemical methods, and retinal array electrophysiology. The studies presented in this thesis have relied on the flexibility of custom designed and microfabricated multielectrode arrays to investigate the current distribution at the electrode-electrolyte interface and it's interaction with retinal tissue.; A flexible photolithographic microfabrication process flow has been optimized for the fabrication of conformal MEAs for hippocampal and retinal slice electrophysiological experiments. (Seven different electrode pad layouts were used in the fabrication of various arrays.) Electrostatic finite-element modeling was used to model the inhomogeneous current distribution at the electrode surface.; Using cyclic voltammetry (CV), biphasic pulsing, and electrochemical impedance spectroscopy (EIS) it has been shown that (1) microelectrodes with diameters less than or equal to 100 µm exhibit increased charge density, and (2) that the impedance of microelectrodes transitions from a perimeter to an area dependent regime as the frequency is decreased from 100 KHz to 10 Hz. The later, proves that the current distribution at the electrode surface is dynamic, and evolves during the time course of a stimulus pulse.; MEAs with 200 µm diameter stimulating electrodes and 10 µm diameter recording electrodes were employed in isolated tiger salamander retina electrophysiology studies. Pharmacological agents were used to isolate direct excitation of ganglion cells from excitation of other inner retinal cells. Strength-duration data suggests that if amplitude will be used for the coding of brightness in retinal prostheses, shorter pulses (200 µsec) will allow for a smaller region in the area of the electrode to be excited over a larger dynamic range compared with longer pulses (1 ms). Both electrophysiological results and electrostatic finite-element modeling show that electrode-ele |
| Keyword | retinal prosthesis; neural engineering; electrophysiology |
| 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 |
| Type | texts |
| Legacy record ID | usctheses-m450 |
| Rights | Ahuja, Ashish Kishore |
| 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-Ahuja-20070423 |
| Archival file | uscthesesreloadpub_Volume51/etd-Ahuja-20070423.pdf |
Description
| Title | Page 1 |
| Full text | AN IN VITRO MODEL OF A RETINAL PROSTHESIS by Ashish Kishore Ahuja 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 (ELECTRICAL ENGINEERING) May 2007 Copyright 2007 Ashish Kishore Ahuja |
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