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Title: Complex impedance spectroscopy for monitoring tissue responses to inserted neural implants
Authors: Williams, Justin C
Hippensteel, Joseph A
Dilgen, John
Shain, William
Kipke, Daryl R
Issue Date: 1-Dec-2007
Publisher: IOP Publishing Ltd
Citation: Williams, Justin C; Hippensteel, Joseph A; Dilgen, John; Shain, William; Kipke, Daryl R (2007). "Complex impedance spectroscopy for monitoring tissue responses to inserted neural implants." Journal of Neural Engineering. 4(4): 410-423. <http://hdl.handle.net/2027.42/58178>
Abstract: A series of animal experiments was conducted to characterize changes in the complex impedance of chronically implanted electrodes in neural tissue. Consistent trends in impedance changes were observed across all animals, characterized as a general increase in the measured impedance magnitude at 1 kHz. Impedance changes reach a peak approximately 7 days post-implant. Reactive responses around individual electrodes were described using immuno- and histo-chemistry and confocal microscopy. These observations were compared to measured impedance changes. Several features of impedance changes were able to differentiate between confined and extensive histological reactions. In general, impedance magnitude at 1 kHz was significantly increased in extensive reactions, starting about 4 days post-implant. Electrodes with extensive reactions also displayed impedance spectra with a characteristic change at high frequencies. This change was manifested in the formation of a semi-circular arc in the Nyquist space, suggestive of increased cellular density in close proximity to the electrode site. These results suggest that changes in impedance spectra are directly influenced by cellular distributions around implanted electrodes over time and that impedance measurements may provide an online assessment of cellular reactions to implanted devices.
URI: http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db
=pubmed&list_uids=18057508&dopt=citation
ISSN: 1741-2552
DOI: 10.1088/1741-2560/4/4/007
PMID: 18057508
Appears in Collections:Interdisciplinary and Peer-Reviewed
Biomedical Engineering, Department of

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