Current neuroprosthetic systems based on electrophysiological recording have an extended, yet finite working lifetime. Some posited lifetime-extension solutions involve improving device biocompatibility or suppressing host immune responses. Our objective was to test an alternative solution comprised of applying a voltage pulse to a microelectrode site, herein termed "rejuvenation." Previously, investigators have reported preliminary electrophysiological results by utilizing a similar voltage pulse. In this study we sought to further explore this phenomenon via two methods: 1) electrophysiology; 2) an equivalent circuit model applied to impedance spectroscopy data. The experiments were conducted via chronically implanted silicon-substrate iridium microelectrode arrays in the rat cortex. Rejuvenation voltages resulted in increased unit recording signal-to-noise ratios (10% ± 2%), with a maximal increase of 195% from 3.74 to 11.02. Rejuvenation also reduced the electrode site impedances at 1 kHz (67% ± 2%). Neither the impedance nor recording properties of the electrodes changed on neighboring microelectrode sites that were not rejuvenated. In the equivalent circuit model, we found a transient increase in conductivity, the majority of which corresponded to a decrease in the tissue resistance component (44% ± 7%). These findings suggest that rejuvenation may be an intervention strategy to prolong the functional lifetime of chronically implanted microelectrodes.
Bibliographical noteFunding Information:
Manuscript received October 12, 2004; revised May 1, 2005. This work was supported in part by the Defense Advanced Research Projects Agency under Grant DARPA: N66001-02-C-8059, in part by the Center for Neural Communication Technology under Grant P41-EB00230, and in part by the Engineering Research Centers program of the National Science Foundation (NSF) under Award EEC-9986866. Asterisk indicates corresponding author. *K. J. Otto is with the Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109 USA (e-mail: firstname.lastname@example.org).
- Brain-machine interface
- Chronic recording