In Vivo Application of Electrical Rejuvenation Pulses to Chronically Implanted Neural Macroelectrodes in Nonhuman Primates for Regulation of Interface Properties

Abstract

Chronically implanted neural electrodes have become an increasingly important tool in both research and clinical applications, where long-term viability and stability of the electrode-tissue interface (ETI) may be a critical factor in device performance. However, chronic implantation of electrodes in brain tissue typically results in distinct changes to the electrode-tissue interface (ETI), observed as a semicircular arc “tissue component” in Nyquist plots of electrochemical impedance spectroscopy (EIS) measurements. These alterations to electrode-tissue interface properties can interfere with electrode recording characteristics, increase stimulation thresholds, and may create unpredictable behavior in closed-loop applications where neural recordings are used as a control signal. Previous work <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,2</sup> has demonstrated the potential for direct-current electrical rejuvenation to reduce the impact of “tissue component” impedance on measured EIS spectra in microelectrodes chronically implanted in rodents. Our aim here is to further investigate this phenomenon using macroelectrodes in nonhuman primates (NHPs). Scaled versions of human deep brain stimulation (DBS) and electrocorticography (ECoG) electrodes were chronically implanted in an adult male rhesus macaque nonhuman primate. Both direct-current and alternating-current electrical rejuvenation pulses were found to be sufficiently effective at reducing the appearance of “tissue component” in EIS measurements and dropping impedance, with further investigation needed to determine optimal parameters.