Electrical rejuvenation of chronically implanted macroelectrodes in nonhuman primates

Area of Science:

• Neuroscience
• Biomedical Engineering
• Implantable Electrode Technology

Background:

• Chronic implantation of brain electrodes leads to changes in the electrode-tissue interface (ETI), increasing impedance and degrading signal quality.
• These ETI changes negatively impact signal-to-noise ratio (SNR) for recordings and energy delivery for stimulation, crucial for closed-loop systems.
• Previous studies showed electrical rejuvenation can restore SNR in rodent microelectrodes, but its efficacy in large animal models with clinical macroelectrodes was untested.

Purpose of the Study:

• To test electrical rejuvenation's effectiveness in clinically relevant macroelectrode designs in a large animal model (nonhuman primates).
• To characterize parameters for optimizing AC and DC electrical rejuvenation methods.
• To longitudinally assess the impact of rejuvenation on the electrode-tissue interface (ETI) using electrochemical impedance spectroscopy (EIS).

Main Methods:

• Evaluated AC and DC electrical rejuvenation on epidural electrocorticography (ECoG) and deep-brain stimulation (DBS) electrodes chronically implanted in nonhuman primates (NHP).
• Utilized electrochemical impedance spectroscopy (EIS) to measure impedance and characterize the ETI before, after, and longitudinally post-rejuvenation.
• Employed stochastic error modeling and Kramers-Kronig relations to assess impedance data reliability and measurement stationarity.

Main Results:

• Both AC and DC electrical rejuvenation rapidly reduced electrode impedance and the tissue component of the ETI across all tested electrode types.
• DC and low-frequency AC rejuvenation demonstrated the most significant impedance reductions and ETI improvements, observable in Nyquist plots.
• The beneficial effects of a single rejuvenation session persisted for several days to over a week, with no adverse behavioral changes observed in the NHP.

Conclusions:

• Electrical rejuvenation is effective in mitigating chronic ETI changes in NHP using clinically relevant macroelectrode designs.
• This technique offers a viable strategy to maintain electrode performance for long-term neural recording and stimulation applications.
• The findings provide crucial preliminary data for translating electrical rejuvenation to human clinical applications.