Analyzing Voltage Transients Under Different Stimulation Configurations and Rates in Rat Cortex

Area of Science:

• Neuroscience
• Biomedical Engineering
• Electrophysiology

Background:

• Accurate characterization of neural stimulating electrodes is crucial for effective neuromodulation.
• Existing methods for measuring voltage transients (VTs) can be complex or require specialized equipment.
• Understanding electrode behavior under various stimulation parameters is essential for optimizing device performance.

Purpose of the Study:

• To introduce and validate a simplified method for measuring VTs across different stimulation configurations.
• To investigate the impact of quasi-reference electrode (QRE) polarization on electrode characterization.
• To assess the performance of Utah electrode arrays (UEAs) with sputtered iridium oxide film (SIROF) electrodes and amorphous silicon carbide (a-SiC) encapsulation.

Main Methods:

• Developed a measurement protocol using a standard stimulator, two-electrode setup, and an isolated input oscilloscope.
• Measured VTs in monopolar (MP), bipolar (BP), tripolar (TP), and partial tripolar (PTP) configurations.
• Applied the method to UEAs with SIROF electrodes and a-SiC encapsulation in rat cortex.

Main Results:

• Successfully measured VTs across various stimulation configurations without a potentiostat.
• Demonstrated that QRE polarization leads to an underestimation of maximum charge injection capacity (Q_inj).
• Provided data on electrode performance in vivo at 24 weeks post-implantation.

Conclusions:

• The introduced method offers a practical approach for characterizing neural stimulating electrodes.
• Accounting for QRE polarization is critical for accurate electrode assessment and development.
• Optimizing stimulation protocols is vital for improving clinical outcomes in neural stimulation therapies.