Effect of electrode window size on recording surface potentials in the cortical brain

This study investigated the impact of electrode aperture size on cortical surface potential recordings, focusing on electrocorticography (ECoG) signals and addressing concerns about spatial aliasing and signal amplitude variations in high-density ECoG recordings. Two ECoG electrode arrays with different aperture dimensions (200 µm and 460 µm) were fabricated and tested in the rat visual cortex. Visually evoked potentials (VEPs) were recorded and analyzed for temporal and spatial variations. The results showed that 460 µm-aperture electrodes detected higher amplitude responses in certain regions compared to 200 µm -aperture electrodes, especially for spatially localized VEP peaks. This was attributed to the larger aperture size of the 460 µm electrodes, allowing the detection of VEP components missed by the smaller apertures. These findings align with theoretical considerations, indicating that the electrode aperture size significantly affects the measured signals in ECoG recordings.