Proper reference selection and re-referencing to mitigate bias in single pulse electrical stimulation data
Harvey Huang, Joshua A. Adkinson, Michael A. Jensen, Mohammed A. Hasen, Isabel A. Danstrom, Kelly Rowe Bijanki, Nicholas Miller Gregg, Kai Joshua Miller, Sameer Anil Sheth, Dora Hermes, Eleonora Bartoli · bioRxiv (Cold Spring Harbor Laboratory) · 2024
Abstract Single pulse electrical stimulation experiments produce pulse-evoked potentials used to infer brain connectivity. The choice of recording reference for intracranial electrodes remains non-standardized and can significantly impact data interpretation. When the reference electrode is affected by stimulation or evoked brain activity, it can contaminate the pulse-evoked potentials recorded at all other electrodes and influence interpretation of findings. We highlight this specific issue in intracranial EEG datasets from two subjects recorded at separate institutions. We present several intuitive metrics to detect the presence of reference contamination and offer practical guidance on different mitigation strategies. Either switching the reference electrode or re-referencing to an adjusted common average effectively mitigated the reference contamination issue, as evidenced by increased variability in pulse-evoked potentials across the brain. Overall, we demonstrate the importance of clear quality checks and preprocessing steps that should be performed before analysis of single pulse electrical stimulation data. Highlights A reference electrode close to active tissue can contaminate intracranial EEG signals Interpretation of pulse-evoked potentials can be biased by reference contamination Low response variability between channels is indicative of reference contamination Reference contamination can be resolved through data recollection or re-referencing