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bioRxiv · 10.64898/2026.05.13.725016

Characterising and Minimising Step and Filtering Artifacts in TMS-EEG Recordings

Holden, M. M.·Goldsworthy, M. R.·Liao, W.-Y.·Clark, S. R.·Cline, C. C.·Keller, C.·Hernandez-Pavon, J. C.·Rogasch, N. C.
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Abstract

Transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) enables direct measurement of cortical reactivity via TMS-evoked potentials (TEPs). Interpretation of early TEP components however, is highly sensitive to stimulation and hardware-related artifacts. We identified and characterised a persistent, non-neural step-drift artifact unexpectedly present in recent TMS-EEG recordings from our group. We show that the artifact is distinct from previously described TMS pulse and discharge/decay artifacts and likely reflects a hardware interaction phenomenon. We demonstrated that amplifier settings, but not TMS pulse shape, substantially influenced artifact expression, with DC-coupled recordings with no online high-pass filter reducing step amplitude compared with AC-coupled recordings with a high-pass filter. Simulations additionally revealed that filtering over the step-drift artifact introduced pronounced ringing and edge artifacts, highlighting the need to address this artifact prior to data processing. We propose a processing pipeline incorporating robust polynomial detrending and a modified Butterworth filter with autoregressive extrapolation that minimised TEP distortion in both simulated and real data containing the step-drift artifact. Together, these findings provide practical recommendations for both preventing and correcting step-drift artifacts and underscore the need for formal definition and routine recognition of this artifact to improve reproducibility and data quality in TMS-EEG research.

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Holden, M. M., Goldsworthy, M. R., Liao, W.-Y., Clark, S. R., Cline, C. C., Keller, C., Hernandez-Pavon, J. C., Rogasch, N. C.. 2026-05-18. Characterising and Minimising Step and Filtering Artifacts in TMS-EEG Recordings. https://doi.org/10.64898/2026.05.13.725016

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