IMPROVING TMS-EEG WITH ULTRA-THIN ACTIVE ELECTRODES

Transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) is a powerful technique to probe cortical excitability and network dynamics, but its broader adoption is limited by long preparation times and strong stimulation-induced artifacts, particularly when using active electrodes. The aim of this study was to evaluate whether ultra-thin active EEG electrodes, combined with hardware- & software-based artifact suppression, can provide reliable and efficient TMS-EEG recordings comparable to the passive gold standard.
We recorded TMS-evoked potentials (TEPs) simultaneously from active and passive electrodes in ten healthy adults during single-pulse stimulation of the left primary motor cortex. A dedicated TMS electrode connector box was used for hardware-level artifact attenuation, followed by a fully automated decay artifact removal algorithm. Signal consistency was quantified using concordance correlation coefficients (CCC) for early (15–80 ms) and late (80–350 ms) TEP components, and amplitude variability was assessed using linear mixed-effects models. Convergence of TEP averages as a function of trial count was also evaluated.
Active and passive electrodes yielded highly similar TEPs, with median CCC values of 0.97 for early and 0.96 for late components. TEP amplitudes decreased systematically with distance from the stimulation site, while electrode type had no significant effect. Both electrode types showed nearly identical convergence behavior, with stable early TEPs achieved after approximately 30 trials.
These findings demonstrate that ultra-thin active electrodes can deliver reliable, physiologically valid TMS-EEG recordings while substantially reducing preparation time. The combination of low-profile hardware and fully automated artifact handling enables fast, reproducible, and scalable TMS-EEG acquisition.