TMS-induced artifacts on EEG can be reduced by rearrangement of the electrode’s lead wire before recording

OBJECTIVE Our purpose was to establish a technique to reduce residual artifacts after transcranial magnetic stimulation (TMS) from electroencephalographic (EEG) signals. METHODS We investigated the effects of coil direction and stimulus intensity on residual artifacts in an artificial circuit, and tested whether or not the size of the circuit area affects the residual artifact (the model study). Based on the results, the optimization by rearranging the electrode's lead wire was tested on the human scalp (the human study). RESULTS The residual artifact after TMS was dependent on the direction of the figure-of-eight coil, and on the artificial circuit area size. CONCLUSIONS In accordance with the model study, the scalp EEG shows that TMS-induced artifacts can be reduced dramatically before the amplifier input stages in TMS-EEG experiments by a step-wise procedure rearranging the lead wires relative to the fixed coil orientation. SIGNIFICANCE Our technique makes it possible to significantly reduce the residual artifacts from recordings of short-latency TMS-evoked potentials.