Separation of contamination caused by coil clicks from responses elicited by transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) is accompanied with loud clicks tha t evoke auditory responses in the brain, confounding several types of TMS s tudies. We investigated the effects of these clicks with high-resolution EE G by applying TMS pulses at 3 magnitudes, with the coil placed either at 10 or 50 mm over the subjects' vertex and recording event-related potentials (ERPs). The clicks were found to elicit a positively displaced response at 150-250 ms post-TMS. Furthermore, clicks were found to interact with simult aneously presented auditory sinewave stimuli, resulting in an amplitude dec rease in the auditory N1 response. (C) 1999 Elsevier Science Ireland Ltd. A ll rights reserved.