Masking the Auditory Evoked Potential in TMS–EEG

Authors: Esther M ter Braack Cecile C de Vos Michel J A M van Putten

Publish Date: 2013/09/01

Volume: 28, Issue: 3, Pages: 520-528

PDF Link

Abstract

There is growing interest in combining transcranial magnetic stimulation TMS with electroencephalography EEG Because TMS pulses are accompanied by a clicking sound it is very likely that part of the response in the EEG consists of an auditory evoked potential AEP Different methods have been applied to mask the sound of TMS However it is unclear which masking method is most effective in reducing the AEP In this study we explore the presumed contribution of the AEP to the response and evaluate different ways to mask the TMS clicking sound Twelve healthy subjects and one completely deaf subject participated in this study Eight different masking conditions were evaluated in nine hearing subjects The amplitude of the N100–P180 complex was compared between the different masking conditions We were not able to completely suppress the N100–P180 when the coil was placed on top of the head Using an earmuff or exposing the subjects to white or adapted noise caused a small but significant reduction in N100–P180 amplitude but the largest reduction was achieved when combining a layer of foam placed between coil and head with white or adapted noise The deaf subject also showed a N100–P180 complex We conclude that both the TMS clicking sound and cortical activation by the magnetic pulse contribute to the N100–P180 amplitude

Keywords: