Experimental Suppression of TMS-EEG Sensory Potentials

Abstract

AbstractBackgroundThe sensory experience of transcranial magnetic stimulation (TMS) evokes cortical responses measured in EEG that confound interpretation of TMS-evoked potentials (TEPs). Methods for sensory masking have been proposed to minimize sensory contributions to the TEP, but the most effective combination for suprathreshold TMS to dorsolateral prefrontal cortex (dlPFC) is unknown.ObjectiveWe applied sensory suppression techniques and quantified electrophysiology and perception from suprathreshold dlPFC TMS to identify the best combination to minimize the sensory TEP.MethodsIn 21 healthy adults, we applied single pulse TMS at 120% resting motor threshold (rMT) to the left dlPFC and compared EEG vertex N100-P200 and perception. Conditions included three protocols: No masking (no auditory masking, no foam, jittered inter-stimulus interval (ISI)), Standard masking (auditory noise, foam, jittered ISI), and our ATTENUATE protocol (auditory noise, foam, over-the-ear protection, unjittered ISI).ResultsATTENUATE reduced vertex N100-P200 by 56%, “click” loudness perception by 50%, and scalp sensation by 36%. We show that sensory prediction, induced with predictable ISI, has a suppressive effect on vertex N100-P200, and that combining standard suppression protocols with sensory prediction provides the best N100-P200 suppression. ATTENUATE was more effective than Standard masking, which only reduced vertex N100-P200 by 22%, loudness by 27%, and scalp sensation by 24%.ConclusionsWe introduce a sensory suppression protocol superior to Standard masking and demonstrate that using an unjittered ISI can contribute to minimizing sensory confounds. ATTENUATE provides superior sensory suppression to increase TEP signal-to-noise and contributes to a growing understanding of TMS-EEG sensory neuroscience.HighlightsATTENUATE is a novel sensory suppression protocol for suprathreshold dlPFC TMSATTENUATE is superior to standard masking for minimizing sensory confoundsATTENUATE reduced vertex N100-P200 by 56% with no effect on the early TEPATTENUATE reduced “click” loudness rating by 50% and scalp sensation by 36%Individual modifications are not sufficient to reduce vertex N100-P200 or perception