Abstract
Transcranial magnetic stimulation (TMS) excites neurons in the cortex, and neural activity can be simultaneously recorded using electroencephalography (EEG). However, TMS-evoked EEG potentials (TEPs) do not only reflect transcranial neural stimulation as they can be contaminated by artifacts. Over the last two decades, significant developments in EEG amplifiers, TMS-compatible technology, customized hardware and open source software have enabled researchers to develop approaches which can substantially reduce TMS-induced artifacts. In TMS-EEG experiments, various physiological and external occurrences have been identified and attempts have been made to minimize or remove them using online techniques. Despite these advances, technological issues and methodological constraints prevent straightforward recordings of early TEPs components. To the best of our knowledge, there is no review on both TMS-EEG artifacts and EEG technologies in the literature to-date. Our survey aims to provide an overview of research studies in this field over the last 40 years. We review TMS-EEG artifacts, their sources and their waveforms and present the state-of-the-art in EEG technologies and front-end characteristics. We also propose a synchronization toolbox for TMS-EEG laboratories. We then review subject preparation frameworks and online artifacts reduction maneuvers for improving data acquisition and conclude by outlining open challenges and future research directions in the field.
Highlights
Transcranial magnetic stimulation (TMS) is a non-invasive form of brain stimulation which uses a strong magnetic field to stimulate specific areas of the brain [1]
There are a number of TMS paradigms that are assumed to work over similar physiological cortical properties, which include Quadri-Pulse Stimulation (QPS), transcranial Alternating Current Stimulation, Paired Associative Stimulation (PAS), controllable pulse shape TMS and deep-brain TMS [16,17,18,19,20,21]
When the blinks are synchronous with the TMS pulse, these are overlapped with the first components of the TMS-evoked EEG potentials (TEPs) and, it is difficult to analyze the TEPs during the analysis of the TMS-EEG data [49,68]
Summary
Transcranial magnetic stimulation (TMS) is a non-invasive form of brain stimulation which uses a strong magnetic field to stimulate specific areas of the brain [1]. There are a number of TMS paradigms that are assumed to work over similar physiological cortical properties, which include Quadri-Pulse Stimulation (QPS), transcranial Alternating Current Stimulation (tACS), Paired Associative Stimulation (PAS), controllable pulse shape TMS (cTMS) and deep-brain TMS (dTMS) [16,17,18,19,20,21] These paradigms are usually designed to assess cortical feed forward propriety, instantaneous status, intrinsic oscillatory activity, connectivity and event related response phase dynamics [2,22,23,24]. It is evident from the current literature that TMS has great potential in providing novel insights into the pathophysiology of neurological and psychiatric disorders. TMS-coil related artifacts; Section 5 reports technologies that deal with magnetic artifacts; Section 6 proposes a tool to synchronize TMS laboratory equipment; Section 7 details subject preparation steps to improve TEPs acquisition; Section 8 explores existing challenges and future work and, Section 9 concludes our survey
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