The non-transcranial TMS-evoked potential is an inherent source of ambiguity in TMS-EEG studies

Abstract

7Tel: +45 3862 6541; Email: hartwig.siebner@drcmr.dk; http://www.drcmr.dk/siebner 2 8All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/337782 doi: bioRxiv preprint first posted online Jun. 4, 2018; 2 Abstract (246 words) 2 9Transcranial Magnetic Stimulation (TMS) excites populations of neurons in the stimulated cortex, and the 3 0 resulting activation may spread to connected brain regions. The distributed cortical response can be 3 1 recorded with electroencephalography (EEG). Since TMS also stimulates peripheral sensory and motor 3 2 axons and generates a loud "click" sound, the TMS-evoked EEG potential (TEP) not only reflects neural 3 3 activity induced by transcranial neuronal excitation but also neural activity reflecting somatosensory and 3 4 auditory processing. In 17 healthy young individuals, we systematically assessed the contribution of 3 5 multisensory peripheral stimulation to TEPs using a TMS-compatible EEG system. Real TMS was 3 6 delivered with a figure-of-eight coil over the left para-median posterior parietal cortex or superior frontal 3 7 gyrus with the coil being oriented perpendicularly or in parallel to the target gyrus. We also recorded the 3 8 EEG responses evoked by sham stimulation over the posterior parietal and superior frontal cortex, 3 9 mimicking the auditory and somatosensory sensations evoked by real TMS. We applied state-of-the-art 4 0 procedures to attenuate somatosensory and auditory confounds during real TMS, including the placement 4 1 of a foam layer underneath the coil and auditory noise masking. Despite these precautions, the temporal 4 2 and spatial features of the cortical potentials evoked by real TMS at the prefrontal and parietal site closely 4 3 resembled the cortical potentials evoked by realistic sham TMS, both for early and late TEP components. 4Our findings stress the need to include a peripheral multisensory control stimulation in the study design to 4 5 enable a dissociation between truly transcranial and non-transcranial components of TEPs. 4 6 4 7All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

TMS as a pharmacodynamic indicator of cortical activity of a novel anti‐epileptic drug, XEN1101

“…When considering that TMS‐EEG is approaching clinical translation, it must be taken into account that the TMS pulse can induce unwanted somatosensory responses that have an impact on the cortical signal detected with EEG . An online TEP quality control during data collection will be crucial to obtain high‐quality and genuine TMS‐evoked brain responses.…”

Evoked Alpha Power is Reduced in Disconnected Consciousness During Sleep and Anesthesia

“…Other technical constraints should also be noted. A recent study has suggested that some of the TMS-evoked response may be driven by sensory stimulation rather than just direct cortical perturbation 49 . Given that the same stimulation parameters were used in both the wake and disconnected/conscious states it is likely that the relative contribution of transcranial and sensory responses was constant across the states.…”

Brain State-Dependent Brain Stimulation

“…Yet, the most important challenge will be to develop truly closed-loop BSDBS (Figure 1B ) that allows to continuously monitor the brain signals of interest, while concurrently applying NIBS to achieve and maintain the desired brain state and to control perception or behavior. The successful real-time removal of TMS/TCS stimulation artifacts (Walter et al, 2012 ; Herring et al, 2015 ; Rogasch et al, 2017 ) and EEG correlates of multisensory co-stimulation during TMS (Herring et al, 2015 ; Conde et al, in press ) and TCS (Schutter, 2016 ; Herring et al, 2018 ) is therefore a core developmental goal for the near future.…”