Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials
Motor cortex (M1) paired-pulse TMS (ppTMS) probes excitatory and inhibitory intracortical dynamics by measurement of motor-evoked potentials (MEPs). However, MEPs reflect cortical and spinal excitabilities and therefore cannot isolate cortical function. Concurrent TMS-EEG has the ability to measure...
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doaj-3193471ca9024e50bcd1621902da6ab52021-03-05T00:07:59ZengMDPI AGBrain Sciences2076-34252021-03-011132632610.3390/brainsci11030326Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked PotentialsVishal Rawji0Isabella Kaczmarczyk1Lorenzo Rocchi2Po-Yu Fong3John C. Rothwell4Nikhil Sharma5Department of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKDepartment of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKDepartment of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKDepartment of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKDepartment of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKDepartment of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UKMotor cortex (M1) paired-pulse TMS (ppTMS) probes excitatory and inhibitory intracortical dynamics by measurement of motor-evoked potentials (MEPs). However, MEPs reflect cortical and spinal excitabilities and therefore cannot isolate cortical function. Concurrent TMS-EEG has the ability to measure cortical function, while limiting peripheral confounds; TMS stimulates M1, whilst EEG acts as the readout: the TMS-evoked potential (TEP). Whilst varying preconditioning stimulus intensity influences intracortical inhibition measured by MEPs, the effects on TEPs is undefined. TMS was delivered to the left M1 using single-pulse and three, ppTMS paradigms, each using a different preconditioning stimulus: 70%, 80% or 90% of resting motor threshold. Corticospinal inhibition was present in all three ppTMS conditions. ppTMS TEP peaks were reduced predominantly under the ppTMS 70 protocol but less so for ppTMS 80 and not at all for ppTMS 90. There was a significant negative correlation between MEPs and N45 TEP peak for ppTMS 70 reaching statistical trends for ppTMS 80 and 90. Whilst ppTMS MEPs show inhibition across a range of preconditioning stimulus intensities, ppTMS TEPs do not. TEPs after M1 ppTMS vary as a function of preconditioning stimulus intensity: smaller preconditioning stimulus intensities result in better discriminability between conditioned and unconditioned TEPs. We recommend that preconditioning stimulus intensity should be minimized when using ppTMS to probe intracortical inhibition.https://www.mdpi.com/2076-3425/11/3/326TMSEEGTMS-EEGTEPsshort-interval intracortical inhibitioncortical inhibition |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Vishal Rawji Isabella Kaczmarczyk Lorenzo Rocchi Po-Yu Fong John C. Rothwell Nikhil Sharma |
spellingShingle |
Vishal Rawji Isabella Kaczmarczyk Lorenzo Rocchi Po-Yu Fong John C. Rothwell Nikhil Sharma Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials Brain Sciences TMS EEG TMS-EEG TEPs short-interval intracortical inhibition cortical inhibition |
author_facet |
Vishal Rawji Isabella Kaczmarczyk Lorenzo Rocchi Po-Yu Fong John C. Rothwell Nikhil Sharma |
author_sort |
Vishal Rawji |
title |
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials |
title_short |
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials |
title_full |
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials |
title_fullStr |
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials |
title_full_unstemmed |
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials |
title_sort |
preconditioning stimulus intensity alters paired-pulse tms evoked potentials |
publisher |
MDPI AG |
series |
Brain Sciences |
issn |
2076-3425 |
publishDate |
2021-03-01 |
description |
Motor cortex (M1) paired-pulse TMS (ppTMS) probes excitatory and inhibitory intracortical dynamics by measurement of motor-evoked potentials (MEPs). However, MEPs reflect cortical and spinal excitabilities and therefore cannot isolate cortical function. Concurrent TMS-EEG has the ability to measure cortical function, while limiting peripheral confounds; TMS stimulates M1, whilst EEG acts as the readout: the TMS-evoked potential (TEP). Whilst varying preconditioning stimulus intensity influences intracortical inhibition measured by MEPs, the effects on TEPs is undefined. TMS was delivered to the left M1 using single-pulse and three, ppTMS paradigms, each using a different preconditioning stimulus: 70%, 80% or 90% of resting motor threshold. Corticospinal inhibition was present in all three ppTMS conditions. ppTMS TEP peaks were reduced predominantly under the ppTMS 70 protocol but less so for ppTMS 80 and not at all for ppTMS 90. There was a significant negative correlation between MEPs and N45 TEP peak for ppTMS 70 reaching statistical trends for ppTMS 80 and 90. Whilst ppTMS MEPs show inhibition across a range of preconditioning stimulus intensities, ppTMS TEPs do not. TEPs after M1 ppTMS vary as a function of preconditioning stimulus intensity: smaller preconditioning stimulus intensities result in better discriminability between conditioned and unconditioned TEPs. We recommend that preconditioning stimulus intensity should be minimized when using ppTMS to probe intracortical inhibition. |
topic |
TMS EEG TMS-EEG TEPs short-interval intracortical inhibition cortical inhibition |
url |
https://www.mdpi.com/2076-3425/11/3/326 |
work_keys_str_mv |
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