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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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Autores principales: Rawji, Vishal, Kaczmarczyk, Isabella, Rocchi, Lorenzo, Fong, Po-Yu, Rothwell, John C., Sharma, Nikhil
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998341/
https://www.ncbi.nlm.nih.gov/pubmed/33806701
http://dx.doi.org/10.3390/brainsci11030326
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author Rawji, Vishal
Kaczmarczyk, Isabella
Rocchi, Lorenzo
Fong, Po-Yu
Rothwell, John C.
Sharma, Nikhil
author_facet Rawji, Vishal
Kaczmarczyk, Isabella
Rocchi, Lorenzo
Fong, Po-Yu
Rothwell, John C.
Sharma, Nikhil
author_sort Rawji, Vishal
collection PubMed
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.
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spelling pubmed-79983412021-03-28 Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials Rawji, Vishal Kaczmarczyk, Isabella Rocchi, Lorenzo Fong, Po-Yu Rothwell, John C. Sharma, Nikhil Brain Sci Article 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. MDPI 2021-03-04 /pmc/articles/PMC7998341/ /pubmed/33806701 http://dx.doi.org/10.3390/brainsci11030326 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) ).
spellingShingle Article
Rawji, Vishal
Kaczmarczyk, Isabella
Rocchi, Lorenzo
Fong, Po-Yu
Rothwell, John C.
Sharma, Nikhil
Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials
title 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_short Preconditioning Stimulus Intensity Alters Paired-Pulse TMS Evoked Potentials
title_sort preconditioning stimulus intensity alters paired-pulse tms evoked potentials
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998341/
https://www.ncbi.nlm.nih.gov/pubmed/33806701
http://dx.doi.org/10.3390/brainsci11030326
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