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Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex

Background: Transcranial direct current stimulation (tDCS) is emerging as a promising adjuvant to enhance motor function. However, there has been increasing reservations about the reliability and variability of the neuromodulatory effects evoked by tDCS. Objective/Hypothesis: The main purpose of thi...

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Autores principales: Madhavan, Sangeetha, Sriraman, Aishwarya, Freels, Sally
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039455/
https://www.ncbi.nlm.nih.gov/pubmed/27472368
http://dx.doi.org/10.3390/brainsci6030026
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author Madhavan, Sangeetha
Sriraman, Aishwarya
Freels, Sally
author_facet Madhavan, Sangeetha
Sriraman, Aishwarya
Freels, Sally
author_sort Madhavan, Sangeetha
collection PubMed
description Background: Transcranial direct current stimulation (tDCS) is emerging as a promising adjuvant to enhance motor function. However, there has been increasing reservations about the reliability and variability of the neuromodulatory effects evoked by tDCS. Objective/Hypothesis: The main purpose of this study was to explore the test-retest reliability and inter-individual variability of tDCS of the lower limb M1 and the relationship between transcranial magnetic stimulation (TMS)-related measures and tDCS-induced changes. Methods: Fifteen healthy participants received anodal tDCS of the lower limb M1 either when performing a lower limb motor task or when the limb was at rest. Each condition was tested twice. tDCS induced changes in corticomotor excitability of the tibialis anterior muscle were measured using TMS. A repeated measures ANOVA was performed to examine efficacy of tDCS between the two task conditions. Intraclass correlation coefficients (ICC) and variance component analyses were performed to examine reliability and variability respectively. Results: A significant increase in in corticomotor excitability was noted for the tDCS-task condition at 140% active motor threshold (AMT) and when comparing recruitment curve slopes, but not at 120% and 130% AMT. Overall, ICC values between testing days for each stimulation condition ranged from 0.6–0.9. Higher ICCs were seen for higher TMS intensities (140% AMT) and recruitment curve slopes. Inter-individual variability contributed to 34% of the exhibited variance. Conclusions: Our data suggest that the TMS-related measure used to assess neuromodulation after tDCS has an effect on its perceived test-retest reliability and inter-individual variability. Importantly, we noticed that a high reliability and low variability does not necessarily indicate clinical efficacy of tDCS as some participants showed little to no modulation of corticomotor excitability consistently.
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spelling pubmed-50394552016-10-04 Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex Madhavan, Sangeetha Sriraman, Aishwarya Freels, Sally Brain Sci Article Background: Transcranial direct current stimulation (tDCS) is emerging as a promising adjuvant to enhance motor function. However, there has been increasing reservations about the reliability and variability of the neuromodulatory effects evoked by tDCS. Objective/Hypothesis: The main purpose of this study was to explore the test-retest reliability and inter-individual variability of tDCS of the lower limb M1 and the relationship between transcranial magnetic stimulation (TMS)-related measures and tDCS-induced changes. Methods: Fifteen healthy participants received anodal tDCS of the lower limb M1 either when performing a lower limb motor task or when the limb was at rest. Each condition was tested twice. tDCS induced changes in corticomotor excitability of the tibialis anterior muscle were measured using TMS. A repeated measures ANOVA was performed to examine efficacy of tDCS between the two task conditions. Intraclass correlation coefficients (ICC) and variance component analyses were performed to examine reliability and variability respectively. Results: A significant increase in in corticomotor excitability was noted for the tDCS-task condition at 140% active motor threshold (AMT) and when comparing recruitment curve slopes, but not at 120% and 130% AMT. Overall, ICC values between testing days for each stimulation condition ranged from 0.6–0.9. Higher ICCs were seen for higher TMS intensities (140% AMT) and recruitment curve slopes. Inter-individual variability contributed to 34% of the exhibited variance. Conclusions: Our data suggest that the TMS-related measure used to assess neuromodulation after tDCS has an effect on its perceived test-retest reliability and inter-individual variability. Importantly, we noticed that a high reliability and low variability does not necessarily indicate clinical efficacy of tDCS as some participants showed little to no modulation of corticomotor excitability consistently. MDPI 2016-07-27 /pmc/articles/PMC5039455/ /pubmed/27472368 http://dx.doi.org/10.3390/brainsci6030026 Text en © 2016 by the authors; 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/).
spellingShingle Article
Madhavan, Sangeetha
Sriraman, Aishwarya
Freels, Sally
Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title_full Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title_fullStr Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title_full_unstemmed Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title_short Reliability and Variability of tDCS Induced Changes in the Lower Limb Motor Cortex
title_sort reliability and variability of tdcs induced changes in the lower limb motor cortex
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039455/
https://www.ncbi.nlm.nih.gov/pubmed/27472368
http://dx.doi.org/10.3390/brainsci6030026
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